The level, intracellular distribution, and isozymic pattern of hexokinase (EC 18.104.22.168) were determined on human chorionic villi obtained by trophoblast biopsy in the first trimester of pregnancy. About 50% of total hexokinase activity was found to be particle-bound and 96% of this in the overt form (i.e. assayable without the addition of detergents). Both soluble and particulate hexokinase show the same affinities for glucose but differ in the affinity for MgATP2- and in their sensitivity to glucose 1,6-diphosphate inhibition. By chromatographic and kinetic methods the soluble hexokinase was found to be represented by isozymes I, II and traces of hexokinase III while most of the bound enzyme was hexokinase type I. These results provide evidence for the expression of at least three hexokinase isozymes in early human development and can partially explain the high rate of glucose utilization of the placenta.
- chorionic villi
- human trophoblast
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health