Streptomyces beta-alanine:alpha-ketoglutarate aminotransferase, a novel omega-amino acid transaminase. Purification, crystallization, and enzymologic properties.

K Yonaha,K Suzuki,S Toyama

doi:10.1016/s0021-9258(19)83615-3

Abstract

An enzyme which catalyzes the transamination of beta-alanine with alpha-ketoglutarate was purified to homogeneity from Streptomyces griseus IFO 3102 and crystallized. Molecular weight of the enzyme was found to be 185,000 +/- 10,000 by a gel-filtration method. The enzyme consists of four subunits identical in molecular weight (51,000 +/- 1,000). The transaminase is composed of 483 amino acids/subunit containing 7 and 8 residues of half-cystine and methionine, respectively. The enzyme exhibits absorption maxima at 278 and 415 nm. The pyridoxal 5'-phosphate content was determined to be 4 mol/mol of enzyme. The enzyme catalyzes transamination of omega-amino acids including taurine and hypotaurine. beta-Alanine and DL-beta-aminoisobutyrate served as a good amino donor; the Michaelis constants are 8.0 and 12.5 mM, respectively. alpha-Ketoglutarate is the only amino acceptor (Km = 4.0 mM); pyruvate and oxalacetate are inactive. Based on the substrate specificity, the terminology of beta-alanine:alpha-ketoglutarate transaminase is proposed for the enzyme. Carbonyl reagents, HgCl2,DL-gabaculine, and alpha-fluoro-beta-alanine strongly inhibited the enzyme.

Highlights

An enzyme whichcatalyzesthe transamination o8f- ologic properties.’ The purified transaminase, has alanine with a-ketoglutaratewas purified to homoge- low activity for 8-alanine, suggesting the presence of another neity from Streptomyces griseus IF0 3102 and crys- enzyme in the actinomycetes which catalyzes the transamitallized
The substrate specificity, the terminology of @-alanine:a- investigation has revealed that two enzymes are mainly conketoglutaratetransaminase is proposedforthe en- cerned with the transamination of &alanine and y-aminozyme
Two w-amino acid transaminases are mainly involved in hand, fungal and mammalian y-aminobutyratea-ketoglutarthe metabolism of 8-alanine, i.e. /3-alanine-pyruvate amino- atetransaminases catalyze the transamination of both W

Summary

Introduction

An enzyme whichcatalyzesthe transamination o8f- ologic properties.’ The purified transaminase, has alanine with a-ketoglutaratewas purified to homoge- low activity for 8-alanine, suggesting the presence of another neity from Streptomyces griseus IF0 3102 and crys- enzyme in the actinomycetes which catalyzes the transamitallized. Based on the substrate specificity, the enzyme was found to be a novel w-aminoacid transaminase. The enzyme catalyzes transamination ofw-amino acids including tau- A-Keto- A considerable effort has been devoted to the characteriglutarate is the only amino acceptor (K,= 4.0 mM); zation of w-amino acid transaminase, a key enzyme involved pyruvate and oxalacetate are inactive.

Results

Conclusion