A particular conformational change of Bacillus cereus penicillinase under the action of a new penicillin analogue pyrazocillin
| Autor: | Éva Badár, Istvan Koczka, István T. Horváth, I. Mile, Vilmos Csányi |
|---|---|
| Rok vydání: | 1970 |
| Předmět: |
Conformational change
Time Factors Chemical Phenomena Stereochemistry Bacillus cereus Penicillins Hydrolysis Non-competitive inhibition medicine Binding site chemistry.chemical_classification Binding Sites biology Temperature Substrate (chemistry) General Medicine Hydrogen-Ion Concentration biology.organism_classification Penicillin Chemistry Kinetics Enzyme Biochemistry chemistry Pyrazoles beta-Lactamase Inhibitors medicine.drug |
| Zdroj: | Biochimica et biophysica acta. 220(2) |
| ISSN: | 0006-3002 |
| Popis: | The effect of a new penicillin analogue, 1-(2,6-dichlorophenyl)-4-methyl-5-pyrazolyl penicillin, designated pyrazocillin, on penicillinase (penicillin amido-β-lactamhydrolase, EC 3.5.2.6) from Bacillus cereus 569/H has been studied. Pyrazocillin inhibits the enzyme according to a “mixed” type inhibition. the K i value was 1.1 · 10 −2 M . The K m value as calculated from the hydrolysis velocity of pyrazocillin was higher than 1 · 10 −2 M . In addition to the competitive inhibition the effect of the time-dependent inhibition of pyrazocillin has also been examined in detail. It has been established that penicillinase incubated with pyrazocillin but in the absence of substrate was partially inactivated. This inactivation can be reversed by dilution, but in contrast to the effect of penicillin analogues already known, the inactivating effect is not reversed by the substrate. Moreover, the conformation of the enzyme, which has low catalytic activity when partially inactivated by preincubation with pyrazocillin, is stabilized by the substrate, while with higher substrate concentrations the catalytic activity is further decreased. Based on this experimental evidence, the hypothesis of two substrate binding sites of the enzyme has been suggested. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|