Relationships between the age-dependent decay of glucose-1,6-bisphosphate synthesis, phosphoribomutase and phosphoglucomutase in human red cells

Abstract

In human red blood cells phosphoglucomutase exists in multiple molecular forms with different isoelectric points determined by two distinct loci called PGM 1 and PGM 2. With regard to the phosphoglucomutase PGM 1 and PGM 2 isoenzymes, the latter appear to be more important in erythrocyte metabolism owing to their ability to mutate ribose monophosphates and synthetize glucose-1,6-bisphosphate. In this paper we show that, beside undergoing age-related postranslational modifications, both phosphoglucomutase PGM 1 and PGM 2 forms decrease their activities as the mean cell age increases. Under the experimental conditions used to separate erythrocytes by age the comparison of the younger erythrocytes with the older shows that total phosphoglucomutase, phosphoribomutase and glucose-1,6-biphosphate synthetic activities decay by 55%, 26% and 28%, respectively. We consider that these results substantiate the multifunctionality of PGM 2 isoenzymes. Furthermore we discuss the role of these forms in the age-related decay of erythrocyte metabolism.