title: 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.
abstract: 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.
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285-0438, USA. Zhao_Genshi@Lilly.com
authors.forename: G
authors.initials: G
authors.lastname: Zhao
authors.forename: W K
authors.initials: WK
authors.lastname: Yeh
authors.forename: R H
authors.initials: RH
authors.lastname: Carnahan
authors.forename: J
authors.initials: J
authors.lastname: Flokowitsch
authors.forename: T I
authors.initials: TI
authors.lastname: Meier
authors.forename: W E
authors.initials: WE
authors.lastname: Alborn
authors.forename: G W
authors.initials: GW
authors.lastname: Becker
authors.forename: S R
authors.initials: SR
authors.lastname: Jaskunas
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006868:Hydrolysis; D008969:Molecular Sequence Data; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000494:pharmacology*; D010458:Peptidyl Transferases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D013296:Streptococcus pneumoniae / Q000201:enzymology*; D018440:beta-Lactam Resistance; D047090:beta-Lactams
chemical_list: D000900:Anti-Bacterial Agents; D002352:Carrier Proteins; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D047090:beta-Lactams; C072223:PBP 2x protein, Streptococcus; D010458:Peptidyl Transferases