Transient-Phase Studies on the Arginine Kinase Reaction

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Abstract
The initial formation of arginine phosphate by [Homarus vulgaris] arginine kinase was studied in the time range 2.8-50 ms by the quenched-flow method. A transient burst phase of production formation was obtained, the amplitude of which was temperature-dependent. At 35.degree. C it was 0.64 mol arginine phosphate/mol arginine kinase and at 12.degree. C, 0.25 mol/mol. These results show that for the reaction pathway of arginine kinase the rate-limiting step follows the formation of arginine phosphate on the enzyme. This is in contrast to the [vertebrate] creatine kinase reaction where no transient phase was observed. The rate-limiting step on the arginine kinase reaction pathway is only slightly affected by temperature: the change in kcat [catalytic constant] with temperature is due to a change of an equilibrium constant pertaining to at least 2 previous steps.