Trypanosoma brucei brucei: uptake and metabolism of pyridoxine and pyridoxal

The uptake and metabolism of the B6 vitamers pyridoxine and pyridoxal by T. brucei (TREU 55) was investigated. The results show that these vitamers are taken up by simple diffusion followed by metabolic trapping. Both pyridoxine and pyridoxal were found to be metabolised to pyridoxal phosphate in whole cells. The majority of pyridoxal taken up appears to remain as pyridoxal (perhaps protein bound) the remainder being slowly phosphorylated to pyridoxal phosphate by pyridoxal kinase. The majority of pyridoxine taken up was found to be rapidly metabolised to pyridoxal. Evidence was also found supporting the hypothesis that pyridoxine may be phosphorylated to pyridoxal phosphate and then rapidly converted to pyridoxal phosphate.