A new cofactor in prokaryotic enzyme: Tryptophan tryptophylquinone as the redox prosthetic group in methylamine dehydrogenase

Journal Article · Fri May 10 00:00:00 EDT 1991 · Science (Washington, D.C.); (United States)

DOI:https://doi.org/10.1126/science.2028257· OSTI ID:6097736

McIntire, W S ^[1]; Wemmer, D E ^[2]; Chistoserdov, A; Lidstrom, M E ^[3]

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1. Dept. of Veterans Affairs Medical Center, San Francisco, CA (United States) Univ. of California, San Francisco (United States)
2. Univ. of California, Berkeley (United States)
3. W. M. Keck Labs., Pasadena, CA (United States)

Methylamine dehydrogenase (MADH), an {alpha}{sub 2}{beta}{sub 2} enzyme from numerous methylotrophic soil bacteria, contains a novel quinonoid redox prosthetic group that is covalently bound to its small {beta} subunit through two amino acyl residues. A comparison of the amino acid sequence deduced from the gene sequence of the small subunit for the enzyme from Methylobacterium extorquens AM1 with the published amino acid sequence obtained by Edman degradation method, allowed the identification of the amino acyl constituents of the cofactor as two tryptophyl residues. This information was crucial for interpreting {sup 1}H and {sup 13}C nuclear magnetic resonance, and mass spectral data collected for the semicarbazide- and carboxymethyl-derivatized bis(tripeptidyl)-cofactor of MADH from bacterium W3A1. The cofactor is composed of two cross-linked tryptophyl residues. Although there are many possible isomers, only one is consistent with all the data: The first tryptophyl residue in the peptide sequence exists as an indole-6,7-dione, and is attached at its 4 position to the 2 position of the second, otherwise unmodified, indole side group. Contrary to earlier reports, the cofactor of MADH is not 2,7,9-tricarboxypyrroloquinoline quinone (PQQ), a derivative thereof, of pro-PQQ. This appears to be the only example of two cross-linked, modified amino acyl residues having a functional role in the active site of an enzyme, in the absence of other cofactors or metal ions.

• DOE Contract Number: FG05-86ER75281
• OSTI ID: 6097736
• Journal Information: Science (Washington, D.C.); (United States), Vol. 252:5007; ISSN 0036-8075
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
METHYLAMINE
REDOX REACTIONS
OXIDOREDUCTASES
BACTERIA
EXPERIMENTAL DATA
QUINONES
SOILS
TRYPTOPHAN
AMINES
AMINO ACIDS
AROMATICS
AZAARENES
AZOLES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DATA
ENZYMES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INDOLES
INFORMATION
MICROORGANISMS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PROTEINS
PYRROLES
550200* - Biochemistry