Purification and characterization of an inducible L-lysine: 2-oxoglutarate 6-aminotransferase from Candida utilis

Abstract

L-Lysine:2-oxoglutarate 6-aminotransferase (EC 2.1.6.36) was purified 202-fold from the yeast Candida utilis. The subunit Mr estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis was 40 kDa. The Mr of the native enzyme was estimated to be 83 kDa by gel filtration, suggesting a dimeric structure. The enzyme exhibits absorption maxima at 280, 340 and 420 nm, and binds 2 mol pyridoxal-5-phosphate/mol of the native enzyme. The aminotransferase has a maximum activity at pH 8.5 and at 4 degrees C. 2-Oxoglutarate is the best amino acceptor with L-lysine as amino donor. Lower activity is observed with oxaloacetate (38%), pyruvate (19%) and 2-oxoadipate (7%) as acceptor or with L-thialysine (13%) as donor. The Km values are 2.5 mM for L-lysine, 3.8 mM for 2-oxoglutarate and 0.015 mM for pyridoxal-5-phosphate. The enzyme activity is induced in cells grown in the presence of L-lysine.