| Enzyme inhibitor | This phosphagen (FW = 211.11 g/mol; CAS 67-07-2; 922-32-7 for disodium salt), known almost as commonly as creatine phosphate, is the primary cytosolic phosphoryl donor for the resynthesis of MgATP from MgADP through the action of creatine kinase in vertebrates and some invertebrates. While abundant in skeletal and cardiac muscle (40-60 mM), nonmuscle cells contain 3-5 mM, and some fungi (e.g., Candida) have intermediate levels of this metabolite. Note: The reported inhibitory action by creatine kinase is often due to impurities (e.g., the inhibition of 5’- nucleotidase is due to an impurity in the commercial phosphocreatine). The reported inhibition of AMP deaminase is due mainly to the presence of pyrophosphate. Phosphocreatine is a hygroscopic solid and very soluble in water. Unstable in acid, all is hydrolyzed after one minute at 100°C in 1.0 M HCl, and half is hydrolyzed in 4 min at 25°C in 0.5 M HCl. Molybdate and certain buffers reportedly accelerate hydrolysis. Hydrolysis is slow under slightly alkaline conditions (e.g., pH 7.8). Nevertheless, solutions should always be freshly prepared and stored frozen. Target(s): adenylate cyclase; AMP deaminase; glutamine synthetase; H+-extrusion by plasma membrane ATPase; NADH peroxidase; phosphofructokinase; and thiamin-phosphate diphosphorylase. |
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