There Is No Experimental Evidence for Endocyclic Cleavage in the Action of e → e (Retaining β) Glycopyranosidases, and Much Against It

A recent review by Franck (1) in this journal reappraised some of the evidence for exocyclic cleavage during catalysis by β-glycopyranosidases in favor of an endocyclic cleavage mechanism. The purpose of this letter is to indicate briefly how this reappraisal appears to be based upon misconceptions in logic, chemistry, and biology.