Conversion of methylamine dehydrogenase to a long-chain amine dehydrogenase by mutagenesis of a single residue

Biochemistry. 2000 Sep 19;39(37):11184-6. doi: 10.1021/bi001568n.


Methylamine dehydrogenase (MADH) is a tryptophan tryptophylquinone (TTQ) dependent enzyme that catalyzes the oxidative deamination of primary amines. Amino acid residues of both the TTQ-bearing beta subunit and the noncatalytic alpha subunit line a substrate channel that leads from the protein surface to the enzyme active site. Phe55 of the alpha subunit is located at the opening of the active site. Conversion of alphaPhe55 to alanine dramatically alters the substrate preference of MADH. The K(m) for methylamine increases from 9 microM to 15 mM. The preferred substrates are now primary amines with chain lengths of at least seven carbons. The K(m) for 1, 10-diaminodecane is 11 microM, compared to 1.2 mM for wild-type MADH. Despite the large variation in K(m) values, k(cat) values are relatively unaffected by the mutation. Molecular modeling of substrates into the crystal structure of the enzyme active site and substrate channel provides an explanation for the dramatic changes in substrate specificity caused by this mutation of a single amino acid residue.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alanine / genetics
  • Amino Acid Substitution / genetics*
  • Kinetics
  • Models, Molecular
  • Mutagenesis, Site-Directed*
  • Oxidoreductases Acting on CH-NH Group Donors / chemistry*
  • Oxidoreductases Acting on CH-NH Group Donors / genetics*
  • Paracoccus denitrificans / enzymology
  • Paracoccus denitrificans / genetics
  • Phenylalanine / genetics
  • Substrate Specificity / genetics
  • Tyrosine / genetics


  • Tyrosine
  • Phenylalanine
  • methylamine dehydrogenase
  • Oxidoreductases Acting on CH-NH Group Donors
  • quinohemoprotein amine dehydrogenase
  • Alanine