应 用 | Molecular Weight: ~81,000 Creatine Phosphokinase is a dimer composed predominantly of the skeletal muscle derived homodimer (MM). CK also exists as a heterodimer (MB) particularly in the myocardium. CK derived from brain tissue consists mainly of the brain source homodimer (BB). The amino acid sequences of the M chain and B chains are about 80% homologous. From the sequence, the molecular weight of the M chain is 43,112. E1%(280)= 8.76 pH Optimum: pH 8.8-9.0 for the forward reaction and pH 6.0-7.0 for the reverse reaction. CK is a cellular enzyme with a wide tissue distribution. Its physiological role is associated with ATP generation for contractile or transport systems. Increased levels of CK are associated with myocardial infarction, muscular dystrophy, hyperthyroidism, pulmonary infarction and cerebrovascular disease. Variations in relative isozyme distribution can provide additional information in the diagnosis of these conditions. Substrates:
Creatine, N-ethylglycocyamine and glyocyamine have been shown to act as substrates for CK.CK is very specific for ATP/ADP. Inhibitors: ADP is a
strong inhibitor of the forward reaction competing with ATP. Divalent cations such as Ca2+ (Ki=4.5 mM), Zn2+ and Cu2+ inhibit CK by competing with Mg2+.Other inhibitors include acetate, acetylsalicylic acid, adenosine, p-aminosalicylic acid, AMP, benzoic acid, bicarbonate, bromide, chloride, p-Chloromercuribenzoic acid, ethylene oxide, 2,4-fluorodinitrobenzene, iodide, malonic acid, NAD, nitrate, phosphate, pyrophosphate, salicylic acid, sulfate, sulfite, thyroxine, trichloroacetate, L-triiodothyroxine, L-triiodothyronine, and tripolyphosphate. The enzyme from Sigma has been used in the measurement of phosphocreatine in hippocampal neurons isolated from rat brains. |
