Phosphate phosphokinases

Fig. 4. Requirements, substrates, and products of Mo-nitrogenase catalysis, where I is the MoFe protein II the Fe protein and Pi is inorganic phosphate. The generating system is composed of creatine phosphate and creatine phosphokinase to recycle the inhibitory MgADP produced during catalysis to...

In the preceding sections the conversion of purines and purine nucleosides to purine nucleoside monophosphates has been discussed. The monophosphates of adenosine and guanosine must be converted to their di- and triphosphates for polymerization to RNA, for reduction to 2 -deoxyribonucleoside diphosphates, and for the many other reactions in which they take part. Adenosine triphosphate is produced by oxidative phosphorylation and by transfer of phosphate from 1,3-diphosphoglycerate and phosphopyruvate to adenosine diphosphate. A series of transphosphorylations distributes phosphate from adenosine triphosphate to all of the other nucleotides. Two classes of enzymes, termed nucleoside mono-phosphokinases and nucleoside diphosphokinases, catalyse the formation of the nucleoside di- and triphosphates by the transfer of the terminal phosphoryl group from adenosine triphosphate. Muscle adenylate kinase (myokinase)... 

S ATP -I- [DNA-directed eukaryotic RNA polymerase II subunit Ila] (<4> distinct from other protein phosphokinases, transfers about 20 phosphates to the heptapeptide repeats Pro-Thr-Ser-Pro-Ser-Tyr-Ser in C-terminal domain of MW 220000 subunit of RNA-polymerase II [7] <4> substrates are RNA-polymerase II subunits of wheat germ, soy bean, pea and human [7] phosphorylates predominantly Ser-residues [1-3,5,7] <1> kinase CTDKl almost exclusively phosphorylates Ser-residues [5] <1> kinase CTDK2 phosphorylates to a lesser extent Thr-resi-dues [1] <3-5> phosphorylates to a lesser extent Thr-residues [1,5,7] <1> phosphorylates Ser- and Thr-residues equally [6] <1,3,5> phosphorylates not Tyr-residues [1,6] <1> kinase CTDKl 33 mol phosphate per mol IIA-subunit [5] <1> kinase CTDK2 40-50 mol phosphate per mol IIA-subunit, i.e. 1 phosphate per heptapeptide repeat [5] <4> no substrate is GTP [7] <2,4> no substrates are CTP and UTP [3,7] <2> no substrates are dTTP and AMP-PNP [3] <4> no substrates are bovine serum albumin and calf thymus histone [7] <5> no substrate is phosvitin... 

Davis, R.H. Carbamyl phosphate synthesis in Neurospora crassa. I. Preliminary characterization of arginine-specific carbamyl phosphokinase. Biochim. Biophys. Acta, 107, 44-53 (1965)... 

PRPP is synthesized from ribose 5-phosphate derived from the pentose phosphate pathway (see Fig. 14-21), in a reaction catalyzed by ribose phosphate pyro-phosphokinase ... 

Chiral [160,170,180] Phosphate Monoesters for Determining the Stereochemical Course of Phosphokinases... 

In order to solve this mechanistic problem, a method for analysing the stereochemical course of phosphokinases has been developed using chiralf160,170,180]phosphate esters. Stereochemical analysis should allow a clear mechanistic distinction to be made, since inversion of configuration at phosphorus implies a direct in-line phosphoryl transfer mechanism whereas retention of configuration suggests a doubledisplacement mechanism with a phosphoryl-enzyme intermediate on the reaction pathway. 

Type II muscle fibers (white muscle, fast muscle) (Table 6) contribute to rapid muscle contraction by using energy obtained from stored ATP, and ATP production from creatine phosphate and anaerobic glycolysis of glycogen. However, the myoglobin content of these fibers is low [144,145], which may lead to less marked increases in serum myoglobin and creatine phosphokinase (CPK) in patients with ALPE. 

The simplest mechanism for generating ATP is phosphagen mobilization. In vertebrate tissues such as muscle containing creatine phosphate (PCr) this mobilization is catalyzed by creatine phosphokinase (CPK), a process which requires no 02 and can be written as follows ... 

Using LTC4 as substrate, nitrocellulose filters (0.2 pm pore size, 25-mm diameter) are soaked in incubation buffer (0.25 mM sucrose, 10 mM Tris-HCl, pH 7.4). A rapid filtration apparatus from Millipore (Bedford, MA) is prepared. A final volume of 110 pi of transport assay mixture (4 mM ATP (potassium salt), 10 mM creatine phosphate (Tris salt), 10 mM MgCl2, 10 mM Tris/HCl (pH 7.4), 5 mM glutathione (reduced), 0.25 mM sucrose, 100 pg/ml creatine phosphokinase (2 units/110 pi), 50 nM 3H-LTC4 (50 nCi/110 pi) pH 7.4) is preincubated at 37 °C for 1 min. Blanks are prepared by replacing ATP by 5 -AMP. 

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. 

ATP phosphorylates creatine to form creatine phosphate in a reaction catalyzed by creatine kinase (also known as creatine phosphokinase). 

The three tissue enzymes known to participate in formation of the phosphate esters are (1) thiaminokinase (a pyro-phosphokinase), which catalyzes formation of TPP and adenosine monophosphate (AMP) from thiamine and adenosine triphosphate (ATP) (2) TPP-ATP phosphoryl-transferase (cytosoHc 5"-adenylic kinase)which forms the triphosphate and adenosine diphosphate from TPP and ATP and (3) thiamine triphosphatase, which hydrolyzes TPP to the monophosphate. Although thiaminokinase is widespread, the phosphoryl transferase and membrane-associated triphosphatase are mainly in nervous tissue. 

Blood creatine phosphokinase (CPK) - increased Blood creatinine - increased Blood phosphate - decreased Blood potassium - decreased Blood urea nitrogen - increased... 

Creatine phosphokinase. The formation of creatine phosphate and its use to reform ATP is shown above. 

Creatine phosphate Creatine phosphokinase Creatinine Cyanide... 

Fig. 47.6. The creatine phosphokinase reaction. The high-energy bond is the unusual nitrogen-phosphate bond, as indicated by the blue squiggle.

The creatine formed is released from the liver and travels throngh the bloodstream to other tissues, particularly skeletal muscle, heart, and brain, where it reacts with ATP to form the high-energy compound creatine phosphate (see Fig. 47.6). This reaction, catalyzed by creatine phosphokinase (CK, also abbreviated as CPK), is reversible. Therefore, cells can use creatine phosphate to regenerate ATP. 

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