Phosphorylation of yeast hexokinases

Authors


Correspondence to D. G. Fraenkel, Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA

Abstract

We show by the use of 32P-labeling in vivo that hexokinase 2 and hexokinase 1 in Saccharomyces cerevisiae are phosphoproteins. The highest labeling was after incubation in medium with a low concentration of glucose, when labeling appears to be predominant even without use of immunoprecipitation. The nature of the modification is not known, but it has properties consistent with a phosphomonoester of serine or threonine. The cAMP-dependent protein kinase plays a negative role in hexokinase phosphorylation, in that there was reduced labeling in strains (bcyl) lacking a regulatory subunit, and increased labeling during growth with high concentrations of glucose in a strain attenuated in the catalytic subunit (tpklw1). The function of the modification is not known, but there was a correlation between the extent of labeling and the expression of kinase-dependent high-affinity glucose uptake.

Enzyme
 

Hexokinase (EC 2.7.1.1)

Ancillary