J. Biol. Chem., Vol. 260, Issue 6, 3265-3268, Mar, 1985
Streptomyces beta-alanine:alpha-ketoglutarate aminotransferase, a novel omega-amino acid transaminase. Purification, crystallization, and enzymologic properties
K Yonaha, K Suzuki and S Toyama
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.
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