Partial purification and some properties of phi C2(W) lysin, a lytic enzyme produced by phage-infected cells of Streptococcus lactis C2.

The lytic enzyme present in phi C2(W) lysates was isolated by means of ion-exchange chromatography and further purified by gel filtration and ultrafiltration. The phage enzyme had an apparent pH optimum of 6.5-6.9 and was rapidly inactivated at temperatures greater than 47 degrees C. The apparent temperature optimum was 37 degrees C and Q10 and Ea values over the range 22-32 degrees C were 2.5 and 69.2 kJ/mol respectively. Monovalent and divalent cations activated the enzyme. Reduced -SH groups on the enzyme were required for lytic activity. Gel filtration revealed a mol. wt of approximately 46000. Strain-dependent differences in sensitivity of group N lactic streptococci to lysin were found. Group D streptococci were also lysed. Strains of three species of Leuconostoc, two species of Lactobacillus, one strain of Escherichia coli and of Micrococcus lysodeikticus were apparently resistant. Analysis of cell wall degradation products gave results which were consistent with the lysin having the specificity of an N-acetylmuramidase.