Vitamin B-6 Degradation by Pyridoxamine-Pyruvate Transaminase and Pyridoxine 4-Oxidase from Ochrobactrum anthropi and Enterobacter cloacae-like Bacteria

Trongpanich Yanee,^a* Niamsanit Suwanna^b, and Siri Sineenat^a

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.

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a Department of Biochemistry, Faculty of Science, Khon Kaen University, Khon Khaen 40002, Thailand.
b Department of Microbiology, Faculty of Science, Khon Kaen University, Khon Khaen 40002, Thailand.

* Corresponding author, E-mail: yantro@kku.ac.th

Received 13 Jun 2004, Accepted 23 Mar 2005