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J. Bacteriol., May 1997, 3181-3187, Vol 179, No. 10
Y Chen, S Miyata, S Makino and R Moriyama
The exudate of fully germinated spores of Clostridium perfringens S40 in
0.15 M KCI-50 mM potassium phosphate (pH 7.0) was found to contain another
spore-lytic enzyme in addition to the germination-specific amidase
previously characterized (S. Miyata, R. Moriyama, N. Miyahara, and S.
Makino, Microbiology 141:2643-2650, 1995). The lytic enzyme was purified to
homogeneity by anion-exchange chromatography and shown to be a muramidase
which requires divalent cations (Ca2+, Mg2+, or Mn2+) for its activity. The
enzyme was inactivated by sulfhydryl reagents, and sodium thioglycolate
reversed the inactivation by Hg2+. The muramidase hydrolyzed isolated spore
cortical fragments from a variety of wild-type organisms but had minimal
activity on decoated spores and isolated cell walls. However, the enzyme
was not capable of digesting isolated cortical fragments from spores of
Bacillus subtilis ADD1, which lacks muramic acid delta-lactam in its
cortical peptidoglycan. This indicates that the enzyme recognizes the
delta-lactam residue peculiar to spore peptidoglycan, suggesting an
involvement of the enzyme in spore germination. Immunochemical studies
indicated that the muramidase in its mature form is localized on the
exterior of the cortex layer in the dormant spore. A gene encoding the
muramidase, sleM, was cloned into Escherichia coli, and the nucleotide
sequence was determined. The gene encoded a protein of 321 amino acids with
a deduced molecular weight of 36,358. The deduced amino acid sequence of
the sleM gene indicated that the enzyme is produced in a mature form. It
was suggested that the muramidase belongs to a separate group within the
lysozyme family typified by the fungus Chalaropsis lysozyme. A possible
mechanism for cortex degradation in C. perfringens S40 spores is discussed.
Copyright © 1997, American Society for Microbiology
Molecular characterization of a germination-specific muramidase from Clostridium perfringens S40 spores and nucleotide sequence of the corresponding gene
Department of Applied Biological Sciences, School of Agricultural Sciences, Nagoya University, Aichi, Japan.
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