Effect of Diinethylsulfoxide on ATP Synthesis by Mitochondrial Soluble F1-ATPase1

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Abstract
F 1 -ATPase isolated from bovine heart mitochondria catalyzes the synthesis of enzyme-bound ATP from externally added ADP and P 1 in the presence of dimethylsulfoxide (DMSO) (Sakamoto, J. & Tonomura, Y. (1983) J. Biochem.93 , 1601–1614). When the concentration of DMSO in the reaction medium was decreased from 40% to 10% (w/v), the maximal amount of ATP formed decreased from 0.50 to 0.14 mol/mol F 1 and the P 1 concentration required for the half-maximal amount of ATP formed increased from 0.7 to 11 m. On the other hand, the ADP concentration required for the half-maximal value and the rate of ATP formation were unaffected by the decrease in the DMSO concentration. These results suggest that DMSO increases the affinity of F 1 for P 1 and shifts the equilibrium from the enzyme-ADP-P 1 complex to the enzyme-ATP complex during the ATP synthesis.