Further Characterization of PL-1 Phage-associated N-Acetylmuramidase of Lactobacillus Casei

1 Faculty of Pharmaceutical Sciences, Fukuoka University, Nanakuma, Jonan-ku, Fukuoka 814-01, Japan 2 Division of Biochemistry, Faculty of Fisheries, Nagasaki University, Nagasaki 852, Japan 3 Research Institute of Life Science, Yukijirushi Co. Ltd, Tochigiken 329-05, Japan ABSTRACT SUMMARY: The properties of an N -acetylmuramidase previously isolated from PL-1 phage lysates of Lactobacillus casei were studied in more detail. The enzyme differed from hen egg white lysozyme in its substrate specificity spectrum, in its physical and chemical nature and in other properties. The cell wall lytic action showed narrow specificity. The enzyme was most active against the phage's host. It was composed of a single polypeptide chain of M r about 37000 as estimated by gel filtration, SDS-PAGE and amino acid analysis. The circular dichroic spectrum showed that the peptide backbone of the enzyme molecule most probably had a mainly random structure. The protein was rich in neutral amino acids, and the enzyme had an isoelectric point of pH 5·0. The N-terminal sequence was determined up to 27 amino acid residues, showing alanine as the N-terminus; the C-terminus was a tyrosine residue.