Insights Into the Biochemical and Genetic Basis of Glucokinase Activation From Naturally Occurring Hypoglycemia Mutations

• Published in: Diabetes (New York, N.Y.) Vol. 52; no. 9; pp. 2433 - 2440
• Main Authors: GLOYN, Anna L, NOORDAM, Kees, MATSCHINSKY, Franz M, HATTERSLEY, Andrew T, WILLEMSEN, Michèl A. A. P, ELLARD, Sian, LAM, Wayne W. K, CAMPBELL, Ian W, MIDGLEY, Paula, SHIOTA, Chyio, BUETTGER, Carol, MAGNUSON, Mark A
• Format: Journal Article
• Language: English
• Published: Alexandria, VA American Diabetes Association 01.09.2003
• Subjects: Adolescent; Age; Amino acids; Biological and medical sciences; Birth weight; Diabetes; Diabetes. Impaired glucose tolerance; DNA Mutational Analysis; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Enzymes; Families & family life; Genetic aspects; Genotype & phenotype; Glucokinase - chemistry; Glucokinase - genetics; Glucokinase - metabolism; Glucose; Glucose metabolism; Histology; Humans; Hypoglycemia; Hypoglycemia - enzymology; Hypoglycemia - genetics; Infant, Newborn; Insulin; Male; Medical sciences; Models, Chemical; Mutation; Pancreas; Peptides; Phenotype; Physiological aspects; Plasma; Protein Structure, Tertiary; Recombinant Fusion Proteins - genetics; Regulation; Tumors. Hypoglycemia; Type 2 diabetes; Endocrinopathy; Enzyme; Transferases; Diabetes mellitus; Glucokinase; Metabolic diseases; Genetics; Mutation; Hypoglycemia
• ISSN: 0012-1797; 1939-327X
• DOI: 10.2337/diabetes.52.9.2433

Insights Into the Biochemical and Genetic Basis of Glucokinase Activation From Naturally Occurring Hypoglycemia Mutations Anna L. Gloyn 1 , Kees Noordam 2 , Michèl A.A.P. Willemsen 3 , Sian Ellard 1 , Wayne W.K. Lam 4 , Ian W. Campbell 5 , Paula Midgley 6 , Chyio Shiota 7 , Carol Buettger 8 , Mark A. Magnuson 7 , Franz M. Matschinsky 8 and Andrew T. Hattersley 1 1 Department of Diabetes & Vascular Medicine, Peninsula Medical School, Exeter, U.K 2 Department of Paediatric Endocrinology, University Children’s Hospital, Nijmegen, the Netherlands 3 Department of Paediatric Neurology, University Medical Centre, Nijmegen, the Netherlands 4 Department of Clinical Genetics, Western General Hospital, Edinburgh, U.K 5 Department of Diabetes, Victoria Hospital, Kirkcaldy, U.K 6 Department of Neonatology, Royal Infirmary of Edinburgh, Edinburgh, U.K 7 Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 8 Department of Biochemistry and Biophysics and Diabetes Research Center, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania Address correspondence and reprint requests to Professor Andrew T. Hattersley, Diabetes and Vascular Medicine, Peninsula Medical School, Barrack Road, Exeter, EX2 5AX U.K. E-mail: a.t.hattersley{at}exeter.ac.uk Abstract Glucokinase (GCK) is a key regulatory enzyme in the pancreatic β-cell and catalyzes the rate-limiting step for β-cell glucose metabolism. We report two novel GCK mutations (T65I and W99R) that have arisen de novo in two families with familial hypoglycemia. Insulin levels, although inappropriately high for the degree of hypoglycemia, remain regulated by fluctuations in glycemia, and pancreatic histology was normal. These mutations are within the recently identified heterotropic allosteric activator site in the theoretical model of human β-cell glucokinase. Functional analysis of the purified recombinant glutathionyl S-transferase fusion proteins of T65I and W99R GCK revealed that the kinetic changes result in a relative increased activity index (a measure of the enzyme’s phosphorylating potential) of 9.81 and 6.36, respectively, compared with wild-type. The predicted thresholds for glucose-stimulated insulin release using mathematical modeling were 3.1 (T65I) and 2.8 (W99R) mmol/l, which were in line with the patients’ fasting glucose. In conclusion, we have identified two novel spontaneous GCK -activating mutations whose clinical phenotype clearly differs from mutations in ATP-sensitive K + channel genes. In vitro studies confirm the validity of structural and functional models of GCK and the putative allosteric activator site, which is a potential drug target for the treatment of type 2 diabetes. GCK, glucokinase GSIR, glucose-stimulated insulin release GST, glutathionyl S-transferase KATP, ATP-sensitive K+ MODY, maturity-onset diabetes of the young Footnotes Accepted June 3, 2003. Received April 8, 2003. DIABETES