Characterization of a novel enzyme, N6-acetyl-L-lysine: 2-oxoglutarate aminotransferase, which catalyses the second step of lysine catabolism in Candida maltosa.

A novel aminotransferase catalyzing the second step of lysine catabolism, the oxidative transamination of the alpha-group of N6-acetyllysine, was identified and characterized in the yeast Candida maltosa. The enzyme was strongly induced in cells grown on L-lysine as sole carbon source. Its activity was specific for both N6-acetyllysine and 2-oxoglutarate. The Km values were 14 mM for the donor, 4 mM for the acceptor and 1.7 microM for pyridoxal-5-phosphate. The enzyme had a maximum activity at pH 8.1 and 32 degrees C. Its molecular mass estimated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis was 55 kDa. Since the native molecular mass determined by gel filtration was 120 kDa, the enzyme is probably a homodimer.