Red cell uridine monophosphate kinase: effects of red cell aging on the activity of two UMPK gene products.

We have previously reported that uridine monophosphate kinase (UMPK) is genetically polymorphic in man, and that the UMPK2 gene product has less activity than that of UMPK1 when measured in normal red cells. In this paper we present evidence that the activity of UMPK, like that of many other enzymes, declines during red cell aging, and that the lower activity of UMPK 2, as compared with UMPK 1, is best explained by its more rapid catabolism.