The αβ‐Methylene Analogues of ADP and ATP Act as Substrates for Creatine Kinase

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Abstract
The .alpha..beta.-methylene analogs of ATP and ADP, [.alpha..beta.CH2]ATP and [.alpha..beta.CH2]ADP, are substrates for [rabbit muscle] creatine kinase. However, the rate of the phosphoryl transfer reaction catalyzed is about 10-5 times lower than that with normal ATP. The affinities of the analogs (especially [.alpha..beta.CH2]ADP) for the enzyme are lower than those of the normal substrates. The equilibrium constant at 25.degree. C, measured using 31P NMR, for the reaction Mg[.alpha..beta.CH2]ATP + creatine .dblarw. Mg[.alpha..beta.Ch2]ADP + phosphocreatine + H+ is 2.2 .times. 10-12 M compared with a value of 2.5 .times. 10-10 M for the same reaction with the normal substrates, corresponding to a difference in .DELTA.G0 values of 11.7 kJ .cntdot. mol-1. It follows that .DELTA.G0 for the hydrolysis of the terminal phosphate group of Mg[.alpha..beta.CH2]ATP is less favorable by 11.7 kJ .cntdot. mol-1 than that for MgATP.