Pyruvate phosphokinase

The rapid transfer of this energy-rich phosphate to ADP with formation of ATP is brought about by pyruvic phosphokinase. 

The phosphoenolpyruvic acid is the subject of the second transfer of phosphate, in the presence of pyruvic phosphokinase, a phosphokinase acting almost at equilibrium (low AF) the transfer is brought about with conservation of the energy-rich bond. 

The role of uridine triphosphate (UTP) in the hexokinase and pyruvate phosphokinase reaction is possibly indirect, since the addition of ADP markedly accelerates the reaction as discussed by Kalckar. < The following equilibrium appears likely UTP -I- ADP UDP + ATP... 

I n this way we have shown that phosphoryl transfer catalysed by Bacillus stearothermophilus and rabbit skeletal muscle phosphofructokinase (6), and rabbit skeletal muscle pyruvate kinase occurs with inversion of configuration at phosphorus (7). The simplest interpretation of these stereochemical results is that phosphoryl transfer occurs by an in-line mechanism in the enzyme substrate ternary complexes. Stereochemical analysis is thus proving to be of considerable importance for delineating the mechanism adopted by phosphokinases. ... 

Alteration of serum enzyme activity has been shown to be a sensitive parameter of tissue injury (20). While the activities of such enzymes as pyruvate kinase, lactate dehydrogenase, glutamate oxaloacetate transaminase, alkaline phosphatase, and creatine phosphokinase in rat serum were significantly altered by the deprivation of dietary vitamin E, the activities of these enzymes were not influenced by smoking exposure under the experimental conditions (Table I). 

The sensitivity of this method is directly related to the apparent molar enthalpy of reaction, so that very endo- or exothermic reactions will be most readily followed. Examples of the application of this method to the determination of enzyme kinetic parameters include dihydrofolate reductase, creatine phosphokinase, hexo-kinase, urease, trypsin, HIV-1 protease, heparinase, and pyruvate carboxylase. 

The in situ generation of GDP-Fuc from P-fucose-1-phosphate coupled with the transfer of the fucose moiety on to A -acetyllactosamine has also been probed on an analytical scale [96]. In the presence of GTP P-fucose-1-phosphate is converted to GDP-Fuc by GDP-fucose pyrophosphorylase. GDP-Fuc is then used by an a(l-3)fucosyl transferase to transfer the fucose moiety on to A -acetyllactosamine. The released GDP is recycled and phosphorylated to give GTP by a phosphokinase with phosphoenol pyruvate as phosphate source. The pyrophosphate produced in the complete cycle is decomposed by pyrophosphatase (see Scheme 16). 

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