Hexokinase phosphoryl group transfer kinases

This reaction, which is irreversible under intracellular conditions, is catalyzed by hexokinase. Recall that kinases are enzymes that catalyze the transfer of the terminal phosphoryl group from ATP to an acceptor nucleophile (see Fig. 13-10). Kinases are a subclass of transferases (see Table 6-3). The acceptor in the case of hexokinase is a hexose, normally D-glucose, although hexokinase also catalyzes the phosphorylation of other common hexoses, such as D-fructose and D-mannose. 

The stereochemical consequence of [lsO]thiophosphoryl and [l60, nO, lsO]phos-phoryl group transfer catalyzed by seven phosphotransferases were simultaneously determined in the author s laboratory and in the laboratory of J.R. Knowles. The first to be completed was the demonstration of inversion by adenylate kinase however, prior to that glycerokinase, hexokinase and pyruvate kinase had been shown to catalyze [l80]thiophosphoryl group transfer with the same stereochemical consequences, either all with inversion or all with retention. Glycerokinase was later shown to catalyze both [l60, nO, l80]phosphoryl and [l80]thiophosphoryl group... 

Phosphoryl transfer is a fundamental reaction in biochemistry and is one that was discussed in mechanistic and structural detail earlier (Section 9.4). Kinases are enzymes that catalyze the transfer of a phosphoryl group from ATP to an acceptor. Hexokinase, then, catalyzes the transfer of a phosphoryl group from ATP to a variety of six-carbon sugars (hexoses), such as glucose and mannose. Hexokinase, like adenylate kinase (Section 9.4.2) and all other kinases,... 

The enzyme name can tell us a lot about the reaction (see Section 20.1). The suffix -kinase tells us that the enzyme is a transferase that will transfer a phosphoryl group, in this case from an ATP molecule to the substrate. The prefix hexo- gives us a hint that the substrate is a six-carbon sugar. Hexokinase predominantly phosphorylates the six-carbon sugar glucose. 

Kinases Direct transfer of terminal phosphoryl group of ATP to substrate Creatine kinase Adenylate kinase Hexokinase Phosphoglycerate kinase Pyruvate kinase Protein kinase Myokinase Phosphofructokinase Type 1 (M-S-E) Type 1 Typel Type 1 Type 2 (S-M-E)... 

KInatM enzymes which catalyse the transfer of a phosphate residue (strictly speaking a phosphoryl group is transferred) from ATP to another substrate, in particular to the alcoholic hydroxyl groups of monosaccharides. Some important K. are hexokinase, which phosphorylates several hexoses at the C6 position, glucokinase, which is responsible for glucose 6-phosphate formation in the liver, and phosphofructo-kinase. 

Transferases Kinases Acyltransferases Transaldolases Methyl transferases Transfer of functional groups form one molecule to another. Example Phosphorylation of glucose by hexokinase A-B+C A+B-C... 

Kinases are enzymes that transfer a phosphate group from adenosine triphosphate (ATP), or other trinucleotide, to a number of biological substrates, such as sugars or proteins. They are part of a larger family of enzymes known as group transferases, but are limited to phosphate transfers. A typical reaction catalyzed by a kinase (e.g., hexokinase) is the phosphorylation of glucose upon its entry into a cell... 

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