Kinases creatine

Creatine kinase catalyzes the reversible reaction whereby ADP + phosphocre-atine form ATP + creatine. One HPLC method developed for this activity involved the direct determination of the ATP formed. 

The reaction mixture contained ADP, AMP, and KF (the last to inhibit any adenylate kinase activity), phosphocreatine, and magnesium, at concentrations 10-fold excess of ADP. The reaction was started by the addition of enzyme and terminated with a boiling water bath. 

Prepared creatine kinase was obtained from a commercial source. 

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The loss of NADH is followed for determination of the en2yme creatine kinase. 

Enzymes, measured in clinical laboratories, for which kits are available include y-glutamyl transferase (GGT), alanine transferase [9000-86-6] (ALT), aldolase, a-amylase [9000-90-2] aspartate aminotransferase [9000-97-9], creatine kinase and its isoenzymes, galactose-l-phosphate uridyl transferase, Hpase, malate dehydrogenase [9001 -64-3], 5 -nucleotidase, phosphohexose isomerase, and pymvate kinase [9001-59-6]. One example is the measurement of aspartate aminotransferase, where the reaction is followed by monitoring the loss of NADH ... 

A good example of an affinity label for creatine kinase has been presented (35). This enzyme catalyzes the reversible transfer of a phosphoryl group from adenosine triphosphate [56-65-5] (17) to creatine [57-00-1] (18), leading to adenosine diphosphate [7584-99-8] (19) and phosphocreatine [67-07-2]... 

A/-(2,3-Epoxypropyl)-A/-amidinoglycine [70363-44-9] (21) was shown to be an affinity label of creatine kinase. Its mechanism of covalent bond formation is outlined as follows ... 

Creatine Kinase Acts by a Random, Single-Displacement Mechanism... 

An example of a random, single-displacement mechanism is seen in the enzyme creatine kinase, a phosphoryl-transfer enzyme that uses ATP as a phosphoryl... 

ATP stores in muscle are augmented or supplemented by stores of phosphocreatine. During periods of contraction, phosphocre-atine is hydrolyzed to drive the synthesis of needed ATP in the creatine kinase reaction ... 

Muscle cells contain two different isozymes of creatine kinase, one in the mitochondria and one in the sarcoplasm. Explain. 

Mitochondria are surrounded by a simple outer membrane and a more complex inner membrane (Figure 21.1). The space between the inner and outer membranes is referred to as the intermembrane space. Several enzymes that utilize ATP (such as creatine kinase and adenylate kinase) are found in the intermembrane space. The smooth outer membrane is about 30 to 40% lipid and 60 to 70% protein, and has a relatively high concentration of phos-phatidylinositol. The outer membrane contains significant amounts of porin —a transmembrane protein, rich in /3-sheets, that forms large channels across the membrane, permitting free diffusion of molecules with molecular weights of about 10,000 or less. Apparently, the outer membrane functions mainly to... 

The effect of a statin is usually determined by measuring fasting plasma lipids and lipoproteins after 4-6 weeks of treatment. Liver enzymes and eventually creatine kinase (in case of myositis liver enzymes are usually also elevated) are measured simultaneously to exclude side effects related to liver and muscles. After the treatment goal has been reached, blood sampling is usually performed 1-2 times a year. 

In resting muscle the high concentration of ADP does not decrease the proton gradient effectively and the high membrane potential slows electron transport. ADP, formed when ATP is hydrolyzed by myosin ATPase during contraction, may stimulate electron transport. However, the concentration of ATP (largely as its Mg salt) is buffered by its readily reversible formation from creatine phosphate catalyzed in the intermembrane space, and in other cell compartments, by the various isoenzymes of creatine kinase (reviewed by Walliman et al., 1992). 

Wallimann, T., Wyss. M., Brdicza, D., Nicolay, K.. Eppenberger, H.M. (1992). Intracellular compartmentation. structure and function of creatine kinase isoenzymes in tissues with high and fluctuating energy demands The phosphocreatine circuit for cellular energy homeostasis. Biochem. J. 281,21-40. 

The middle panel shows the fall in PCr concentration in the muscle and the simultaneous increase in Pj released daring ATP degradation and resynthesis via the creatine kinase reaction ... 

The lower panel shows the decreasing concentration of ATP, to about 60% of resting levels, and the simultaneous equimolar increase in IMP. The fall in ATP started when most of the PCr store was utilized, resulting in a decreased rate of ADP phosphorylation via the creatine kinase reaction. The resultant accumulation of ADP stimulates adenylate kinase activity and subsequently IMP is formed via the AMP deaminase reaction ... 

It is generally accepted that the two main fiber types have different metabolic profiles with higher activities of Ca activated myosin ATPase, creatine kinase. 

Creatine supplementation has been shown to increase the rate of PCr resynthesis in the recovery period after ischemic exercise (Greenhaff et al., 1993a). This could be attributed to an acceleration of oxidative phosphorylation by increased free creatine content available to the mitochondrial fraction of the creatine kinase enzyme, as previously suggested (Bessman and Fonyo, 1966). 

Bessman, S.P. Fonyo, A. (1966). The possible role of mitochondrial bound creatine kinase in regulation of mitochondrial respiration. Biochem. Biophys. Res. Commun. 22, 597-602. 

Mehta, H.B., Popovich, B.K., Dillman, W.H. (1988). Ischemia induces changes in the level of mRNAs coding for stress protein 71 and creatin kinase M. Circ. Res. 63,512—517. 

In our laboratory, we have focused our attention on the syntheses of various analogs of creatine, 17, a substrate for the enzyme creatine kinase from rabbit muscle (2). The reaction catalyzed by this enzyme is... 

Some Kinetic Parameters for Analogs of Creatine in the Creatine Kinase Reaction (71)... 

Use of the plasma enzyme creatine kinase Mb (CK-MB) in the diagnosis of myocardial infarction. 

Creatine kinase Muscle disorders and myocardial infarction... 

Mitochondria have an outer membrane that is permeable to most metabohtes, an inner membrane that is selectively permeable, and a matrix within (Figure 12-1). The outer membrane is characterized by the presence of various enzymes, including acyl-CoA synthetase and glycerolphosphate acyltransferase. Adenylyl kinase and creatine kinase are found in the intermembrane space. The phospholipid cardiolipin is concentrated in the inner membrane together with the enzymes of the respiratory chain. 

Figure 12-14. The creatine phosphate shuttle of heart and skeletal muscle. The shuttle allows rapid transport of high-energy phosphate from the mitochondrial matrix into the cytosol. CKg, creatine kinase concerned with large requirements for ATP, eg, muscular contraction CIC, creatine kinase for maintaining equilibrium between creatine and creatine phosphate and ATP/ADP CKg, creatine kinase coupling glycolysis to creatine phosphate synthesis CK, , mitochondrial creatine kinase mediating creatine phosphate production from ATP formed in oxidative phosphorylation P, pore protein in outer mitochondrial membrane.

Creatine phosphate is formed from ATP and creatine (Figure 49-16) at times when the muscle is relaxed and demands for ATP are not so great. The enzyme catalyzing the phosphorylation of creatine is creatine kinase (CK), a muscle-specific enzyme with clinical utility in the detection of acute or chronic diseases of muscle. 

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