Bacterial Glucokinase as an Enzymic Reagent of Good Stability for Measurement of Creatine Kinase Activity

抄録

An enzymic reagent, that has long-term stability even in the liquid state, was successfully employed for the measurement of serum creatine kinase (CK, EC 2.7.3.2) activity. The enzyme used was the thermostable glucokinase (GlcK, EC 2.7.1.2) obtained from the thermophile Bacillus stearothermophilus. The reagent was found to be stable in solution for about one month at 6°C and for about one week at 30°C. This substitution of glucokinase for the hexokinase of the most commonly used hexokinase-glucose-6-phosphate dehydrogenase (HK-G6PDH) method results in a remarkable improvement of the method. The CK activity measured by the GlcK-G6PDH method was linear up to about 2, 000U/liter at 37°C. The GlcK-G6PDH method was found to give a satisfactory precision and reproducibility (coefficient of variation less than 2.17%). Over a wide range of CK activity, an excellent agreement was obtained between the GlcK-G6PDH and the HK-G6PDH methods. Furthermore several coexistents and anticoagulants were found to have little effect on the measured value of CK activity by the GlcK-G6PDH method.