ENZYME-SUBSTRATE COMPLEX OF LYSOZYME WITH CHITIN DERIVATIVES

The change in the ability of substrates to form a complex with lysozyme [EG 3.2.1.17] and the rate of hydrolysis were followed by substitution and deacetylation of chitin and glycol chitin. The substitution up to 70% at the 6-O-position of the N-acetylglucosamine residues of chitin did not affect the ability of the substrate to form the enzyme-substrate complex with lysozyme. Deacetylation of the 2-acetamide group of chitin or glycol chitin resulted in a great diminution in the rate of hydrolysis by lysozyme. The rate of hydrolysis of 50% deacetylated preparation was found to be about 20% of untreated glycol chitin by viscometry. In contrast, the ability to form the enzyme-substrate complex remained unchanged upon deacetylation up to 50%. Although further deacetylation resulted in the decrease in the amount of the enzyme-substrate complex, the ability of 90% deacetylated glycol chitin to form the complex was found to be 40%. It was concluded that the acctamidc group at binding site G is essential for binding of substrate, and the acetyl group at sites A and E may assist the enzyme-substrate complex formation. This is completely consistent with the result by X-ray diffraction studies by Phillips et al. © 1969 BY THE JOURNAL OF BIOCHEMISTRY.