FIGURE 6.

Proposed catalytic mechanisms of C₅-epi and heparin lyase II (34). Both C₅-epi-catalyzed (left) and heparin lyase II-catalyzed (right) reactions go through the same carbanion intermediate by abstracting the C₅ proton. This carbanion intermediate can be reprotonated (left) to produce epimerized product or proceed to an elimination reaction by breaking up the glycosidic bond (right). Left, the C₅ proton is shown in a circle, which can be ³H-labeled.