Expression and activity of hexokinase in the early mouse embryo

Houghton, F.D., Sheth, Bhavwanti, Moran, B., Leese, H.J. and Fleming, T.P. (1996) Expression and activity of hexokinase in the early mouse embryo. Molecular Human Reproduction, 2 (10), 793-798. (doi:10.1093/molehr/2.10.793).

Abstract

The maximal activity and Michaelis constant, KM, of hexokinase have been measured in the peri-implantation mouse embryo using an ultramicrofluorescence technique. In addition, transcript detection of the predominant isoenzyme hexokinase I has been determined in single preimplantation mouse embryos at successive stages of development using reverse transcriptase-mediated cDNA amplification. Maximal hexokinase activity decreased dramatically peri-implantation, from 0.97 ± 0.19 nmol/μg protein/h at the blastocyst stage to 0.31 ± 0.05 nmol/μg protein/h on day 6.5. The KM remained relatively low and constant over this period (0.23–0.39 mM), indicating the absence of the hexokinase type IV isoenzyme. The pattern of hexokinase activity resembled that of glucose consumption suggesting a possible regulatory role for the enzyme during this period of development. Hexokinase I mRNA was detected in the oocyte and all preimplantation stages of development. The blastocyst polymerase chain reaction (PCR) product, when cloned and sequenced was found to be 98% homologous with mouse tumour hexokinase I. Taken together, these data suggest that the hexokinase gene is not under transcriptional control during early mouse embryo development but plays a significant role in the regulation of glucose consumption. A role for hexokinase in the phosphate-induced inhibition of early embryo development is also proposed.

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Contributors

Author: F.D. Houghton

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