Turkey Egg White Lysozyme

Crystalline turkey egg white lysozyme has been prepared by a simple procedure consisting of adsorption on carboxymethylcellulose followed by elution with (NH4)2CO3 solution and crystallization from 5% NaCl solution. The twice crystallized enzyme gave a single peak when eluted from carboxymethylcellulose, and it migrated as a single band during disc electrophoresis. Separation of the tryptic peptides from reduced and S-carboxymethylated turkey egg white lysozyme has yielded peptides analogous to those of reduced and S-carboxymethylated chicken egg white lysozyme. It is found that the turkey enzyme amino acid sequence differs from that of the chicken lysozyme at a minimum of seven positions which are distributed over six of these tryptic peptides. The replacements detected from examination of these peptides are: Tyr for Phe3, Leu for His15, His for Gln41, Lys for Arg73, Ala for Val99, Gly for Asp101, and His for Gln121 of the chicken egg white lysozyme. The apparent occurrence of glycine as Residue 101 of turkey egg white lysozyme is especially interesting inasmuch as the x-ray crystallographic investigation of chicken egg white lysozyme and its complexes with certain inhibitors has led to the view that the carboxyl group of Asp101 is involved in binding substrates.