Yolk Inhibition of Lysozyme Activity in Egg White , ,

Abstract Yolk inhibits the lytic activity of lysozyme in egg white. Activity was determined by observing the rate of clearing of a cell suspension of M. lysodeikticus. Various levels of yolk were investigated. Observations included pH, salt, urea, temperature, and contrifugation effects on the inhibition of activity. Also, the relative inhibitory effects of two yolk fractions were considered. Degree of inhibition in the first minute of reaction was dependent upon yolk concentration and the ionic condition of the solution. Ten percent yolk produced total inhibition during the first minute of reaction, but lysis occurred after longer reaction times. Activity at various pH levels between 5.0 and 9.0 in egg white containing 5% yolk paralleled that of yolk-free egg white. Maximum activity was observed above pH 8.0. Centrifuging increased the activity of samples containing yolk at low pH values. Both salt and urea partially reactivated yolk-inhibited lysozyme. At pH 8.5, heating yolk-contaminated egg white below 56°C. had no effect on lysozyme activity. Lipovitellin or other constituents of the yolk granules inhibited lysozyme activity. The data suggest that the mechanism of inhibition involves electrostatic interaction between lysozyme and yolk components.