Creatine phosphate. See

Uric acid is the end product of the purine metabolism. When uric acid excretion via the kidneys is disturbed, gout can develop (see p. 190). Creatinine is derived from the muscle metabolism, where it arises spontaneously and irreversibly by cyclization of creatine and creatine phosphate (see p. 336). Since the amount of creatinine an individual excretes per day is constant (it is directly proportional to muscle mass), creatinine as an endogenous substance can be used to measure the glomerular filtration rate. The amount of amino acids excreted in free form is strongly dependent on the diet and on the ef ciency of liver function. Amino acid derivatives are also found in the urine (e.g., hippu-rate, a detoxification product of benzoic acid). 

Muscle-specific auxiliary reactions for ATP synthesis exist in order to provide additional ATP in case of emergency. Creatine phosphate (see B) acts as a buffer for the ATP level. Another ATP-supplying reaction is catalyzed by adenylate kinase [1] (see also p.72). This disproportionates two molecules of ADP into ATP and AMP. The AMP is deaminated into IMP in a subsequent reaction [2] in order to shift the balance of the reversible reaction [1 ] in the direction of ATP formation. 

Crazy edge see PCP (phencyclidine) Creatine monohydrate see Creatine Creatine phosphate see Creatine Creeper see Heroin Creo-Terpin see Dextromethorphan... 

The high-energy compound steadily depleted during muscular activity is creatine phosphate (see here). Because the equilibrium for this reaction lies well to the right, virtually all of the muscle adenylate is maintained in the ATP form, rather than as ADP or AMP, as long as creatine phosphate is available. Thus, the energy source in red muscle is creatine phosphate, which regenerates ATP continually as it is depleted by muscle contraction. 

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. 

Biosynthesis of ATP. ATP is the irrunediate product of all cellular processes leading to the chemical storage of energy. It is biosynthesized by phosphorylation of ADP in the course of Substrate phosphorylation (see). Oxidative phosphorylation (see) and non-cyclic Photophosphorylation (see) in plants. Energy in the form of a third phosphate may also be transferred to ADP from other high-energy phosphates, such as creatine phosphate (see Creatine) or other nucleoside triphosphates, or in the adenylate kinase reaction. 

CPM, D-00322 Creatine phosphate, see P-00214 m-Cresol-6-aldehyde, see H-00276 / -Cresol-2-aldehyde, see H-00277... 

Sodium creatine phosphate (4H2O) [922-32-7] M 327.1. See creatine phosphate di-Na salt on p. 523 in Chapter 6. 

Figure 31-3. Arginine, ornithine, and proline metabolism. Reactions with solid arrows all occur in mammalian tissues. Putrescine and spermine synthesis occurs in both mammals and bacteria. Arginine phosphate of invertebrate muscle functions as a phosphagen analogous to creatine phosphate of mammalian muscle (see Figure 31-6).

In resting muscle, creatine phosphate forms due to the high level of ATP. If there is a risk of a severe drop in the ATP level during contraction, the level can be maintained for a short time by synthesis of ATP from creatine phosphate and ADP. In a nonenzymatic reaction [6], small amounts of creatine and creatine phosphate cyclize constantly to form creatinine, which can no longer be phosphorylated and is therefore excreted with the urine (see p. 324). 

An example of a random type of reaction is creatine + ATP creatine phosphate + ADP, which is catalyzed by creatine kinase (see Chapter 20). In this case, creatine and ATP are bound to the active site in either sequence, and after the transfer of the phosphate group of the bound ATP to the bound creatine both products are released in either sequence. 

A patient is severely acidotic and experiences serious muscle weakness. Her mitochondrial cytochrome b content is 0.1 nmol/mg protein (normal is 0.63), her creatine phosphate is low, and neither NADH nor succinate can reduce cytochrome c. The most likely problem is (see Nutr Rev 46 157-163, 1988)... 

S-30 fraction from wheat germ—commercial (Fisher catalog L-4440) or freshly prepared (see Appendix) supplemented with 125 mM ATP (potassium salt), 2.5 mM GTP (potassium salt), 100 mM creatine phosphate, and 0.5 mg/ml creatine Reaction buffer (300 mM HEPES, 30 mM dithiothreitol [pH 7.1])... 

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 phosphate shuttle, 202 Creatinine, 202-205 Cretinism, 737 Croltn s disease, 152 Ctoss-sectional studies, 963 Ctyploxanihinc, 554 C rypts, anatomy, 117-118 Cr, -see Computed tomcigraphy CTP, see Cyridine triphosphate Curds, 424... 

Creatine synthesis. The synthesis of creatine, including the major control, is depicted above. The tissue where the reaction occurs is indicated in parenthesis in purple. The formation of creatinine from creatine phosphate is also shown. (See text for more detail.)... 

See also Table 5.1, Genetic Code, Urea, Ornithine, Citrulline, Glycine, Creatine, Creatine Phosphate, Metabolism of Ornithine and Arginine, Essential Amino Acids... 

The latter reaction is strongly endergonic as written. However, the level of ATP is very high in mitochondria, so the reaction proceeds to the right. Creatine phosphate then diffuses from mitochondria to the myofibrils (see here), where it provides the energy for muscle contraction. 

See also The Structure of Muscle, The Sliding Filament Model, Creatine Phosphate... 

Muscle has an additional energy reserve in creatine phosphate, which generates ATP without the need for metabolizing fuels (see here). This reserve is exhausted early in a period of exertion and must be replenished, along with glycogen stores, as muscle rests after prolonged exertion. 

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