Showing papers on "Penicillin amidase published in 1992"

Effects of site-directed mutations on processing and activities of penicillin G acylase from Escherichia coli ATCC 11105.

Abstract: Penicillin G acylase from Escherichia coli ATCC 11105 is synthesized from its precursor polypeptide into a catalytically active heterodimer via a complex posttranslational processing pathway. Substitutions in the pair of aminoacyl residues at the cleavage site for processing the small and large subunits were made. Their processing phenotypes and penicillin G acylase activities were analyzed. By the introduction of a prolyl residue at either position, the processing of the small subunit was blocked without a change in enzymatic activity. Four other substitutions had no effect. At the site for processing the large subunit, four substitutions out of the seven examined blocked processing. In general, penicillin G acylase activity seemed to be proportional to the efficiency of the large-subunit-processing step. Ser-290 is an amino acid critical for processing and also for the enzymatic activity of penicillin G acylase. In the mutant pAATC, in which Ser-290 is mutated to Cys, the precursor is processed, but there is no detectable enzymatic activity. This suggests that there is a difference in the structural requirements for the processing pathway and for enzymatic activity. Recombination analysis of several mutants demonstrated that the small subunit can be processed only when the large subunit is processed first. Some site-directed mutants from which signal peptides were removed showed partial processing phenotypes and reduced enzymatic activities. Their expression showed that the prerequisite for penicillin G acylase activity is the efficient processing of the large subunit and that the maturation of the small subunit does not affect the enzymatic activity.

N-(4′-Hydroxyphenylacetyl)palytoxin: A Palytoxin Prodrug That Can Be Activated by a Monoclonal Antibody-Penicillin G Amidase Conjugate

Abstract: Palytoxin (PTX), one of the most toxic nonprotein molecules known, is cytotoxic at picomolar concentrations against a wide variety of cell types. In contrast to most cytotoxins, PTX exerts its activity extracellularly. A method for targeting PTX to tumor cells is described in which a monoclonal antibody-enzyme conjugate activates a PTX prodrug at surfaces of tumor cells. The prodrug, N-(4'-hydroxyphenylacetyl)palytoxin (NHPAP), was prepared by reacting PTX with an active ester of 4-hydroxyphenylacetic acid. NHPAP was 1000 times less toxic than PTX to a panel of carcinoma and lymphoma cell lines. The cytotoxic activity of the combination of penicillin G amidase from Escherichia coli with NHPAP was equal to PTX. Two cell lines that were multidrug resistant showed no enhanced resistance to NHPAP +/- penicillin G amidase. Immunologically specific activation of NHPAP took place when H2981 cells (L6 antigen positive) were treated with the monoclonal antibody conjugate L6-penicillin G amidase followed by NHPAP. This system is distinguished from other prodrug activation schemes, since the released drug exerts its activity extracellularly, has high potency, and may be able to overcome the multidrug resistant phenotype.

Studies on the isolation of penicillin acylase from Escherichia coli by aqueous two‐phase partitioning

Abstract: A method of enzyme release and aqueous two-phase extraction is described for the separation of penicillin acylase from Escherichia coli cells. Butyl acetate, 12% (v/v), treatment combined with freeze–thawing gives up to 70% enzyme release. For polyethylene glycol (PEG) + phosphate two-phase extraction systems the enzyme purity and yield were rather low. Modified PEG, including PEG–ampicillin, PEG–aniline, PEG–phosphate, and PEG–trimethylamine, were synthesized and used in aqueous two-phase systems; PEG–trimethylamine is the most satisfactory. A system containing 12% (w/w) PEG4000, 8% (w/w) of which is PEG–trimethylamine, with 0.7M potasium phosphate at pH 7.2, resulted in the enzyme selective partition being greatly enhanced by charge directed effects. Possible mechanisms for the separation process are discussed. © 1992 John Wiley & Sons, Inc.

Penicillin G acylase fromKluyvera citrophila new choice as industrial enzyme

Abstract: We propose a new and integrated method for the evaluation of industrial enzymes. The application of this method to the enzyme penicillin G acylase fromKlyvera citrophila shows very interesting industrial propects. This acylase presents a much better stability agains heat, pH or organic cosovents as compared with the more popular enzyme fromEscherichia coli. In addition, this enzyme is very easy to immobilize through its amine groups and to stabilize through multipoint covalent attachment on activated pre-existing supports.

Hydrolysis of penicillin G by combination of immobilized penicillin acylase and electrodialysis

Abstract: Phenylacetic acid, as inhibitory product, was formed from a hydrolysis of penicillin G by immobilized penicillin acylase. In this article, electrodialysis was applied to remove phenylacetic acid continuously from the reaction mixture and to enhance an efficiency of the reaction. When 268 and 537 mM of penicillin G solution were used as the substrate, the concentration of phenylacetic acid in the reaction mixture could be maintained at less than 81 and 126 mM, respectively, and eventually, 86% and 88% of phenylacetic acid produced were removed from the reaction mixture at the end of the hydrolysis, respectively. Times required to reach 96% and 94.8% conversion from 268 and 537 mM of initial penicillin G could be reduced to 65% and 64% respectively, by means of electrodialysis; while 3.0% and 4.3% of initial penicillin G of 268 and 537 mM were permeated out of the reaction chamber during the hydrolysis, respectively. However, a loss of penicillin G by permeation could be reduced from 4.3% to 3.4% by a repeated addition of penicillin G.

The primary structure of Providencia rettgeri penicillin G amidase gene and its relationship to other gram negative amidases.

Abstract: The nucleotide sequence of Penicillin G amidase (PA,E.C.3.5.1.11) of Providencia rettgeri was determined. We aligned our P. rettgeri PA with other known Gram negative periplasmically located beta-lactam amidases. The analysis revealed a high homology with other Enterobacteric amidases (60%-65%), while with similar Pseudomonas sp. amidases the homology exceeded 25%. These homologies indicate their common ancestry.

Reconstitution in vivo of penicillin G acylase activity from separately expressed subunits

Abstract: Penicillin G acylase from Escherichia coli ATCC11105 is synthesized as a precursor polypeptide with a signal sequence for secretion into the periplasm and an endopeptide separating two subunit domains. Proteolytic processing leads to mature, heterodimeric penicillin G acylase. We have shown that the α- and β-subunits of the enzyme, which have no detectable enzymatic activity on their own, can reconstitute enzyme activity when their genes are put into an E. coli host on separate plasmids. Activity is reconstituted in the cytoplasm whereas normally processing and formation of the active heterodimer occurs in the periplasm. Enzyme activity can reach levels close to wild type in the strain used. The activity recovered from a combination of α-subunit linked to a 54-amino-acid endopeptide and β-subunit was lower than with the subunits alone.

Changing glycine 21 for glutamic acid in the beta-subunit of penicillin G acylase from Kluyvera citrophila prevents protein maturation.

Abstract: Active penicillin acylase from Kluyvera citrophila strain ATCC 21 285 consists of two different α-and β-subunits derived from a single precursor by post-translational processing. Using the chemical mutagen hydroxylamine we have treated plasmid pYKD59 containing the active penicillin acylase gene (pga) from K. citrophila and have generated different point mutant penicillin acylase genes, one producing a muturation deficient precursor. This point mutation has changed the gylcine 310 residue of the precursor for a glutamic acid (residue number 21 of the mature β-subunit). The introduction of a charged residue in this position did not prevent translocation of the precursor to the periplasm but the resultant molecule was not able to undergo subsequent post-translational modification to yield the active protein.

Co‐existence of β‐lactamase and penicillin acylase in bacteria; detection and quantitative determination of enzyme activities

Abstract: Twenty-six bacteria were examined for the presence of penicillin acylase and beta-lactamase. A copper reducing assay, which was sensitive in the analytical range 2-20 micrograms/ml, was used for determination of penicilloates and a fluorescamine assay was used to determine 6-aminopenicillanic acid concentrations when both substances were produced by the action of the enzymes on a single substrate. Seventeen bacteria contained beta-lactamases, six contained penicillin acylases and four contained both enzymes. Two bacteria contained a Type 1 penicillin acylase and four bacteria contained a Type II enzyme. No ampicillin acylases were detected. All beta-lactamases were constitutive enzymes in those organisms where both enzymes co-existed. Bacillus subtilis and B. cereus produced inducible and extracellular beta-lactamases. Acinetobacter calcoaceticus ATCC 21288 produced a constitutive beta-lactamase which was detected extracellularly.

Method of purification of penicillin amidase using phenylbutylamine-eupergit

Abstract: An enzyme is purified by absorbing enzymes in an aqueous solution on a specific carrier material T-PbA to which is covalently bound phenyl butylamine ligand groups.

Effect of microenvironment of oxirane groups on the immobilization of penicillin G acylase

Abstract: Macroporous beaded terpolymers containing oxirane groups were synthesized for immobilization of penicillin G acylase. The effect of incorporation of various monomers such as hydroxyethyl methacrylate and methyl methacrylate, and the effect of crosslinking agents such as ethylene glycol dimethacrylate and divinyl benzene on binding and expression of penicillin G acylase were studied. It was found that hydrophilic and hydrophobic microenvironments decrease the binding efficiency as well as the expression of the bound enzyme. The binding efficiency decreases less dramatically with increasing hydrophobicity.

Purification of Penicillin Amidohydrolase, an Enzyme for Semisynthetic Procedures

Abstract: Penicillin amidohydrolase (EC 35111) is one of the few enzymes used successfully for deprotection of primary amino groups of semisynthetic peptides The available material is usually contamined by endo- and exopeptidases We managed to prepare the enzyme devoid of trypsin- and chymotrypsin-like activities using affinity chromatography with specific ligands: Gly-D-Phe-Phe-Tyr-Thr-Pro-Lys-Thr (the fF peptide) and Leu-Gly-Val-D-Arg-Arg-Gly-Phe (the rR peptide) For further purification of the enzyme affinity chromatography with N-phenylacetyl-D-tert-Leu as a ligand was used

Enzymic Synthesis Design and Enzymic Synthesis of Aspartame.

Abstract: An enzymic synthesis of aspartame (H-Asp-Phe-OMe) has been designed and realized based on the structure-activity study of thermolysin and penicillin amidase hydrolysis of its p-substituted phenylacetyl derivatives. These compounds meet the structural and energetic requirements of two enzymic binding sites The peptide sweetener has been prepared by thermolysin - catalyzed condensation of the p-substituted phenylacetyl-Asp-OH and H-Phe-OMe followed by penicillin amidase - catalyzed deprotection of the resulted aspartame precursors.