Appearance of a γ- d -Glutamyl-( l ) Meso -Diaminopimelate Peptidoglycan Hydrolase During Sporulation in Bacillus sphaericus

Abstract

Particulate preparations from sporulating cells of Bacillus sphaericus 9602 contained an endopeptidase activity that hydrolyzed the γ- d -glutamyl-( l ) meso -diaminopimelic acid linkages found in the spore cortical peptidoglycan of this organism. Diaminopimelic acid did not occur in the vegetative cell wall peptidoglycan, and the γ- d -glutamyl- l -lysine linkages found in this polymer were not hydrolyzed by the endopeptidase. The endopeptidase hydrolyzed (X)- l -alanyl-γ- d -glutamyl-( l ) meso -diaminopimelyl( l )- d -alanyl- d -alanine only after removal of the terminal d -alanine residue. The preparations contained an acyl- d -alanyl- d -alanine carboxypeptidase I activity which converted such pentapeptides into substrates for the endopeptidase and which was inhibited 50% by 4 × 10 ⁻⁷ M benzylpenicillin. This activity also hydrolyzed the analogous pentapeptide substrates containing l -lysine. The preparations also contained an acyl- l -lysyl- d -alanine carboxypeptidase II activity that was not active on the meso -diaminopimelic acid-containing analogue. Neither this activity nor the endopeptidase was inhibited by 10 ⁻³ M benzylpenicillin. The specificities of the carboxypeptidases were consistent with the exclusive presence of l -lysine C-termini in the vegetative peptidoglycan and of meso -diaminopimelyl- d -alanine C-termini in the spore cortical peptidoglycan of B. sphaericus 9602.