The autolytic ('suicidase') system of Enterococcus hirae: from lysine depletion autolysis to biochemical and molecular studies of the two muramidases of Enterococcus hirae ATCC 9790.

摘要: Autolysis of Enterococcus hirae ATCC 9790 is the result action endogenous enzymes that hydrolyze bonds in protective and shape-maintaining cell wall peptidoglycan. It thought these potentially suicidal play a positive role(s) growth division are expressed as autolysins when assembly and/or repair inhibited. E. possesses two autolytic enzymes, both which muramidases. Although they same bond hen egg-white lysozyme, high-molecular-mass, complex enzymes. Muramidase-1 synthesized zymogen, requiring protease activation. glucoenzyme also multiply nucleotidylated with an unusual nucleotide, 5-mercaptouridine monophosphate. Muramidase-2 almost certainly product separate gene. The deduced amino acid sequence cloned gene for extracellular muramidase-2 showed several features. appears to be two-, or perhaps three-domain protein putative glycosidase-active site near N-terminal end six 45-amino-acid-long repeats at C-terminal presumed involved high-affinity binding insoluble peptidoglycan substrate. binds penicillin low affinity. presence groupings characteristic serine-active β-lactam-interactive proteins consistent possible penicillin-binding, third domain. Indirect evidence has been obtained. However, proof such awaits modern genetic, molecular, biochemical analyses.