Present evidence is highly suggestive of a stepwise mechanism with a common initial step of HCO3 activation, for all enzymes that use HCO3 rather than CO2 as the substrate. This activated form of HCO3 appears to be the carbonic-phosphoric anhydride, although this has only been proved rigorously with carbamoyl phosphate synthetase. Further studies using isotope scrambling and other techniques will be necessary to establish conclusively that this is the case with the other enzymes.

This content is only available as a PDF.
You do not currently have access to this content.