Streptomyces beta-alanine:alpha-ketoglutarate aminotransferase, a novel omega-amino acid transaminase. Purification, crystallization, and enzymologic properties.
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.
D000612:4-Aminobutyrate Transaminase / Q000302:isolation & purification*; D000596:Amino Acids / Q000032:analysis; D003460:Crystallization; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D008970:Molecular Weight; D011732:Pyridoxal Phosphate / Q000032:analysis; D013302:Streptomyces / Q000201:enzymology*; D013379:Substrate Specificity; D013696:Temperature
D000596:Amino Acids; D046911:Macromolecular Substances; D011732:Pyridoxal Phosphate; D000612:4-Aminobutyrate Transaminase