Purification and characterization of a dimeric phenylalanine dehydrogenase from Rhodococcus maris K-18

J Bacteriol. 1989 Jan;171(1):30-6. doi: 10.1128/jb.171.1.30-36.1989.

Abstract

NAD+-dependent phenylalanine dehydrogenase (EC 1.4.1.) was purified to homogeneity from a crude extract of Rhodococcus maris K-18 isolated from soil. The enzyme had a molecular mass of about 70,000 daltons and consisted of two identical subunits. The enzyme catalyzed the oxidative deamination of L-phenylalanine and several other L-amino acids and the reductive amination of phenylpyruvate and p-hydroxyphenylpyruvate. The enzyme required NAD+ as a natural coenzyme. The NAD+ analog 3-acetylpyridine-NAD+ showed much greater coenzyme activity than did NAD+. D-Phenylalanine, D-tyrosine, and phenylethylamine inhibited the oxidative deamination of L-phenylalanine. The enzyme reaction was inhibited by p-chloromercuribenzoate and HgCl2. Initial-velocity and product inhibition studies showed that the reductive amination proceeded through a sequential ordered ternary-binary mechanism. NADH bound first to the enzyme, followed by phenylpyruvate and then ammonia, and the products were released in the order L-phenylalanine and NAD+. The Michaelis constants were as follows: L-phenylalanine, 3.8 mM; NAD+, 0.25 mM; NADH, 43 microM; phenylpyruvate, 0.50 mM; and ammonia, 70 mM.

MeSH terms

  • Amino Acid Oxidoreductases / isolation & purification*
  • Amino Acid Oxidoreductases / metabolism
  • Bacterial Proteins / genetics*
  • Chromatography
  • Chromatography, Ion Exchange
  • Durapatite
  • Hydroxyapatites
  • Kinetics
  • Macromolecular Substances
  • Molecular Weight
  • Rhodopseudomonas / classification
  • Rhodopseudomonas / enzymology*
  • Substrate Specificity

Substances

  • Bacterial Proteins
  • Hydroxyapatites
  • Macromolecular Substances
  • Durapatite
  • Amino Acid Oxidoreductases
  • phenylalanine oxidase