ABSTRACT
Enzymatic catalysis is distinguished by the involvement of non-covalent binding interactions between complexed substrate molecules and the enzyme active site. These binding interactions have the potential to act concertedly with each other during the act of complexation and with covalent bonding changes. The snug fit theory requires that all the reactive centres of the substrate be held against the reacting groups on the enzyme at the same time or during the period between exit or entry of the substrate from and to the active site. Pepsin was one of the first proteases to be studied as a pure protein but its assay technique for substrate hydrolysis has proved to be a large barrier to progress. Carbon carbon bond formation and fission reactions most often occur via attack of a nucleophilic carbon at an electrophilic carbon centre via aldol-type condensation reactions. These reactions are central to both primary and secondary metabolic processes.
