Creatine kinase response surfaces explored by use of factorial experiments and simplex maximization.

Abstract

We conducted a five-component, five-level response-surface experiment to optimize the pH and the concentrations of magnesium, creatine phosphate, adenosine diphosphate, and buffer in an assay for creatine kinase. Under optimal conditions, creatine kinase activity was about 5% greater than that obtained with a previously reported assay (Clin Chem 23: 1569, 1977). We also applied a simplex maximization algorithm to the response-surface equation to locate areas of maximum sensitivity. Reaction conditions for two such areas were found, each yielding approximately 11% more activity than with the previously reported method.

International Federation of Clinical Chemistry (IFCC): Scientific Division, Committee on Enzymes. IFCC methods for the measurement of catalytic concentration of enzymes. Part 7. IFCC method for creatine kinase (ATP: creatine (N‐phosphotransferase, EC 2.7.3.2). IFCC Recommendation

“…Multivariate studies show that simultaneous increases of Mg 2+ to 15 mmol/1 and ADP to 3"5 mmol/1 increase CK reaction rates by 6-8% [25,30,31] (see Section 8). This change increases the ADP/AMP molar ratio from the current 0"4 to 0"7, and will increase residual adenylate kinase activity [9].…”

“…The investment in time and manpower required to validate a new method not only for accuracy but also for transferability, precision, and expected reference values, is substantial. The decision not to replace well-accepted conditions as described in this IFCC method [1-8] by slightly changed conditions [30,31] was therefore made by the Expert Panel on Enzymes. This decision was based on the above criteria and was carefully considered.…”

Response Surface Methodology

“…They used a complete second order model in the independent variables to graduate the response surface. The fitted model was explored by plotting contours of constant response and estimating the location of the stationary point Fast et al (1983). used a central composite design with five independent variables in an assay for creatine kinase.…”