The Catalytic Activity and Activation Energy of Creatine Kinase Isoenzymes

Abstract

The catalytic activity and activation energy of an enzyme are obtained by measuring the rate of the enzymic reaction at two different temperatures. With the aid of the Arrhenius equation, these two parameters can be used to calculate a value proportional to the quantity of enzyme. Using this approach to investigate the isoenzymes of creatine kinase, it was shown that the activation energy increased in the order creatine kinase MM, MB, BB. Mixtures of the isoenzymes showed an apparent mean activation energy, which likewise could be determined using the Arrhenius equation.Ageing of the isoenzymes results in an exponential decrease of catalytic activity, accompanied by a continuous increase in activation energy, the calculated quantity of enzyme remaining constant. Inactivation is therefore not an all-or-nothing process; rather a stepwise inactivation of individual molecules must be assutiied. The results of these ageing experiments and observations by other authors suggest that a similar inactivation occurs in vivo. Die kataly tische Aktivität und Aktivierungsenergie der Kreatinkinase-IsoenzymeZusammenfassung: Durch die Messung der Geschwindigkeit einer enzymatischen Reaktion bei zwei verschiedenen Temperaturen erhält man die kataly tische Aktivität und die Aktivierungsenergie des Enzyms. Aus beiden läßt sich gemäß der Arrhenius*Gleich\mg eine der Enzymmenge proportionale Größe berechnen. Mit dieser Methode untersuchten wir die Isoenzyme der Kreatinkinase und stellten fest, daß die Aktivierungsenergie in der Reihenfolge Kreatinkinase MM, MB und BB ansteigt. Mischungen der Isoenzyme zeigen eine scheinbare, mittlere Aktivierungsenergie, die sich ebenfalls mit der Arrhemus-Gleichung bestimmen läßt.Bei der Alterung der Isoenzyme in vitro fällt die kataly tische Aktivität exporientiell ab. Daran gekoppelt ist eine kontinuierliche Zunahme der Aktivierungsenergie, die errechnete Enzymmenge bleibt dabei konstant. Die Inaktiviefung verläuft demnach nicht nach dem Alles-oder-Niehts Prinzip, vielmehr muß eine stufenweise Inaktivierung der einzelnen Moleküle angenommen werden. Die Ergebnisse dieser Alterungsversuche, sowie Beobachtungen anderer Autoren lasseh vermuten, daß auch in vivo eine vergleichbare Inaktivierung stattfindet. l ) Nonstandard abbreviations: CK: creatine kinase (ATP: creatine-phosphotransferase, EC 2.7.3.2). Greatine kinase MM, MB and BB: creatine kinase isoenzymes from striated muscle, heart and brain, respectively.

Indices for the age of the creatine kinase M-chain in the blood

“…This is also in agreement with Fig. 3 and with our recently published data on the gradual changes in apparent activation energy of CK in the human blood circulation [21]. In addition, individual u values for CK isozymes [lo], CK variants [22] and some other isoenzyme systems [23,24] have already been described.…”

A novel arginine kinase from the shrimp Neocaridina denticulata: The fourth arginine kinase gene lineage

“…We found that the reported E a values for the reactions of Limulus AK (54.4 kJ/mol) and rabbit CK (49.4 kJ/mol for MM-isoform and 62.8 kJ/mol for BB-isoform (Hagelauer and Faust, 1982)) were different from those of Neocaridina AKs (Table 4). Here, it is important to note that the thermodynamics of activation only provide information leading to the rate-limiting step.…”

Insights into the Phosphoryl Transfer Mechanism of Human Ubiquitous Mitochondrial Creatine Kinase

“…The bond lengths indicate that uMtCK may follow a dissociative catalytic mechanism. This dissociative characteristic of TS2 can be also calculated using Pauling’s formula: D (n) = D (1)−0.6logn34. Here, D (1) = 1.73 Å for the P-O bond, and D (n) is defined as the average of the two P–O distance (2.56 Å) at the translation state.…”