Glucose-phosphorylating enzymes of Candida yeasts and their regulation in vivo.
Three glucose-phosphorylating enzymes having different specificities for glucose and fructose were separated from the cell-free extract of Candida tropicalis by means of ammonium sulfate fractionation and chromatography on DEAE-cellulose and Sephadex G-100. Two of them, which phosphorylated fructose 1.5 times faster than glucose, were designated as hexokinase I and II (ATP : D-hexose 6-phosphotransferase, EC 2.7.1.1.), and the other with very low or no fructose-phosphorylating activity, as glucokinase (ATP : D-glucose 6-phosphotransferase, EC 2.7.1.2). Km values for glucose with both hexokinase I and glucokinase were 0.3 mM, and that for fructose with hexokinase I was 2.2 mM. Time-course changes in the levels of these enzymes in C. tropicalis growing on glucose and on n-alkane revealed that hexokinase was induced specifically by the sugars, while glucokinase was a constitutive enzyme. Addition of cycloheximide to the culture medium prevented the increase in the hexose-phosphorylating activity and in the Fru/Glu ratio (the ratio of enzymatic phosphorylation of fructose to that of glucose) in the cells. Although Candida lipolytica also contained hexokinase and glucokinase, both enzymes seemed to be constitutive.
D000085:Acetates / Q000378:metabolism; D000473:Alkanes / Q000378:metabolism; D002175:Candida / Q000201:enzymology*; D003513:Cycloheximide / Q000494:pharmacology; D000431:Ethanol / Q000378:metabolism; D005632:Fructose / Q000378:metabolism; D005941:Glucokinase / Q000302:isolation & purification / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006593:Hexokinase / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics
D000085:Acetates; D000473:Alkanes; D005632:Fructose; D000431:Ethanol; D003513:Cycloheximide; D006593:Hexokinase; D005941:Glucokinase; D005947:Glucose