Molecular cloning of recombinant DNA : proceedings of the Miami winter symposia, January 1977 / edited by W.A. Scott, R. Werner ; sponsored by the Department of Biochemistry, University of Miami, School of Medicine, Miami, Florida.

Date:
1977
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Molecular cloning of recombinant DNA : proceedings of the Miami winter symposia, January 1977 / edited by W.A. Scott, R. Werner ; sponsored by the Department of Biochemistry, University of Miami, School of Medicine, Miami, Florida. Source: Wellcome Collection.

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    BIOCHEMICAL PASTIMES . . . AND FUTURE TIMES 7 Jones, Lipmann, Hilz, and Lynen Model Enzyme + ATP < ► Enzyme - AMP + PP. Enzyme - AMP + CoSH < ► Enzyme - SCoA ♦ AMP Enzyme - SCoA + acetate ► Enzyme + acetyl - SCoA г* Mg ATP + CoASH + acetate ► PPj + AMP t acetyl - SCoA Berg Model Mg Enzyme + ATP + acetate < ► Enzyme - (acetyl-AMP) + PPj Enzyme - (acetyl- AMP) + CoASH ■<—► acetyl-SCoA + AMP+ Enzyme ATP + CoASH + acetate •» ► acetyl-SCoA + AMP+PPj Figure 2 To shorten the tale, a few fractionation steps enriched the aceto-CoA kinase activity nearly a hundred-fold and vir¬ tually eliminated the АТР-РР^ exchange. Romberg's early skepticism had, in the end, been warranted, but was his expla¬ nation for the origin of the ATP-PPi exchange correct? I knew, as the overall reaction equation predicted, that there was an exchange of PPi and ATP when both of the other sub¬ strates, acetate and CoA were present. To determine if both acetate and CoA were essential for the ATP-PPi exchange each one was omitted from the reaction. I was flabbergasted to find that omission of CoA increased the rate of exchange and that leaving out acetate alone eliminated the ATP-PPi exchange completely. This observation suggested immediately that the aceto-CoA kinase catalyzed a reversible reaction between ATP and acetate resulting in the release of PP^; the most reason¬ able intermediate seemed to be a hitherto unknown mixed an¬ hydride, acetyl adenylate, strongly bound to the enzyme (11) (Fig. 2). Synthetic acetyl adenylate proved to be consider-