J Slezák

Bio: J Slezák is an academic researcher. The author has contributed to research in topics: Enzyme inducer & Phenylacetic acid. The author has an hindex of 1, co-authored 1 publications receiving 28 citations.

Penicillinamidohydrolase in Escherichia coli. III. Catabolite repression, diauxie, effect of cAMP and nature of the enzyme induction.

Abstract: Synthesis of penicillinamidohydrolase (penicillin acylase, EC 3.5.1.11) inEscherichia coli is subjected to the absolute catabolite repression by glucose and partial repression by acetate. Both types of catabolite repression of synthesis of the enzyme inEscherichia coli are substantially influenced by cyclic 3,′5′-adenosinemonophosphate (cAMP). Growth diauxie in a mixed medium containing glucose and phenylaoetic acid serving as carbon and energy sources is overcome by cAMP. cAMP does not influence the basal rate of the enzyme synthesis (without the inducer). Derepression of synthesis of penicillinamidohydrolasa by cAMP in a medium with glucose and inducer (phenylacetic acid) is associated with utilization of the inducer, due probably to derepression of other enzymes responsible for degradation of phenylacetic acid. Lactate can serve as a “catabolically neutral” source of carbon suitable for the maximum production of penicillinamidohydrolase. The gratuitous induction of the enzyme synthesis in a medium with lactate as the carbon and energy source and with phenylacetic acid is not influenced by cAMP; however, cAMP overcomes completely the absolute catabolite repression of the enzyme synthesis by glucose.

Characterization and use of a penicillin acylase biocatalyst.

Abstract: A complete characterization of a penicillin acylase biocatalyst is presented, including the determination of physicochemical and kinetic parameters. Stability studies are detailed in terms of both storage temperature and pH as well as operational stability after 150 batch reactions of two hours duration each. An Arrhenius-type model was used to simulate the effect of pH on biocatalyst stability. A kinetic model is proposed to describe batch and continuous stirred tank reactors and to predict the long-term behavior of the process.

Carbon regulation and the role in nature of the Escherichia coli penicillin acylase (pac) gene

Abstract: Summary Quantitative analysis of specific pac mRNA and a lacZ fusion to the 5’-terminal region of the pac gene demonstrated that both phenylacetic acid induction and catabolite repression by glucose are involved, at the transcriptional level, in the regulation of the pac gene. The studies presented here suggest that this regulation is also present in Escherichia coli transformed strains in which the pac gene was not originally present. Analysis of the nucleotide sequence of the 5′-terminal region of this gene, with a statistical algorithm, confirms that the putative promoter previously proposed by our group is the most feasible within this region. We demonstrate that penicillin acylase activity can confer on E. coli the ability to use penicillin G as a metabolic substrate, by detaching the phenylacetic group which can be used as a carbon source. Based on these data, the regulation properties of the pac gene studied in this work, and the specificity profile of the penicillin acylase enzyme we suggest a role for it in E. coli as a scavenger enzyme for phenylacetylated compounds.

Improved penicillin amidase production using a genetically engineered mutant of escherichia coli ATCC 11105

Abstract: Penicillin G amidase (PGA) is a key enzyme for the industrial production of penicillin G derivatives used in therapeutics. Escherichia coli ATCC 11105 is the more commonly used strain for PGA production. To improve enzyme yield, the authors constructed various recombinant E. coli HB 101 and ATCC 11105 strains. For each strain, PGA production was determined for various concentrations of glucose and phenylacetic acid (PAA) in the medium. The E. coli strain, G271, was identified as the best performer (800 U NIPAB/L). This strain was obtained as follows: an E. coli ATCC 11105 mutant (E. coli G133) was first selected based on a low negative effect of glucose on PGA production. This mutant was then transformed with a pBR322 derivative containing the PGA gene. Various experiments were made to try to understand the reason for the high productivity of E. coli G271. The host strain, E. coli G133, was found to be mutated in one (or more) gene(s) whose product(s) act(s) in trans on the PGA gene expression. Its growth is not inhibited by high glucose concentration in the medium. Interestingly, whereas glucose still exerts some negative effect on the PGA production by E. coli G133, PGA production by itsmore » transformant (E. coli G271) is stimulated by glucose. The reason for this stimulation is discussed. Transformation of E. coli G133 with a pBR322 derivative containing the HindIII fragment of the PGA gene, showed that the performance of E. coli G271 depends both upon the host strain properties and the plasmid structure. Study of the production by the less efficient E. coli HB101 derivatives brought some light on the mechanism of regulation of the PGA gene.« less

Penicillin acylases. An update

Abstract: Etude portant sur la purification, les methodes de dosage, les proprietes physicochimiques et cinetiques de l'enzyme. On decrit aussi brievement sa biosynthese