Engineering of the active site of human lysozyme: conversion of aspartic acid 53 to glutamic acid and tyrosine 63 to tryptophan or phenylalanine.

Three human lysozymes containing a mutation either at Asp-53 to Glu or at Tyr-63 to Trp or Phe were synthesized and examined for their immunological and enzymatical activities in comparison with the native one. All mutants were immunologically indistinguishable from native human lysozyme. The [Trp63] and [Phe63] mutants catalysed the hydrolysis of Micrococcus lysodeikticus cell wall and glycol chitin effectively, while the [Glu53] mutant displayed very low activity toward M. lysodeikticus cells and no detectable activity toward glycol chitin.