Regulation of vitamin B6 metabolism in human red cells

To assess vitamin B6 nutritional status, the effects of a dietary supplementation of pyridoxine on aspartate aminotransferase (EGOT) and the role of pyridoxine kinase (PnK) in this enzymatic process were studied in 6 subjects. Various dosages of pyridoxine were administered over a prolonged period; blood samples were taken at various times and red blood cells age-segregated by density centrifugation. It was found that enzyme activity increased with pyridoxine supplementation and that activity was related to dose level. The greatest increase in EGOT activity was in the young cells and correlated to PnK activity. Human red blood cell metabolism and the levels of pyridoxal 5-phosphate can be altered by B6 vitamin administration, though the total effect is time dependent. The complexity of the process is shown in the different mechanisms triggered by the nature of the B6 vitamin and must be considered in the use of EGOT in determining vitamin B6 nutrition status