The release of glucokinase (hexokinase IV) from digitonin-permeabilized hepatocytes from rat, guinea pig or mouse liver is inhibited by physiological concentrations of Mg2+ (> 0.25 mM). Preincubation of hepatocytes with fructose increases glucokinase release during permeabilization in the presence of Mg2+ but decreases glucokinase release in the absence of Mg2+, suggesting that fructose causes ...

A human liver glucokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) cDNA was isolated from a liver cDNA library. This cDNA (hLGLK1) appeared to be full length [2548 base pairs (bp) plus additional poly(A) residues], as its size was consistent with a single 2.8-kilobase (kb) glucokinase mRNA on Northern blot analysis of liver poly(A)+ RNA. The cDNA contained an open reading frame of 1392 b...

his journal’s editors have asked me to comment on the paper in this issue by Jetton et al. entitled "Substrate induced nuclear export and peripheral compartmentalization of hepatic glucokinase correlates with glycogen deposition." The investigations of these authors exemplify the remarkable recent trend in studies of intermediary metabolism paying careful attention to the precise intracellular ...

Glucokinase is a monomeric protein under native and denaturating conditions yet presents a sigmoidal saturation function for glucose. These peculiarities suggested the possibility that polymerization occurs under assay conditions. Thus the apparent molecular weight of glucokinase was determined by gel filtration at 4°C and at 30°C in the presence of substrates and products, singly and in combin...

Epinephrine, norepinephrine, and isoproterenol prevent the induction of rat liver glucokinase (EC 2.7.1.2) produced by the administration of glucose to animals with low levels of the enzyme. The low levels of glucokinase were obtained by feeding the animals a carbohydrate-free diet for 6 days. When epinepbrine was given 4 hours after the administration of carbohydrate there was only a slight in...

Phosphoinositide-dependent kinase-1 (PDK1) is implicated in the metabolic effects of insulin as a key mediator of phosphoinositide 3-kinase-dependent signaling. Here we show that mice with liver-specific PDK1 deficiency manifest various defects in the metabolic actions of insulin in the liver as well as a type 2 diabetes-like phenotype characterized by marked hyperinsulinemia and postprandial h...

During a recent investigation of the persistence of substrate ambiguity in contemporary enzymes, we identified three distinct ambiguous sugar kinases embedded within the modern Escherichia coli genome [Miller, B. G., and Raines, R. T. (2004) Biochemistry 43, 6387-6392]. These catalysts are the YajF, YcfX, and NanK polypeptides, all of which possess rudimentary glucokinase activities. Here, we r...