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A novel binding of GTP stabilizes the structure and modulates the activities of human phosphoglucose isomerase/autocrine motility factor
Authors:Hua-Yang Lin  Jyung-Hurng Liu  Ka-Lik Cheng  Jia-Yun Lin  Ni-Rung Liu  Menghsiao Meng
Affiliation:1. Graduate Institute of Biotechnology, National Chung Hsing University (NCHU), 250 Kuo-Kuang Road, Taichung, Taiwan 40227;2. Graduate Institute of Genomics and Bioinformatics, NCHU, Taichung, Taiwan 40227;3. Agricultural Biotechnology Center (ABC), NCHU, Taichung, Taiwan 40227;4. Rong Hsing Research Center for Translational Medicine, NCHU, Taichung, Taiwan 40227
Abstract:Phosphoglucose isomerase (PGI) catalyzes the interconversion between glucose 6-phosphate and fructose 6-phosphate in the glycolysis pathway. In mammals, the enzyme is also identical to the extracellular proteins neuroleukin, tumor-secreted autocrine motility factor (AMF) and differentiation and maturation mediator for myeloid leukemia. Hereditary deficiency of the enzyme causes non-spherocytic hemolytic anemia in human. In the present study, a novel interaction between GTP and human PGI was corroborated by UV-induced crosslinking, affinity purification and kinetic study. GTP not only inhibits the isomerization activity but also compromises the AMF function of the enzyme. Kinetic studies, including the Yonetani-Theorell method, suggest that GTP is a competitive inhibitor with a Ki value of 63 μM and the GTP-binding site partially overlaps with the catalytic site. In addition, GTP stabilizes the structure of human PGI against heat- and detergent-induced denaturation. Molecular modelling and dynamic simulation suggest that GTP is bound in a syn-conformation with the γ-phosphate group located near the phosphate-binding loop and the ribose moiety positioned away from the active-site residues.
Keywords:Phosphoglucose isomerase  Glucose-6-phosphate isomerase  Autocrine motility factor  GTP  Inhibition kinetics
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