Phosphotransferases adenosine kinase

Reactions (35a) and (35b) are catalyzed by galactose-1-P uridylyltransferase and UDPglucose pyrophosphorylase, respectively reactions (36a) and (36b) are catalyzed by nucleoside diphosphate kinase and adenylate kinase, respectively and reactions (37a) and (37b) are catalyzed by nucleoside phosphotransferase and adenosine kinase, respectively. 

Phosphoribosyltransferase activity was found for hypoxanthine, guanine and xanthine but not for adenine (2). Adenine and guanine deaminase activities are present. Phosphorylase activities were found for adenosine, guanosine and inosine. Also present were adenosine kinase and a guanosine phosphotransferase neither inosine kinase nor phosphotransferase activity was present. The IMP dehydrogenase differs from the mammalian enzyme in that it does not require for activity and it is more sensitive to inhibition by mycophenolic acid (13). 

There is a relatively high activity of adenosine phosphorylase and low levels of adenosine kinase, deaminase and phosphotransferase (66). The adenosine kinase is responsible for incorporation of adenosine analogs such as tubercidin (67). 

A number of reactions which consume ATP generate AMP rather than ADP as a product, only few produce adenosine [534]. ATP may be recycled from AMP using polyphosphate-AMP phosphotransferase and polyphosphate kinase in a tandem-process at the expense of inorganic polyphosphate as phosphate donor for both steps. Alternatively, the combination of adenosine kinase and adenylate kinase were used (Scheme 2.80) [535]. 

Selected entries from Methods in Enzymology [vol, page(s)] Adenylate kinase contamination in in phosphotransferases, 63, 7 as contaminant enzyme preparations, 64, 24 P, P -di(adenosine-5 )-tetraphosphate and P, P -di(adenosine-5 )-pentaphosphate inhibition of adenylate kinase, 63, 7, 401, 483. 

AMP NADH Disappearance Adenylate Kinase Adenosine Phosphotransferase, GMP Synthetase ... 

In a number of cases there may be a contaminating enzyme present which acts on one or more of the substrates, products, or effectors of the system under study. It may be necessary to include in the reaction mixture a specific inhibitor for that contaminating activity. For example, adenylate kinase is often present in preparations of a number of phosphotransferases. It is often advantageous, in such instances, to include a specific inhibitor of adenylate kinase (e.g., P, P -di(adenosine-5 )-tetraphosphate or P P -di(adenosine-5 )-pentapho-sphate). If an inhibitor of the contaminating activity is added as an additional constituent of the reaction mixture, the investigator should demonstrate that the inhibitor is not an effector of the enzyme under study. 

Beyond the effect of magnesium ion concentration on the equilibrium hydrolysis of adenosine triphosphate to adenosine diphosphate , there is ample evidence that MgATP is generally the most widespread substrate in kinase-type phosphotransferase reactions as well as other ATP-dependent processes. The extent to which MgATP is formed in solution depends on the free (or uncomplexed) magnesium ion concentration, as shown by the following equilibrium constant ... 

Falke, D. Labenz, J. Brauer, D. Muller, W.E.G. Adenosine diphosphate thymidine 5-phosphotransferase, a new enzyme activity, associated with the Herpes simplex virus-induced deoxypyrimidine kinase. Biochim. Biophys. Acta, 708, 99-103 (1982)... 

Hamada, M. Sumida, M. Okuda, H. Watanabe, T. Nojima, M. Kuby, S.A. Adenosine triphosphate-adenosine-5-monophosphate phosphotransferase from normal human liver mitochondria. Isolation, chemical properties, and immunochemical comparison with Duchenne dystrophic serum aberrant adenylate kinase. J. Biol. Chem., 257, 13120-13128 (1982)... 

Creatine Kinase (Adenosine 5 -Triphosphate-Creatine Phosphotransferase)... 

Adenosine triphosphate creatine A-phosphotransferase (EC 2.7.3.2), also creatine phosphokinase. Creatine kinase is found in muscle and is responsible for the formation of creatine phosphate from creatine and adenosine triphosphate creatine phosphate is a higher energy source for muscle contraction. Creatine kinase is elevated in all forms of muscular dystrophy. Creatine kinase is dimer and is present as isozymes (CK-1, BB CK-2, MB CK-3, MM) and Ck-mt (mitochondrial). Creatine kinase is also used to measure cardiac muscle damage in myocardial infarction. See Bais, R. and Edwards, J.B., Creatine kinase, CRC Crit. Rev. Clin. Lab. ScL 16, 291-355, 1982 McLeish, M.J. and Kenyon, G.L., Relating structure to mechanism in creatine kinase, Crit. Rev. Biochem. Mol. Biol 40, 1-20, 2005. 

Creatine kinase, CK (or creatine phosphotransferase, E.C. 2.7.3.2) is an important enzyme in our body involved in energy transfer in muscle. Specifically, the enzyme catalyzes phosphate transfer from creatine phosphate, CrP, to Mg -coordinated adenosine diphosphate, MgADP, to create adenosine triphosphate, ATP, according to the scheme in Fig. 10.3. 

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