Peptidoglycan synthetic enzyme activities of highly purified penicillin-binding protein 3 in Escherichia coli: A septum-forming reaction sequence

Highly purified penicillin-binding protein 3 of Escherichia coli was shown to synthesize crosslinked peptidoglycan from the lipid-linked precursor, N-acetylglucosaminyl-N-acetylmuramyl(-pentapeptide)-diphosphoryl undecaprenol through two successive enzymatic reactions, glycan chain extension by peptidoglycan transglycosylase and crossbridge formation by β-lactam sensitive peptidoglycan transpeptidase. These two enzyme activities seemed to be properties of protein 3. The transpeptidase reaction was specifically sensitive to the β-lactam antibiotics that inhibited the formation of the septum in vivo. These results indicate that the peptidoglycan-synthetic enzyme activities of penicillin-binding protein 3 may be involved in the process of cell division.