Studies on Adenosine Triphosphate: Arginine Phosphotransferase

PURIFICATION AND REACTION MECHANISM

From the ¹ From the Department of Biochemistry, Australian National University, The John Curtin School of Medical Research, Canberra, Australia

A method is described for the preparation of highly purified arginine kinase from the tail muscle of the sea crayfish, Jasus verreauxi.

Initial velocity studies have been made of the arginine kinase reaction in both the forward and reverse directions. When the experimental data are plotted in double reciprocal form, families of parallel straight lines are obtained. Thus it has been concluded that the reaction mechanism is of the ping-pong type so that the product of the first reactant dissociates from the enzyme before the second substrate adds to the enzyme.

The conclusions with regard to the mechanism have been confirmed by the demonstration that an adenosine diphosphate-adenosine triphosphate exchange reaction occurs in the absence of the guanidino substrates and that an arginine-phosphoarginine exchange takes place in the absence of nucleotides. Whereas a divalent metal ion is required for the adenosine diphosphate-adenosine triphosphate exchange, it appears that it is not essential for the arginine-phosphoarginine exchange.

Higher concentrations of phosphoarginine have been shown to give rise to the inhibition of the reverse reaction.

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