Biochemical characterization of penicillin-resistant and -sensitive penicillin-binding protein 2x transpeptidase activities of Streptococcus pneumoniae and mechanistic implications in bacterial resistance to beta-lactam antibiotics.

Zhao G, Yeh WK, Carnahan RH, Flokowitsch J, Meier TI, Alborn WE, Becker GW, Jaskunas SR
J Bacteriol. 1997 179 (15): 4901-8

PMID: 9244281 · PMCID: PMC179340 · DOI:10.1128/jb.179.15.4901-4908.1997

To understand the biochemical basis of resistance of bacteria to beta-lactam antibiotics, we purified a penicillin-resistant penicillin-binding protein 2x (R-PBP2x) and a penicillin-sensitive PBP2x (S-PBP2x) enzyme of Streptococcus pneumoniae and characterized their transpeptidase activities, using a thioester analog of stem peptides as a substrate. A comparison of the k(cat)/Km values for the two purified enzymes (3,400 M(-1) s(-1) for S-PBP2x and 11.2 M(-1) s(-1) for R-PBP2x) suggests that they are significantly different kinetically. Implications of this finding are discussed. We also found that the two purified enzymes did not possess a detectable level of beta-lactam hydrolytic activity. Finally, we show that the expression levels of both PBP2x enzymes were similar during different growth phases.

MeSH Terms (10)

Anti-Bacterial Agents beta-Lactam Resistance beta-Lactams Carrier Proteins Hydrolysis Molecular Sequence Data Penicillin-Binding Proteins Penicillins Peptidyl Transferases Streptococcus pneumoniae

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