Effect of Serum pH on StorageStabilityand ReactionLag Phaseof Human Creatine Kinaselsoenzymes
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چکیده
We report the effect of serum pH on the storage stability of the human creatine kinase isoenzymes and on the creatine kinase assay lag phase (Szasz et al., C/in. Chem. 22: 650, 1976). We also investigated the effect of including mercaptoethanol, N-acetyl-L-cysteine, monothioglycerol, ethylenediaminetetraacetate, or ethylene glycol bis(/3aminoethyl ether)-N,N,N#{231}N’-tetraacetate t 20, 4, and -20 #{176}C. Storage stability of the isoenzymes is profoundly affected by pH. For patients’ samples and semi-purified human creatine kinase isoenzymes added to heat-inactivated sera, increasing diluent pH above 7.0 decreases creatine kinase stability. The thiol agents or chelators generally give little or no protection above pH 7.5; at pH 8.5 they contribute significantly to isoenzyme instability. Storage at 4 #{176}C provides greater stability than storage at 20 #{176}C, particularly in the case of creatine kinase isoenzyme BB. The lag phase was minimum at a serum pH of 6.5, in the presence of 10 mmol of monothioglycerol per liter. Increasing serum pH to 8.5 prolongs the reaction lag phase by about 1 mm over the minimum. We recommend that, before they are stored at 4 #{176}C, the pH of patients’ samples be adjusted to 6.5 and oxidation of SH-groups be minimized by adding monothioglycerol to the sample.
منابع مشابه
Activation of human creatine kinase isoenzymes by pH and various sulfhydryl and chelating agents.
We report the effect of serum pH and of the presence or absence of mercaptoethanol, N-acetyl-L-cysteine, monothioglycerol, ethylenediaminetetraacetate, and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetate on the activation of the human creatine kinase isoenzymes. At the serum pH giving maximal enzyme stability and minimal assay lag phase (Nealon et al., Clin. Chem. 26: 1165-116...
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