Creatine kinase reaction

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 ... 

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 ... 

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

This muscle phosphotransferase (EC 2.132) catalyzes the reversible rephosphorylation of ADP to form ATP (/.c., T eq = [ATP][Creatine]/([Creatine phosphate] [ADP]) = 30). In resting muscle, creatine phosphate is synthesized at the expense of abundant stores of ATP intracellular creatine phosphate stores often reach 50-60 mM. If ATP is suddenly depleted by muscle contraction, its product ADP is immediately converted back into ATP by the reverse of the creatine kinase reaction. Depending on the pH at which the enzyme is studied, the kinetic reaction can be either rapid equilibrium random or rapid equilibrium ordered. A-Ethylglycocyamine can also act as a substrate. 

CREATINE KINASE. The creatine kinase reaction can be written as follows ... 

Xian R, Nascimben L, Kaddurah-Daouk R, et al. Depletion of energy reserve via the creatine kinase reaction during the evolution of heart failure in cardiomyo-pathic hamsters. J Mol Cell Cardiol. Apr 1996 28(4) 755-765. 

Exploration of Bulk Tolerance. Most affinity labels contain functional groups added to the substrate s basic structure. Discerning just where added bulk can be tolerated by the enzyme is therefore crucial information. In the case of creatine, it has been determined (92,93) that the structures below, for example, are good substitutes for creatine in the creatine-kinase reaction... 

Figure 4.. Possible structure of the transition state for phos-phoryl transfer in the creatine kinase reaction. Adapted from Cook et al(95).

M. Schar, A.-M. M. El-Sharkawy, R. G. Weiss and P. A. Bottomley, Triple repetition time saturation transfer (TRiST) P spectroscopy for measuring human creatine kinase reaction kinetics. Magn. Reson. Med., 2010, 63,1493-1501. 

Measurement of creatine kinase reaction rate in human brain using magnetization transfer image-selected in vivo spectroscopy (MT-ISIS) and a volume radiofre-... 

Buist, R. Kroeker, S. Peeling, J. Temperature dependence of the creatine kinase reaction measured in rat brain in vivo by 31P NMR saturation transfer. Can. J. Chem., 77, 1887-1891 (1999)... 

Gregor, M. Mejsnar, J. Janovska, A. Zurmanova, J. Benada, O. Mejsnaro-va, B. Creatine kinase reaction in skinned rat psoas muscle fibers and their myofibrils. Physiol.Res., 48, 27-35 (1999)... 

When a sudden demand for energy depletes ATP, the PCr reservoir is used to replenish ATP at a rate considerably faster than ATP can be synthesized by catabolic pathways. When the demand for energy slackens, ATP produced by catabolism is used to replenish the PCr reservoir by reversal of the creatine kinase reaction. Organisms in the lower phyla employ other PCr-like molecules (collectively called phosphagens) as phosphoryl reservoirs. 

The presence of a general acid/base catalyst at the creatine binding site, together with a recent measurement of a short (y 6 A) distance from Cr +ADP to the phosphorus of P-creatine (13), imply an associative mechanism for the creatine kinase reaction. 

Lawson, J.W.R. Veech, R.L. (1979). Effects of pH and free Mg2 on the Keq of the creatine kinase reaction and other phosphate hydrolyses and phosphate transfer reactions. J. Biol. Chem. 254, 6528-6537. 

Creatinine results from the irreversible, nonenzymatic dehydration and loss of phosphate from phosphocreatine (Fig. 1). Creatinine is used as an indicator of skeletal muscle mass because it is a by-product of the creatine kinase reaction and it is one of the most widely used clinical markers to assess renal function. Urine levels of creatinine are good indicators of the glomerular filtration rate of the kidneys (i.e., the amount of fluid filtered per unit time). 

Some phenomena of enzyme activation or inhibition are caused by interaction between the modifier and a nonenzy-matic component of the reaction system, such as the substrate (e.g., Mg combining with ATP to form MgATP, the required substrate for the creatine kinase reaction). In most cases, however, the modifier combines with the enzyme itself in a manner analogous to the combination of enzyme and substrate. 

During periods of physical inactivity, creatine phosphate is formed from creatine and ATP simply by reversal of the creatine kinase reaction. 

Perry SB, McAuliffe J, Balschi JA, Hickey PR, Ingwall JS (1988) Velocity of the creatine kinase reaction in the Neonatal rabbit heart role of mitochondrial creatine kinase. Biochemistry 27 2165-2172... 

In resting muscle phosphocreatine is present at at least five times the molar concentration of total adenine nucleotides and during contraction the creatine kinase reaction helps to maintain the intracellular concentration of ATP. 

Travers, F., Barman, T. E. Bertrand, R. (1979) Transient-phase studies on the creatine kinase reaction. European Journal of Biochemistry, 100, 149-55. 

Measure enzyme kinetics - saturation transfer for creatine kinase reaction Rb K congener. Measure K fluxes... 

The technique of saturation transfer has been used to measure in vivo the unidirectional rates of the ATPase and creatine kinase reactions, which will be discussed in later sections. In this technique, developed and first applied by Forsen and Hoffman (1963), the nuclear spin magnetization of one chemical species is perturbed from its equilibrium value and the appearance of nonequilibrium magnetization in a second, product, species is monitored to determine the reaction rate. The technique measures reaction rates in equilibrium or steady state conditions and has a time resolution of 1 s or less. Consider a second-order reaction ... 

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