Chemical Evidence for the Phillips Model of the Action of Hen Egg White Lysozyme

Abstract

A THREE-dimensional model of the ES-complex formed between a chito-oligosaccharide and hen egg white lyso-zyme was presented by Blake et al. as a result of X-ray crystallographic investigations¹. We reported that partially O-carboxymethylated chitin, which had satisfactory solubility, was highly susceptible to the action of lysozyme² where the contents of the carboxymethyl groups were very roughly 0.3 mole/mole of N-acetoglucosamine residue. It is to be expected that the fairly bulky O-substituents will not permit such a free binding as that between unsubstituted chito-oligosaccharides and the enzyme, but will force the enzyme to select some suitable portions of the substrate molecules for making the ES-complex. Although it is impossible to know the exact location of the O-substituents on the high molecular substrate, the location of those on the enzymatic reaction products—which are low molecular compounds—can be determined. The orientation of the O-substituents in the product molecules must be reflexions of the conformation of the binding sub-sites in the ES-complex, because those suitable portions of the substrate molecule must have been fitted in the sub-sites before being released as low molecular saccharides.