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Information on EC 1.4.9.1 - methylamine dehydrogenase (amicyanin)
for references in articles please use BRENDA:EC1.4.9.1
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EC Tree 1 Oxidoreductases
1.4 Acting on the CH-NH2 group of donors
1.4.9 With a copper protein as acceptor
1.4.9.1 methylamine dehydrogenase (amicyanin)
IUBMB Comments
Contains tryptophan tryptophylquinone (TTQ) cofactor. The enzyme oxidizes aliphatic monoamines and diamines, histamine and ethanolamine, but not secondary and tertiary amines, quaternary ammonium salts or aromatic amines.
The expected taxonomic range for this enzyme is: Bacteria, Eukaryota
- 1.4.9.1
- tryptophylquinone
- ttq
- paracoccus
- denitrificans
- maug
-
quinoproteins
-
diheme
- versutus
-
bis-feiv
-
protein-derived
- methylobacterium
-
premadh
-
thiobacillus
-
davidson
-
interprotein
- extorquens
- azurins
- quinol
-
six-electron
-
substrate-derived
-
reorganizational
- n-methylglutamate
- n-butylamine
-
diferrous
-
aminoquinols
-
high-valence
- methylomonas
-
mathews
- analysis
Reaction Schemes
show+
+
2
amicyanin
=
+
+
2
reduced amicyanin
Synonyms
methylamine dehydrogenase, quinohemoprotein amine dehydrogenase, qhndh, heme 2, qh-amdh, sqh-amdh, quinohemoprotein amine dehydrogenases, primary-amine dehydrogenase, quinohaemoprotein amine dehydrogenase, more
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SYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
amine: oxidoreductase (acceptor deaminating)
-
-
-
-
dehydrogenase, amine
-
-
-
-
EC 1.4.98.1
-
-
formerly
-
EC 1.4.99.3
-
-
formerly
-
MADH
methylamine dehydrogenase
primary-amine dehydrogenase
-
-
-
-
QH-AmDH
QHNDH
quinohemoprotein amine dehydrogenase
MADH
-
-
-
-
MADH
-
-
methylamine dehydrogenase
-
-
-
-
methylamine dehydrogenase
-
-
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
methylamine + H2O + 2 amicyanin = formaldehyde + NH3 + 2 reduced amicyanin
-
-
-
-
methylamine + H2O + 2 amicyanin = formaldehyde + NH3 + 2 reduced amicyanin
in the rate-determining step, a proton is transferred from the methyl group of the substrate to residue D76. Only one of the oxygen atoms of D76 can act as an acceptor of the proton, the other interacts with T122 via a strong hydrogen bond
-
methylamine + H2O + 2 amicyanin = formaldehyde + NH3 + 2 reduced amicyanin
model of electron transfer reaction between enzyme and transfer protein amicyanin
-
methylamine + H2O + 2 amicyanin = formaldehyde + NH3 + 2 reduced amicyanin
reduction of Cu2+ of electron transfer protein amicyanin by enzyme is a true electron transfer reaction
-
methylamine + H2O + 2 amicyanin = formaldehyde + NH3 + 2 reduced amicyanin
the rate-determining step in the reductive half-reaction of the bacterial enzyme methylamine dehydrogenase is the proton abstraction from the native substrate methylamine, ab initio QM/MM molecular dynamics simulations, average flow of electronic charge within the QM subsystem during proton transfer to OD1 computed from randomly selected subsets of the reactant, model comparisons, detailed overview
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
oxidation
-
-
-
-
oxidative deamination
-
-
-
-
redox reaction
-
-
-
-
reduction
-
-
-
-
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PATHWAY SOURCE
PATHWAYS
MetaCyc
methylamine degradation I
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SYSTEMATIC NAME
IUBMB Comments
methylamine:amicyanin oxidoreductase (deaminating)
Contains tryptophan tryptophylquinone (TTQ) cofactor. The enzyme oxidizes aliphatic monoamines and diamines, histamine and ethanolamine, but not secondary and tertiary amines, quaternary ammonium salts or aromatic amines.
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CAS REGISTRY NUMBER
COMMENTARY
55476-92-1
-
60496-14-2
-
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
LITERATURE
COMMENTARY
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
1,12-diaminododecane + acceptor + H2O
? + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
1,6-diaminohexane + acceptor + H2O
?
-
Substrates: acceptor: phenazine ethosulfate/2,6-dichlorophenolindophenol
Products: -
Products: -
?
1,7-diaminoheptane + acceptor + H2O
?
-
Substrates: acceptor: phenazine ethosulfate/2,6-dichlorophenolindophenol
Products: -
Products: -
?
1-aminopentane + acceptor + H2O
pentanal + NH3 + reduced acceptor
-
Substrates: acceptor: phenazine ethosulfate/2,6-dichlorophenolindophenol
Products: -
Products: -
?
12-aminododecane + acceptor + H2O
dodecanal + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
2-phenylethylamine + 2 H2O + 2 acceptor
2-phenylacetic acid + NH3 + 2 reduced acceptor
-
Substrates: primary amine
Products: -
Products: -
?
2-phenylethylamine + acceptor + H2O
2-phenylacetaldehyde + NH3 + reduced acceptor
-
Substrates: acceptor: phenazine ethosulfate/2,6-dichlorophenolindophenol
Products: -
Products: -
?
benzylamine + H2O + ferricyanide
benzaldehyde + NH3 + reduced ferricyanide
-
Substrates: -
Products: -
Products: -
?
dithionite + amicyanin + H2O
?
-
Substrates: two-electron-reduced MADH is obtained by exposing the enzyme either to a 3fold molar excess of methylamine or to 2 mM dithionite
Products: -
Products: -
?
histamine + acceptor + H2O
? + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
methylamine + amicyanin + H2O
formaldehyde + NH3 + reduced amicyanin
-
Substrates: -
Products: -
Products: -
?
methylamine + H2O + 2,6-dichloroindophenol
formaldehyde + NH3 + reduced 2,6-dichloroindophenol
-
Substrates: -
Products: -
Products: -
r
methylamine + H2O + 2,6-dichloroindophenol + phenazine ethosulfate
formaldehyde + NH3 + reduced phenazine ethosulfate + ?
-
Substrates: -
Products: -
Products: -
r
methylamine + H2O + amicyanin
formaldehyde + NH3 + reduced amicyanin
Substrates: -
Products: -
Products: -
?
methylamine + H2O + cytochrome c-550
formaldehyde + NH3 + reduced cytochrome c-550
-
Substrates: -
Products: -
Products: -
r
methylamine + H2O + K3Fe(CN)6
formaldehyde + NH3 + reduced K3Fe(CN)6
-
Substrates: -
Products: -
Products: -
r
n-butylamine + H2O + ferricyanide
butanal + NH3 + reduced ferricyanide
-
Substrates: -
Products: -
Products: -
?
n-nonylamine + acceptor + H2O
nonanal + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
n-pentylamine + acceptor + H2O
pentanal + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
benzylamine + acceptor + H2O
benzaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
benzylamine + acceptor + H2O
benzaldehyde + NH3 + reduced acceptor
-
Substrates: acceptor: phenazine ethosulfate/2,6-dichlorophenolindophenol
Products: -
Products: -
?
benzylamine + acceptor + H2O
benzaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
benzylamine + acceptor + H2O
benzaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
butylamine + acceptor + H2O
butanal + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
butylamine + acceptor + H2O
butanal + NH3 + reduced acceptor
-
Substrates: acceptor: phenazine ethosulfate/2,6-dichlorophenolindophenol
Products: -
Products: -
?
butylamine + acceptor + H2O
butanal + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
butylamine + acceptor + H2O
butanal + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
ethylamine + acceptor + H2O
acetaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
ethylamine + acceptor + H2O
acetaldehyde + NH3 + reduced acceptor
-
Substrates: acceptor: phenazine ethosulfate/2,6-dichlorophenolindophenol
Products: -
Products: -
?
methylamine + acceptor + H2O
formaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
methylamine + acceptor + H2O
formaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
methylamine + acceptor + H2O
formaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
methylamine + acceptor + H2O
formaldehyde + NH3 + reduced acceptor
-
Substrates: acceptor: amicyanin
Products: -
Products: -
?
methylamine + acceptor + H2O
formaldehyde + NH3 + reduced acceptor
-
Substrates: acceptor: phenazine ethosulfate/2,6-dichlorophenolindophenol
Products: -
Products: -
?
methylamine + acceptor + H2O
formaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
methylamine + acceptor + H2O
methanal + NH3 + reduced acceptor
Mycobacterium convolutum
-
Substrates: -
Products: -
Products: -
?
methylamine + acceptor + H2O
methanal + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
methylamine + acceptor + H2O
methanal + NH3 + reduced acceptor
-
Substrates: acceptor: phenazine ethosulfate/2,6-dichlorophenolindophenol or amicyanin
Products: -
Products: -
?
methylamine + acceptor + H2O
methanal + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
methylamine + amicyanin + H2O
formaldehyde + reduced amicyanin + NH3
-
Substrates: amicyanin is the in vivo electron acceptor
Products: -
Products: -
?
methylamine + amicyanin + H2O
formaldehyde + reduced amicyanin + NH3
-
Substrates: two-electron-reduced MADH is obtained by exposing the enzyme either to a 3fold molar excess of methylamine or to 2 mM dithionite. The complex of MADH and amicyanin in solution is studied using nuclear magnetic resonance. Signals of perdeuterated, 15N-enriched amicyanin bound to MADH are observed. Chemical shift perturbation analysis indicates that the dissociation rate constant is 250/sec and that amicyanin assumes a well-defined position in the complex in solution. The most affected residues are in the interface observed in the crystal structure, whereas smaller chemical shift changes extend to deep inside the protein
Products: -
Products: -
?
methylamine + H2O + 2 amicyanin
formaldehyde + NH3 + 2 reduced amicyanin
Substrates: -
Products: -
Products: -
?
methylamine + H2O + 2 amicyanin
formaldehyde + NH3 + 2 reduced amicyanin
Substrates: -
Products: -
Products: -
?
methylamine + H2O + 2 amicyanin
formaldehyde + NH3 + 2 reduced amicyanin
-
Substrates: -
Products: -
Products: -
?
methylamine + H2O + amicyanin
formaldehyde + ammonia + reduced amicyanin
-
Substrates: electron transfer from MADH to cytochrome c-551i does not involve a ternary complex but occurs via a ping-pong mechanism in which amicyanin uses the same interface for the reactions with MADH and cytochrome c-551i. Amicyanin binds tightly to MADH with an interface that matches the one observed in the crystal structure and that mostly overlaps with the binding site for cytochrome c-551i. Amicyanin can react rapidly with cytochrome c-551i, but association of amicyanin with MADH inhibits this reaction
Products: -
Products: -
?
methylamine + H2O + amicyanin
formaldehyde + ammonia + reduced amicyanin
-
Substrates: P96A and P96G mutations in amycyanin do not affect the spectroscopic or redox properties of amicyanin but increase the Kd value for complex formation with MADH and alter the kinetic mechanism for the interprotein elcetron transfer reaction. The crystal structure of P96G amicyanin is very similar to that of native amicyanin, but in addition to the change in Pro96, the side chains of residues Phe97 and Arg99, which make contacts with MADH that are important for stabilizing the amicyanin-MADH complex, are oriented differently
Products: -
Products: -
?
n-hexylamine + acceptor + H2O
hexanal + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
n-hexylamine + acceptor + H2O
hexanal + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
phenylethylamine + acceptor + H2O
phenylacetaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
phenylethylamine + acceptor + H2O
phenylacetaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
phenylethylamine + acceptor + H2O
phenylacetaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
propylamine + acceptor + H2O
propionaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
propylamine + acceptor + H2O
propionaldehyde + NH3 + reduced acceptor
-
Substrates: acceptor: phenazine ethosulfate/2,6-dichlorophenolindophenol
Products: -
Products: -
?
propylamine + acceptor + H2O
propionaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
propylamine + acceptor + H2O
propionaldehyde + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: acceptor 2,6-dichlorophenolindophenol
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: acceptor phenazine ethosulfate or amicyanin
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: acceptor potassium ferricyanide, phenazine ethosulfate, 2,6-dichlorophenolindophenol
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: acceptor potassium ferricyanide, phenazine ethosulfate, 2,6-dichlorophenolindophenol
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: -
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: acceptor cytochrome c-550
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: acceptor phenazine methosulfate
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: acceptor 2,6-dichlorophenol-indophenol, ferricyanide or cytochrome c
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: cytochrome c or artificial electron acceptor
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: acceptor 2,6-dichlorophenolindophenol
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: acceptor phenazine methosulfate
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: acceptor 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide and potassium ferricyanide
Products: -
Products: -
?
RCH2NH2 + acceptor + H2O
RCHO + NH3 + reduced acceptor
-
Substrates: acceptor phenazine methosulfate
Products: -
Products: -
?
additional information
?
-
Mycobacterium convolutum
-
Substrates: broad specificity
Products: -
Products: -
?
additional information
?
-
-
Substrates: amicyanin ami catalyzes the electron transfer from MADH to the terminal oxidase, without the need for any c-type cytochrome. In the absence of either MADH or cytochrome aa3, amicanin is not capable of oxygen reduction on the same time scale. The oxygen consumption depends nearly linearly on the amicyanin concentration up to at least 100 microM. Experiments demonstrate a remarkable number of possibilities for the electron transfer. The interactions appear to be governed exclusively by the electrostatic nature of each of the proteins. Paracoccus denitrificans provides a pool of cytochromes for efficient electron transfer via weak, ill-defined interactions
Products: -
Products: -
?
additional information
?
-
Substrates: methylamine dehydrogenase (MADH) requires the cofactor tryptophan tryptophylquinone (TTQ) for activity
Products: -
Products: -
?
additional information
?
-
-
Substrates: not: FMN, NAD+, NADP+
Products: -
Products: -
?
additional information
?
-
-
Substrates: little or no activity with isoamines, L-ornithine, L-lysine and certain diamines or polyamines
Products: -
Products: -
?
additional information
?
-
-
Substrates: an essential enzyme for the aerobic degradation of many primary amines even though they have quite different chemical structures (aromatic or aliphatic)
Products: -
Products: -
?
additional information
?
-
-
Substrates: when different QHNDH mutants (peaA, peaC and peaD) are transformed with a genetic construction containing the peaABCD cluster, all the recombinant strains efficiently catabolized 2-phenylethylamine as well as other primary amines like propyl-, butyl- and pentylamine.
Products: -
Products: -
?
additional information
?
-
-
Substrates: nonspecific oxidizing both short and long primary monoamines and diamines, polyamines, L-noradrenaline, histamine, benzylamine and di-n-hexylamine
Products: -
Products: -
?
additional information
?
-
-
Substrates: nonspecific oxidizing both short and long primary monoamines and diamines, polyamines, L-noradrenaline, histamine, benzylamine and di-n-hexylamine
Products: -
Products: -
?
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NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
LITERATURE
COMMENTARY
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
2-phenylethylamine + 2 H2O + 2 acceptor
2-phenylacetic acid + NH3 + 2 reduced acceptor
-
Substrates: primary amine
Products: -
Products: -
?
methylamine + amicyanin + H2O
formaldehyde + reduced amicyanin + NH3
-
Substrates: amicyanin is the in vivo electron acceptor
Products: -
Products: -
?
methylamine + H2O + amicyanin
formaldehyde + NH3 + reduced amicyanin
Substrates: -
Products: -
Products: -
?
methylamine + H2O + 2 amicyanin
formaldehyde + NH3 + 2 reduced amicyanin
Substrates: -
Products: -
Products: -
?
methylamine + H2O + 2 amicyanin
formaldehyde + NH3 + 2 reduced amicyanin
Substrates: -
Products: -
Products: -
?
methylamine + H2O + 2 amicyanin
formaldehyde + NH3 + 2 reduced amicyanin
-
Substrates: -
Products: -
Products: -
?
additional information
?
-
-
Substrates: amicyanin ami catalyzes the electron transfer from MADH to the terminal oxidase, without the need for any c-type cytochrome. In the absence of either MADH or cytochrome aa3, amicanin is not capable of oxygen reduction on the same time scale. The oxygen consumption depends nearly linearly on the amicyanin concentration up to at least 100 microM. Experiments demonstrate a remarkable number of possibilities for the electron transfer. The interactions appear to be governed exclusively by the electrostatic nature of each of the proteins. Paracoccus denitrificans provides a pool of cytochromes for efficient electron transfer via weak, ill-defined interactions
Products: -
Products: -
?
additional information
?
-
-
Substrates: an essential enzyme for the aerobic degradation of many primary amines even though they have quite different chemical structures (aromatic or aliphatic)
Products: -
Products: -
?
additional information
?
-
-
Substrates: when different QHNDH mutants (peaA, peaC and peaD) are transformed with a genetic construction containing the peaABCD cluster, all the recombinant strains efficiently catabolized 2-phenylethylamine as well as other primary amines like propyl-, butyl- and pentylamine.
Products: -
Products: -
?
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
quinoid cofactor
-
alpha subunit contains unknown quinoid cofactor
-
quinone
-
contains a quinone similar to but not identical with the prosthetic group of EC 1.1.99.8
cysteine tryptophylquinone
-
cofactor is derived from a pair of gene-encoded amino acids by post-translational modification
cysteine tryptophylquinone
-
This enzyme contains an unusual redox cofactor (CTQ) and two hemes acting as redox active groups
heme c
-
two heme c cofactors mediate the transfer of the substrate-derived electrons from cysteine tryptophylquinone to an external electron acceptor
tryptophan tryptophylquinone
-
-
tryptophan tryptophylquinone
-
contains a tryptophan tryptophylquinone prosthetic group
tryptophan tryptophylquinone
-
each beta-subunit possesses a prosthetic group
tryptophan tryptophylquinone
-
a two-electron redox cofactor, each beta subunit of the heterotetrameric enzyme NADH possesses a tryptophan tryptophylquinone, TTQ, protein-derived cofactor. TTQ is formed by post-translational modification of two tryptophan residues of the preMADH polypeptide chain through the diheme enzyme MauG. This six-electron oxidation of preMADH requires long-range electron transfer as the structure of the MauG-preMADH complex reveals that the shortest distance between the modified residues of preMADH and the nearest heme of MauG is 14.0 A, overview
tryptophan tryptophylquinone
-
MauG is a diheme enzyme that catalyzes the final steps in the biosynthesis of the cofactor tryptophan tryptophylquinone in the enzyme
tryptophan tryptophylquinone
TTQ, methylamine dehydrogenase requires the cofactor tryptophan tryptophylquinone for activity. TTQ is a posttranslational modification that results from an 8-electron oxidation of two specific tryptophans in the MADH beta-subunit, betaTrp57 and betaTrp108. The final 6-electron oxidation is catalyzed by the unusual c-type di-heme enzyme, MauG. The di-ferric enzyme can react with H2O2, but atypically for c-type hemes the di-ferrous enzyme can react with O2 as well. In both cases, an unprecedented bis-Fe(IV) redox state is formed, composed of a ferryl heme (Fe(IV)=O) and the second heme as Fe(IV) stabilized by His-Tyr axial ligation. Bis-Fe(IV) MauG acts as a potent 2-electron oxidant. Catalysis is long-range and requires a hole hopping electron transfer mechanism. TTQ structure analysis, overview
tryptophan tryptophylquinone
TTQ, the catalytic cofactor of enzyme MADH. Activator enzyme MauG is involved in TTQ biosynthesis. Mutation of Trp93 of MauG to tyrosine causes loss of bound Ca2+ and alters the kinetic mechanism of tryptophan tryptophylquinone cofactor biosynthesis. The substrate for MauG-dependent TTQ biosynthesis is preMADH
tryptophan tryptophylquinone
TTQ, the catalytic cofactor of enzyme MADH. It is not an exogenous cofactor but is instead derived from posttranslational modifications of the beta subunits of MADH
tryptophan tryptophylquinone
TTQ, the catalytic cofactor of enzyme MADH. It is not an exogenous cofactor but is instead derived from posttranslational modifications of the beta subunits of MADH as evidenced from the crystal structure of MADH. Kinetic mechanism of MauG-dependent TTQ biosynthesis, overview
tryptophan tryptophylquinone
TTQ, the quinone cofactor of the enzyme. QhpG is involved in the quinone cofactor formation
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Ca2+
Co2+
KCl
-
the rate of transfer of the first electron from methylamine-reduced MADH to amicyanin is increased by monovalent cations
Mn2+
Na+
additional information
additional information
-
monovalent cations affect spectral properties and rate of gated electron transfer from reduced enzyme to electron acceptor
additional information
-
cations inhibit reduction of oxidized MADH at pH 8, monovalent cations increase oxidation rate, divalent cations decrease oxidation rate
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INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
amicyanin mutant M98K
-
mutant acts as a competitive inhibitor in the reaction of native amicyanin with methylamine dehydrogenase indicating that the M98K mutation has not affected the affinity for its natural electron donor. The crystal structure of M98K amicyanin reveals an overall structure very similar to native amicyanin but the type I binding site is occupied by zinc instead of copper
-
cyclopropylamine
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mechanism-based inhibitor. The resulting inactivation is accompanied by the formation of a covalent cross-link between the alpha and beta subunits of the enzyme. No cross-linking is seen with mutant enzymes alphaF55A or alphaF55I mutant enzymes. With mutant enzyme alphaF55E cross-linking of subunits is observed
additional information
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immobilized enzyme: little change in sensitivity to inhibition
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phenylhydrazine
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O6 of cysteine tryptophylquinone is the site of inhibitory attack by phenylhydrazine
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
Dithionite
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rapidly activates sQH-AmDH, activation process involves a reduction process
dithiothreitol
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rapidly activates sQH-AmDH, activation process involves a reduction process
additional information
the gene which encodes MauG is located in the methylamine utilization (mau) gene cluster of several gram negative bacteria. The mau cluster contains the two structural genes for MADH as well as accessory proteins that are required for MADH biogenesis
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MauG
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the inactive 119 kDa heterotetrameric precursor of MADH with incompletely synthesized tryptophan tryptophylquinone can be converted to active MADH with mature tryptophan tryptophylquinone in vitro by reaction with MauG, a 42 kDa diheme enzyme
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MauG
42 kDa activator enzyme of methylamine dehydrogenase, the MauG residue Gln103 is important for the redox properties and stability of MauG. The diheme enzyme MauG catalyzes a six electron oxidation that is required for the posttranslational modification of a precursor of methylamine dehydrogenase (preMADH) to complete the biosynthesis of its protein-derived cofactor, tryptophan tryptophylquinone (TTQ). The substrate for MauG that undergoes this posttranslational modification is a precursor protein of MADH (preMADH). It possesses a monohydroxylated residue betaTrp57. The reactions catalyzed by MauG occur in the following order: covalent cross-linking of monohydroxylated betaTrp57 to betaTrp108, incorporation of a second oxygen atom into the side chain of betaTrp57, and oxidation of the quinol species to the quinone. Catalysis requires long-range electron transfer because preMADH does not make direct contact with either heme of MauG. The electron transfer occurs via a hole-hopping mechanism in which Trp residues of MauG are reversibly oxidized. Steady-state kinetic parameters of the MauG-dependent biosynthesis of TTQ from preMADH, overview. Analysis of effects of the Q103 mutations on the visible absorption spectra of the diferric and diferrous redox states of MauG
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MauG
a diheme enzyme, the diheme enzyme MauG catalyzes oxidative post-translational modifications of a protein substrate, precursor protein of methylamine dehydrogenase (preMADH), that binds to the surface of MauG. The high-spin heme iron of MauG is located 40A from preMADH. The ferric heme is an equilibrium of five- and six-coordinate states. PreMADH binding increases the proportion of five-coordinate heme three-fold. On reaction of MauG with H2O2 both hemes become FeIV. In the absence of preMADH the hemes autoreduce to ferric heme in a multistep process involving multiple electron and proton transfers. Binding of preMADH in the absence of catalysis alters the mechanism of autoreduction of the ferryl heme. Substrate binding alters the environment in the distal heme pocket of the high-spin heme over very long distance. MauG structure, PDB ID 3L4M. Kinetics overview
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MauG
pre-enzyme MADH and its activator MauG perform a distinct form of enzyme catalysis that requires multi-step hole hopping-mediated long range electron transfer, mechanism, overview. The distance between the modified residues of preMADH and the nearest heme iron of MauG is 19 A, which is still a relatively long distance for biological electron transfer. MauG behaves more like a b-type heme enzyme than a c-type heme enzyme. Residue Trp93 and the bound Ca2+ are also components of the diheme cofactor. Ca2+ is positioned in the vicinity of the two hemes and is connected to each heme via H-bonding networks that include bound waters. Ca2+-depleted MauG shows no TTQ biosynthesis activity and exhibits altered absorbance, EPR and resonance Raman spectral properties. Re-addition of Ca2+ fully restores activity and the native spectral properties. Residue Pro107 is critical in maintaining the properstructure of the distal heme pocket of the high-spin heme of MauG to allow oxygen to bind. Trp199 of MauG, which resides at the MauG-preMADH interface, is positioned midway between the residues on preMADH that are modified and the nearest heme. Kinetic mechanism of MauG-dependent TTQ biosynthesis, overview
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MauG
the di-heme enzyme is required for methylamine dehydrogenase maturation. MauG is highly unusual in that the di-ferrous c-type heme redox state can also bind and activate O2. Mixing preMADH with either di-ferric MauG and H2O2 or di-ferrous MauG and O2, leads to fully active MADH. Thus, MauG represents the final enzyme in MADH maturation, catalyzing a 6-electron oxidation to complete tryptophan tryptophyquinone, TTQ, biosynthesis. Upon reaction of di-ferric MauG with H2O2, an unprecedented high-valent species is formed, which Mossbauer spectroscopy showed contains both MauG hemes in the Fe(IV) oxidation state. Analysis of the crystal structure of MauG in complex with preMADH at 2.1 resolution, overview. MauG reaction mechanism and kinetics with preMADH and H2O2. MauG-dependent completion of TTQ biosynthesis requires a hole hopping electron transfer mechanism. Structure-function analysis. The MauG Y294H variant is unable to catalyze TTQ biosynthesis
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MauG
the diheme enzyme MauG catalyses a six-electron oxidation required for post-translational modification of preMADH (precursor of methylamine dehydrogenase) to complete the biosynthesis of its tryptophan tryptophylquinone, TTQ, cofactor. mutation of Trp93 of MauG to tyrosine causes loss of bound Ca2+ and alters the kinetic mechanism of tryptophan tryptophylquinone cofactor biosynthesis, overview. Whereas Ca2+-depleted wild-type MauG is inactive, W93Y MauG exhibits TTQ biosynthesis activity, although with much lower rate and highly unusual kinetic behaviour. The steady-state reaction exhibits a long lag phase, the duration of which is dependent on the concentration of preMADH, kinetic modeling. Analysis of th structures of Trp93 and Ca2+ site in MauG
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE