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Peptidoglycans synthesized by a membrane preparation of Micrococcus luteus

By incubation of cell-free particulate preparations from Micrococcus luteus with nucleotidic precursors uridine 5'-diphosphate-N-acetylglucosamine and uridine 5'-diphosphate-N-acetylmuramic acid-L-Ala-D-iso-Glu-L-Lys-D-Ala-D-Ala, several types of peptidoglycans were obtained: soluble peptidoglycan, insoluble peptidoglycan bound to the membrane and solubilized by trypsin, and peptidoglycan, which remained insoluble after the action of trypsin. The structure of each type of peptidoglycan was studied by action of lytic enzymes and separation of the fragments on Sephadex. Soluble peptidoglycans consist of a mixture of un-cross-linked polymers of various molecular weights. Trypsin-solubilized peptidoglycans are also a mixture of polymers of various sizes. They contain a preponderance of un-cross-linked material and some bridges with dimer peptides. Insoluble peptidoglycans, after the action of trypsin, contain about 50% of un-cross-linked peptide residues; in the other moiety, peptide units are cross-linked by D-Ala leads to L-Lys and D-Ala leads to L-Ala bonds which characterize the natural peptidoglycan. Therefore, the cell-free particulate preparation possesses the whole enzymatic system necessary for synthesis of cross-linked peptidoglycan.