Transphosphorylases

Finally, one should recognize that determinations of the critical concentration depend wholly on the validity of the equilibrium or steady-state assumptions. If a stable end point for prdtomer-polymer coexistence is not attained, then kinetic factors affect the observed behavior. With the well recognized tendency of tubulin to lose its ability to engage in assembly reactions upon storage even at low temperature, and with the presence of various nucleotide hydrolases and transphosphorylases in microtubule protein, such kinetic effects are a serious problem. 

Kiaira, J.K. Njogu, R.M. Evidence for glycerol 3-phosphate glucose transphosphorylase activity in bloodstream Trypanosoma brucei brucei. Int. J. Biochem., 21, 839-845 (1989)... 

Keutel, H.J. Okabe, K. Jacobs, H.K. Ziter, R Maland, L. Kuby, S.A. Studies on adenosine triphosphate transphosphorylases. XL Isolation of the crystalline adenosine triphosphate-creatine transphosphorylases from the muscle and brain of man, calf, and rabbit and a preparation of their enzymatically active hybrids. Arch. Biochem. Biophys., 150, 648-678 (1972)... 

Kuby, S.A. Fleming, G. Frischat, A. Cress, M.C. Hamada, M. Studies on adenosine triphosphate transphosphorylases. Human isoenzymes of adenylate kinase isolation and physicochemical comparison of the crystalline human ATP-AMP transphosphorylases from muscle and liver. J. Biol. Chem., 258, 1901-1907 (1983)... 

Ratliff, R.L. Weaver, R.H. Lardy, H.A. Kuby, S.A. Nucleoside-triphosphate-nucleoside diphosphate transphosphorylase (nucleoside diphosphokinase). 1.Isolation of the crystalline enzyme from brewerseast. J. Biol. Chem., 239, 301-309 (1964)... 

Albrecht, G.J. Purification and properties of nucleoside triphosphate-adenosine monophosphate transphosphorylase from beef heart mitochondria. Biochemistry, 9, 2462-2470 (1970)... 

In 1940 carbonic anhydrase was shown to be a zinc enzyme, and in 1955 carboxypeptidase became the second recognized zinc enzyme. Since then more than 300 other zinc enzymes have been reported, and functionally they are of many kinds, including alcohol dehydrogenases, aldolases, peptidases, carboxypeptidases, proteases, phosphatases, transphosphorylases, a transcarbamylase, and DNA- and RNA-polymerases. 

Jl. Jacobs, H., Okabe, K., Yue, R., Keutel, H., Ziter, F., Palmieri, R., Tyler, F., and Kuby, S. A., A comparison of normal human ATP-creatine transphosphorylases with those from progressive muscular dystrophy tissues. Fed. Proc. Fed. Amer. Soc. Exp. Biol. 28, 346 (1969). 

PgcM <4> (<4> bifunctional PgcM with j5-phosphoglucomutase, EC 5.4.2.1, and glucose 1-phosphate phosphodismutase activities [3]) [3] glucose 1-phosphate transphosphorylase phosphodismutase... 

Smith, R.A. Theisen, M.C. Phosphoramidate-hexose transphosphorylase. Methods EnzymoL, 9, 403-407 (1966)... 

Glucose-l-phosphate transphosphorylase uses glucose-l-phosphate as the phosphate donor as well as the acceptor. 

When the transferase systems (transphosphorylases, transglycosidases, transpeptidases, transmethylases, transacylases, etc.) which function inside the cell, cease to act and compete with the transfer to water, the hydrolases take over and cause a certain amount of hydrolysis of the cellular contents. 

Hexokinase transfers a phosphate group from ATP to glucose with the formation of glucose-6-phosphate, and fructohexokinase performs the same transfer to fructose forming fructose-l-phosphate. The transphosphorylases can be divided into several types according to the magnitude of JF for the transfer reaction. 

Among the transphosphorylase systems in which energy-rich bonds are involved and the —AF is small (so that the reaction is readily reversible) we may list the following ... 

The enzymatic transfer of a phosphate from one compound to another through the mediation of the adenylpyrophosphates is well known. Enzymes which catalyze the equilibrium between ATP and high-energy compounds are known as transphosphorylases. A more systematic nomenclature is that of Dixon,who calls a phosphokinase any enzyme that catalyzes the transfer of a phosphate from ATP. This would include the hexokinases as well as the transphosphorylases. 

Adenosine-5 -phosphate (AMP) can be estimated by converting all of the ATP, ADP, and AMP into ATP with creatine adenylic transphosphorylase (10) and excess creatine phosphate (Fig. 3). From the total ATP thus obtained the amount of AMP can be calculated by difference. 

In order to determine phosphocreatine another aliquot of the extract is treated with excess AMP plus creatine adenylic transphosphorylase. The initial ATP is subtracted from this reading and the difference is compared to a determination made with an internal standard (see Fig. 4). 

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