Comparative studies of the active site region of lysozymes from eleven different sources

Abstract Lysozymes from 11 different sources were examined for their ability to react with the affinity label 2′,3′‐epoxypropyl β‐glycoside of di‐(N‐acetyl‐D‐glucosamine) and in some cases with the corresponding derivative of tri‐(N‐acetyl‐D‐glucosamine). Their fluorescence spectra, in the presence or absence of tri‐(N‐acetyl‐D‐glucosamine), and their transglycosylase activity were also examined. The results obtained suggest that these lysozymes can be classified into two groups: Group I includes the lysozymes derived from the egg‐whites of bobwhite quail, chachalaca, duck, hen, Japanese quail, ring‐necked pheasant and turkey, and from human leukemic urine; Group II includes the lysozymes from bacteriophage T4, goose egg‐white and papaya latex. The lysozymes of group I are irreversibly inactivated by the epoxypropyl β‐glycosides and exhibit similar fluorescence spectra which shift to the blue upon the addition of tri‐(N‐acetyl‐D‐glucosamine). Moreover, they catalyse the transfer of disaccharide residues from the bacterial cell wall tetra saccharide to N‐acetyl‐D‐glucosamine, D‐glucose, D‐mannose and L‐fucose, at rates which are similar for the different enzymes. It is concluded that the active sites of the enzymes of Group I are all similar, and that they differ from those of the other three lysozymes.