Publications

• Purification and kinetic characterization of a specific glucokinase from Streptococcus mutans OMZ70 cells.

  Porter E.V., Chassy B.M., Holmlund C.E.

  Glucokinase (ATP-D-glucose 6-phosphotransferase, EC 2.7.1.2) was purified 144-fold from extracts of sucrose-grown Streptococcus mutans OMZ70 (ATCC 33535) cells. Twenty compounds were tested as potential substrates; only glucose (Km = 0.61 mM) was phosphorylated. The reaction catalyzed by the purif ... >> More

  Glucokinase (ATP-D-glucose 6-phosphotransferase, EC 2.7.1.2) was purified 144-fold from extracts of sucrose-grown Streptococcus mutans OMZ70 (ATCC 33535) cells. Twenty compounds were tested as potential substrates; only glucose (Km = 0.61 mM) was phosphorylated. The reaction catalyzed by the purified enzyme was dependent on the presence of glucose, nucleoside triphosphate and metal ion; glucose 6-phosphate and ADP were the products. Of the seven nucleoside triphosphates tested, ATP (Km = 0.21 mM) was the most efficient phosphate donor in the enzyme-catalyzed formation of glucose 6-phosphate. Both Mn2+ (relative activity, 173%) and Co2+ (264%) were more efficient than Mg2+ (100%) in supporting the enzyme reaction. The enzyme exhibited a broad maximal activity in the pH range from 7.5 to 9.5. The apparent molecular weight of glucokinase, as determined by gel filtration, was 41 000. With glucose held constant at either saturating or subsaturating levels, ADP was a noncompetitive inhibitor of ATP (Ki = 0.67 mM). ADP was an uncompetitive inhibitor of glucose (Ki = 0.71 mM) when ATP was held constant at either a saturating or subsaturating concentration. Glucose 6-phosphate was a competitive inhibitor of glucose (Ki = 0.31 mM) at saturating ATP and exhibited noncompetitive or mixed inhibition at a subsaturating ATP concentration. Glucose 6-phosphate was not an inhibitor toward ATP at saturating glucose concentrations, but exhibited noncompetitive inhibition at subsaturating glucose concentrations. The kinetic data support the postulation of a sequential mechanism for the glucokinase reaction; they are consistent with an ordered mechanism in which glucose binds first and glucose 6-phosphate dissociates last. Furthermore, the data suggest the existence of more than one enzyme binding site for the substrates of the glucokinase reaction. << Less

  Biochim Biophys Acta 709:178-186(1982) [PubMed] [EuropePMC]

• Glucokinase of Dictyostelium discoideum.

  Baumann P.

  Biochemistry 8:5011-5015(1969) [PubMed] [EuropePMC]

• Mammalian glucokinase and its gene.

  Iynedjian P.B.

  Biochem J 293:1-13(1993) [PubMed] [EuropePMC]

• Biochemical basis of glucokinase activation and the regulation by glucokinase regulatory protein in naturally occurring mutations.

  Heredia V.V., Carlson T.J., Garcia E., Sun S.

  Glucokinase (GK) has several known polymorphic activating mutations that increase the enzyme activity by enhancing glucose binding affinity and/or by alleviating the inhibition of glucokinase regulatory protein (GKRP), a key regulator of GK activity in the liver. Kinetic studies were undertaken to ... >> More

  Glucokinase (GK) has several known polymorphic activating mutations that increase the enzyme activity by enhancing glucose binding affinity and/or by alleviating the inhibition of glucokinase regulatory protein (GKRP), a key regulator of GK activity in the liver. Kinetic studies were undertaken to better understand the effect of these mutations on the enzyme mechanism of GK activation and GKRP regulation and to relate the enzyme properties to the associated clinical phenotype of hypoglycemia. Similar to wild type GK, the transient kinetics of glucose binding for activating mutations follows a general two-step mechanism, the formation of an enzyme-glucose complex followed by an enzyme conformational change. However, the kinetics for each step differed from wild type GK and could be grouped into specific types of kinetic changes. Mutations T65I, Y214C, and A456V accelerate glucose binding to the apoenzyme form, whereas W99R, Y214C, and V455M facilitate enzyme isomerization to the active form. Mutations that significantly enhance the glucose binding to the apoenzyme also disrupt the protein-protein interaction with GKRP to a large extent, suggesting these mutations may adopt a more compact conformation in the apoenzyme favorable for glucose binding. Y214C is the most active mutation (11-fold increase in k(cat)/K(0.5)(h)) and exhibits the most severe clinical effects of hypoglycemia. In contrast, moderate activating mutation A456V nearly abolishes the GKRP inhibition (76-fold increase in K(i)) but causes only mild hypoglycemia. This suggests that the alteration in GK enzyme activity may have a more profound biological impact than the alleviation of GKRP inhibition. << Less

  J. Biol. Chem. 281:40201-40207(2006) [PubMed] [EuropePMC]

• Molecular and cellular regulation of human glucokinase.

  Sternisha S.M., Miller B.G.

  Glucose metabolism in humans is tightly controlled by the activity of glucokinase (GCK). GCK is predominantly produced in the pancreas, where it catalyzes the rate-limiting step of insulin secretion, and in the liver, where it participates in glycogen synthesis. A multitude of disease-causing muta ... >> More

  Glucose metabolism in humans is tightly controlled by the activity of glucokinase (GCK). GCK is predominantly produced in the pancreas, where it catalyzes the rate-limiting step of insulin secretion, and in the liver, where it participates in glycogen synthesis. A multitude of disease-causing mutations within the gck gene have been identified. Activating mutations manifest themselves in the clinic as congenital hyperinsulinism, while loss-of-function mutations produce several diabetic conditions. Indeed, pharmaceutical companies have shown great interest in developing GCK-associated treatments for diabetic patients. Due to its essential role in maintaining whole-body glucose homeostasis, GCK activity is extensively regulated at multiple levels. GCK possesses a unique ability to self-regulate its own activity via slow conformational dynamics, which allows for a cooperative response to glucose. GCK is also subject to a number of protein-protein interactions and post-translational modification events that produce a broad range of physiological consequences. While significant advances in our understanding of these individual regulatory mechanisms have been recently achieved, how these strategies are integrated and coordinated within the cell is less clear. This review serves to synthesize the relevant findings and offer insights into the connections between molecular and cellular control of GCK. << Less

  Arch Biochem Biophys 663:199-213(2019) [PubMed] [EuropePMC]