Phosphorylation of yeast hexokinases.
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 (bcy1) lacking a regulatory subunit, and increased labeling during growth with high concentrations of glucose in a strain attenuated in the catalytic subunit (tpk1w1). 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.
Vojtek
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Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115.
Fraenkel
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D000242:Cyclic AMP / Q000494:pharmacology; D005941:Glucokinase / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006593:Hexokinase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
D010750:Phosphoproteins; D000242:Cyclic AMP; D006593:Hexokinase; D005941:Glucokinase; D005947:Glucose