Hexokinases, protein binding

Feigner, P.L. and Wilson, J.E., Hexokinase binding to polypropylene test tubes. Artifactual activity losses from protein binding to disposable plastics. Anal. Biochem., 74,631,1976. 

Arabinose-binding protein domains 1 and 2 Dihydrofolate reductase Adenylate kinase Rhodanese domains 1 and 2 Glutathione reductase domains 1 and 2 Phosphoglycerate mutase Phosphoglycerate kinase domain 2 Pyruvate kinase domain 3 Hexokinase domains 1 and 2 Catalase domain 3 Aspartate aminotransferase... 

Schematic representation of the change in conformation of the hexokinase enzyme on binding substrate. E and E are the inactive and active conformations of the enzyme, respectively. G is the sugar substrate. Regions of protein or substrate surface excluded from contact with solvent are indicated by a crinkled line. Figure 8.3 presents a more detailed view of the hexokinase molecule. (Source From W. S. Bennett and T. A. Steitz, Glucose-induced conformational changes in yeast hexokinase, Proc. Natl. Acad. Sci. USA 75 4848, 1978.)...

Structural studies of the oxy-Cope catalytic antibody system reinforce the idea that conformational dynamics of both protein and substrate are intimately intertwined with enzyme catalysis, and consideration of these dynamics is essential for complete understanding of biologically catalyzed reactions. Indeed, recent single molecule kinetic studies of enzyme-catalyzed reactions also suggest that different conformations of proteins are associated with different catalytic rates (Xie and Lu, 1999). In addition, a number of enzymes are known to undergo conformational changes on binding of substrate (Koshland, 1987) that lead to enhanced catalysis two examples are hexokinase (Anderson and Steitz, 1975 Dela-Fuente and Sols, 1970) and triosephosphate isomerase (Knowles, 1991). 

Figure 34.16. Actin and Hexokinase. A comparison of actin (blue) and hexokinase from yeast (red) reveals structural similarities indicative of homology. Both proteins have a deep cleft in which nucleotides bind. 

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