Lysine degradation in Candida. Characterization and probable role of l-norleucine-leucine, 4-aminobutyrate and σ-aminovalerate: 2-oxoglutarate aminotransferases

Abstract

Three enzymes partially purified that catalyze respectively the transamination of l-norleucine, 4-aminobutyrate and σ-aminovalerate with α-ketoglutarate as aminoacceptor were characterized and isolated from l-lysine adapted cell of Candida guilliermondii var. membranaefaciens. The transaminases have a maximum activity in the pH range of 7.8–8.5 and at 55°C, 45°C and 40°C respectively. α-Ketoglutarate and to a lesser extent pyridoxal-5′-phosphate were effective protecting agents against rise in temperature. The enzymes exhibit absorption maximum at 280 nm, 330 nm and 410 nm. The fact that l-norleucine-leucine aminotransferase, 4-aminobutyrate aminotransferase and σ-aminovalerate aminotransferase are strongly induced by growing the yeast Candida on l-lysin suggests new hypothetic pathways for the catabolism of l-lysine where the main substrate of each aminotransferase could be an intermediary metabolite.