1.Evaluation of penicillin expandase mutants and complex substrate inhibition characteristics at high concentrations of penicillin G.
Linjun WU ; Keqiang FAN ; Junjie JI ; Keqian YANG
Chinese Journal of Biotechnology 2015;31(12):1690-1699
Penicillin expandase, also known as deacetoxycephalosporin C synthase (DAOCS), is an essential enzyme involved in cephalosporin C biosynthesis. To evaluate the catalytic behaviors of penicillin expandase under high penicillin G concentration and to identify mutants suitable for industrial applications, the specific activities of wild-type DAOCS and several mutants with increased activities toward penicillin G were determined by HPLC under high penicillin G concentrations. Their specific activity profiles were compared with theoretical predictions by different catalytic dynamics models. We evaluated the specific activities of wild-type DAOCS and previous reported high-activity mutants H4, H5, H6 and H7 at concentrations ranging from 5.6 to 500 mmol/L penicillin G. The specific activities of wild-type DAOCS and mutant H4 increased as penicillin G concentration increased, but decreased when concentrations of substrate go above 200 mmol/L. Other mutants H5, H6 and H7 showed more complex behaviors under high concentration of penicillin G. Among all tested enzymes, mutant H6 showed the highest activity when concentration of penicillin G is above 100 mmol/L. Our results revealed that the substrate inhibition to wild-type DAOCS' by penicillin G is noncompetitive. Other DAOCS mutants showed more complex trends in their specific activities at high concentration of penicillin G (>100 mmol/L), indicating more complex substrate inhibition mechanism might exist. The substrate inhibition and activity of DAOCS mutants at high penicillin G concentration provide important insight to help select proper mutants for industrial application.
Catalysis
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Intramolecular Transferases
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genetics
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Mutation
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Penicillin G
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pharmacology
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Penicillin-Binding Proteins
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genetics
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Streptomyces
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enzymology
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genetics
2.Antimicrobial Susceptibility Patterns and Macrolide Resistance Genes of beta-Hemolytic Viridans Group Streptococci in a Tertiary Korean Hospital.
Young UH ; Gyu Yel HWANG ; In Ho JANG ; Ohgun KWON ; Hyo Youl KIM ; Kap Jun YOON
Journal of Korean Medical Science 2007;22(5):791-794
The aim of this study was to investigate antimicrobial susceptibilities and macrolide resistance mechanisms of beta-hemolytic viridans group streptococci (VGS) in a tertiary Korean hospital. Minimum inhibitory concentrations (MICs) of seven antimicrobials were determined for 103 beta-hemolytic VGS isolated from various specimens. The macrolide resistance mechanisms of erythromycin-resistant isolates were studied by the double disk test and polymerase chain reaction (PCR). The overall resistance rates of beta-hemolytic VGS were found to be 47.5% to tetracycline, 3.9% to chloramphenicol, 9.7% to erythromycin, and 6.8% to clindamycin, whereas all isolates were susceptible to penicillin G, ceftriaxone, and vancomycin. Among ten erythromycin-resistant isolates, six isolates expressed a constitutive MLSB (cMLSB) phenotype, and each of the two isolates expressed the M phenotype, and the inducible MLSB (iMLSB) phenotype. The resistance rates to erythromycin and clindamycin of beta-hemolytic VGS seemed to be lower than those of non-beta-hemolytic VGS in our hospital, although cMLSB phenotype carrying erm(B) was dominant in beta-hemolytic VGS.
Ceftriaxone/pharmacology
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Chloramphenicol/pharmacology
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Clindamycin/pharmacology
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Cross Infection/*genetics
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*Drug Resistance, Bacterial
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Erythromycin/pharmacology
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Humans
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Immunoenzyme Techniques
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Korea
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Macrolides/*pharmacology
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Penicillin G/pharmacology
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Phenotype
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Polymerase Chain Reaction
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Tetracycline/pharmacology
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Vancomycin/pharmacology
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Viridans Streptococci/*genetics/*metabolism
3.Resistant analysis and cultivation results of 3 160 blood specimen.
Jin-xing ZHANG ; Dan-qian LU ; Jian-wen YI
Journal of Central South University(Medical Sciences) 2005;30(1):121-122
Adolescent
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Adult
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Aged
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Aged, 80 and over
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Azithromycin
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pharmacology
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Bacteremia
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microbiology
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Child
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Child, Preschool
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Culture Media
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Drug Resistance, Bacterial
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Drug Resistance, Multiple, Bacterial
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Escherichia coli
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drug effects
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isolation & purification
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Female
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Humans
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Infant
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Infant, Newborn
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Male
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Methicillin Resistance
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Middle Aged
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Penicillin G
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pharmacology
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Salmonella paratyphi A
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drug effects
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isolation & purification
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Staphylococcus aureus
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drug effects
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isolation & purification
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Staphylococcus epidermidis
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drug effects
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isolation & purification