Pyridoxal kinase: decreased activity in red blood cells of Afro-Americans.

The mean pyridoxal kinase activity in red blood cells of American blacks was approximately 50 percent lower than that of American whites. Lymphocytes, granulocytes, and cultured skin fibroblasts from black and white donors contained identical pyridoxal kinase activity. The pyridoxal kinase of blacks was indistinguishable from that of whites with respect to heat stability, chromatographic mobility on microgranular diethylaminoethyl cellulose, Michaelis-Menten constant for pyridoxine, and susceptibility to inhibition by 4-deoxypyridoxine. The difference of the activity of this enzyme in whites and in blacks is much greater than any previously observed biochemical difference between the races.