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Abstract

Two different pathways, pathway I and II, for vitamin B-6 degradation are known in bacteria. Pyridoxamine-pyruvate transaminase and pyridoxine 4-oxidase, respectively, use pyridoxamine and pyridoxine as a substrate in pathway I of vitamin B-6 degradation. Among 500 bacterial isolates, four isolates, T2, T4, T5, and T6, were identified as the fast growing bacterial isolates using pyridoxine as a carbon source. The activities of pyridoxine 4-oxidase and pyridoxamine-pyruvate transaminase were determined by analyzing the reaction product, pyridoxal, by isocratic reverse-phase HPLC. Only two isolates, T2 and T6, showed pyridoxine 4-oxidase activities of 4.08 and 9.38 Unit/mg (pmol/min/mg protein), respectively. The activity of pyridoxamine-pyruvate transaminase was 6.31 Unit/mg in T2 isolate and 6.11 Unit/mg in T6 isolate. Some biochemical characteristics and nucleotide sequences (500 bases) of 16S rDNA suggested that T2 and T6 were closely related to Ochrobactrum anthropi and Enterobacter cloacae, respectively. This is the first report of pyridoxamine-pyruvate transaminase and pyridoxine 4-oxidase, enzymes in vitamin B-6 degradation pathway in O. anthropi and E. cloacae-like bacteria.