Considering Alcaligenes faecalis pencillin G acylase(AfPGA), which possesses the attractive characteristics for beta-lactam antibiotics conversions, the gene of PGA was cloned into an expressing vector pKKFPGA. The recombinant plasmid contained multicopy replicon(COLE 1), trc promoter, AfPGA gene, rrnB transcript terminator and ampicillin marker transformed Escherichia coli DH5alpha. As both the recombinant plasmid and the host DH5alpha had no laclq gene, the trc promoter was always active and the AfPGA could be constitutively expressed without IPTG induction in the host DH5alpha. In the shaking flask, the recombinant cell was inoculated into the fermentation medium (tryptone 10g/L, yeast extract 5g/L, MgSO4 x 7 H2O 1g, KH2 PO4 2g/L, K2HPO4 x 3H2O 5g/L, Na2HPO4 x 12H2O 7g/L, (NH4)2SO4 1.2g/L, NH4Cl 0.2 g/L, NaCl 0.1g/L, dextrin 30g/L) and cultured at 28 degrees C for 20h. The production of AfPGA reached 2,590u/L(NIPAB method), with a cell-density-specific activity of more than 300(u/L)/A600, this yield increased 432 fold higher than the native expression of Alcaligenes faecalis . Without ammonium sulphate fractionation and dialysis, the supernatant of crude extract was directly loaded on DEAE-Sepharose CL 6B column equilibrated by phosphate buffer (50mmol/L, pH7.8), and the enzyme fraction was not absorbed on the column but impurities were absorbed. Subsequently the effluent was added ammonium sulphate to 1mol/L and loaded on Butyl-Sepharose CL 4B column equilibrated by 50mmol/L phosphate buffer pH7.8-1mol/L ammonium sulphate. The enzyme was eluted as concentration of ammonium sulphate in phosphate buffer decreased to 0, PGA was eluted. After these two column chromatography, the enzyme was enriched 20 times with a 91% activity recovery. The purified enzyme had a specific activity of 68.6u/mg protein. However, the overproduction of PGA was often limited by translocation and/or periplasmic processing steps, subsequently resulted in intracellular accumulation of various types of PGA precursors and then formed inclusion bodies in the cytoplasm and/or periplasm. In this study, 5% PGA precursors formed as inclusion bodies in the cytoplasm while no inclusion bodies formed in the periplasm. It suggested most PGA precursors were transported to the periplasm and matured to active PGA and also explained why PGA gene was highly expressed in the host DH5alpha. On the other hand, inclusion bodies in the cytoplasm indicated that the maturation of PGA in the host DHSalpha was limited by the translocation step.
Alcaligenes faecalis ; enzymology ; Blotting, Western ; Escherichia coli ; genetics ; Penicillin Amidase ; genetics ; isolation & purification ; Recombinant Proteins ; biosynthesis ; isolation & purification

BACKGROUND: Resistance to penicillin of Streptococcus pneumoniae in clinical isolates has occurred by the development of altered penicillin-binding proteins (PBPs) that have greatly decreased affinity for antibiotics and has been encountered with increasing frequency in Korea. In this study, the identification of altered PBPs of S. pneumoniae in clinical isolates by using polymerase chain reaction (PCR) and relationship of PCR with the conventional antibiotic susceptibility test of penicillin were evaluated. METHODS: Thirty isolates of S. pneumoniae from clinical specimens were used. Four sets of PCR primers of penicillin-sensitive and -resistant S. pneumoniae were designed to amplify (i) PBP 2BS: a 360 base pair fragment of the PBP 2B gene, (ii) PBP 2BCA: a 350 base pair fragment of the class A mutations present in PBP 2B gene, (iii) PBP 2BCB: a 295 base pair fragment of the class B mutations present in PBP 2B gene, and (iv) PBP 1AR: a 434 base pair fragment of the PBP 1A gene. In addition, a set of primers that amplify 273 base pair of the autolysin gene (ALY) was applied in combination with the above to identify S. pneumoniae. PCR results were compared with antibiotic susceptibility test (disk diffusion test and penicillin MIC). RESULT: Among 30 clinical isolates tested, 80% of isolates were penicillin resistant. The results of antibiotic susceptibility test were same as those of PCR methods. Among 24 penicillin resistant isolates detected by PCR methods, 5 isolates revealed PBP 2BCB gene, but 19 isolates revealed both of PBP 2BCB and 1AR genes. Five isolates with PBP 2BCB gene showed lower range of penicillin MIC (0.19 ~ 1.0 g/mL) than 19 isolates with PBP 2BCB and 1AR genes (0.75 ~ 4.0 g/mL). CONCLUSION: Detection of altered PBP genes of S. pneumoniae by PCR may be performed for the study of penicillin resistance. This study indicates that more altered PBPs in 1AR genes are related with higher MICs.
Anti-Bacterial Agents ; Base Pairing ; Diffusion ; Korea ; N-Acetylmuramoyl-L-alanine Amidase ; Penicillin Resistance ; Penicillin-Binding Proteins ; Penicillins ; Pneumonia ; Polymerase Chain Reaction* ; Streptococcus pneumoniae* ; Streptococcus*

Immobilized penicillin acylase was used for bioconversion of penicillin PG into 6-APA in aqueous two-phase systems consisting of a light-sensitive polymer PNBC and a pH-sensitive polymer PADB. Partition coefficients of 6-APA was found to be about 5.78 in the presence of 1% NaCl. Enzyme kinetics showed that the reaction reached equilibrium at roughly 7 h. The 6-APA mole yields were 85.3% (pH 7.8, 20 degrees C), with about 20% increment as compared with the reaction of single aqueous phase buffer. The partition coefficient of PG (Na) varied scarcely, while that of the product, 6-APA and phenylacetic acid (PA) significantly varied due to Donnan effect of the phase systems and hydrophobicity of the products. The variation of the partition coefficients of the products also affected the bioconversion yield of the products. In the aqueous two-phase systems, the substrate, PG, the products of 6-APA and PA were biased in the top phase, while immobilized penicillin acylase at completely partitioned at the bottom. The substrate and PG entered the bottom phase, where it was catalyzed into 6-APA and PA and entered the top phase. Inhibition of the substrate and products was removed to result in improvement of the product yield, and the immobilized enzyme showed higher efficiency than the immobilized cells and occupied smaller volume. Compared with the free enzyme, immobilized enzyme had greater stability, longer life-time, and was completely partitioned in the bottom phase and recycle. Bioconversion in two-phase systems using immobilized penicillin acylase showed outstanding advantage. The light-sensitive copolymer forming aqueous two-phase systems could be recovered by laser radiation at 488 nm or filtered 450 nm light, while pH-sensitive polymer PADB could be recovered at the isoelectric point (pH 4.1). The recovery of the two copolymers was between 95% and 99%.
Catalysis ; Enzymes, Immobilized ; metabolism ; Hydrogen-Ion Concentration ; Kinetics ; Penicillanic Acid ; analogs & derivatives ; chemistry ; metabolism ; Penicillin Amidase ; metabolism ; Penicillin G ; chemistry ; metabolism ; Phase Transition ; Polymers ; chemistry ; Substrate Specificity

The nucleotide sequence and N-, C-terminal amino acid sequences of alpha,beta-subunit of glutaryl 7-ACA acylase C130 from Pseudomonas sp. 130 were determined. The alignment of the acylase C130 with the other acylases shows that it has high homology with the acylases from Pseudomonas sp. GK16 and C427, but low homology with the others. There is large difference in the N-terminal of alpha-subunit, while the N-terminal of beta-subunit has significant conservation.
Amino Acid Sequence ; Base Sequence ; DNA, Bacterial ; analysis ; Genes, Bacterial ; Molecular Sequence Data ; Penicillin Amidase ; genetics ; Pseudomonas ; enzymology ; genetics ; Sequence Homology, Amino Acid ; Sequence Homology, Nucleic Acid

The effect of dual promoters on recombinant protein production from bacterial phage based Bacillus subtilis expression system was investigated. Alpha amylase (from Bacillus amyloliquefaciens) and penicillin acylase (from Bacillus megaterium) were selected as the indicating enzymes. Both the promoterless genes and the promoter-bearing genes were isolated through PCR amplification with properly designed primers, and were inserted into plasmid pSG703 that contains the lacZ-cat expression cartridge. The lysogenic B. subtilis (phi105 MU331) was transformed with the resultant recombinant plasmids, and the heterologous genes were thereby integrated into the chromosommal DNA of B. subtilis via homologous recombination. The transformants were designated as B. subtilis AMY1, B. subtilis AMY2, B. subtilis PA1, and B. subtilis PA2, respectively. In the recombinant B. subtilis strains, the inserted sequences were located down stream of a strong phage promoter that could be activated by thermal induction. In B. subtilis AMY1 and B. subtilis PA1, transcription of the heterologous genes was only initiated by the phage promoter after heat shock, whereas in B. subtilis AMY2 and B. subtilis PA2, transcription of the heterologous genes was initiated by dual promoters, the phage promoter and the native promoter. The application of dual promoters increased the productivity of both enzymes, with 133% enhancement for alpha-amylase production and 113% enhancement for penicillin acylase production.
Bacillus Phages ; genetics ; metabolism ; Bacillus subtilis ; genetics ; metabolism ; Cloning, Molecular ; Penicillin Amidase ; biosynthesis ; genetics ; Promoter Regions, Genetic ; Recombinant Proteins ; biosynthesis ; genetics ; Transformation, Bacterial ; alpha-Amylases ; biosynthesis ; genetics

AIMTo demonstrate the specific killing of folate receptor (FR)-positive tumor cells can be achieved by folate-targeted penicillin-G amidase (PGA) combined with its prodrug substrate N-(phenylacetyl) doxorubicin (DOXP).

METHODSFolic acid was covalently linked to PGA and folate content value was determined by quantitative UV spectrophotometry. The ability of folate conjugated PGA to hydrolyze DOXP was measured by RP-HPLC. Visual demonstration of uptake by FR (+) HeLa and SKOV3 cells was detected by using FITC labeled folate-PGA and a fluorescence microscopy. The cytotoxicity of DOXP towards the cells in the presence or absence of folate-PGA was assayed by using MTT method.

RESULTSThe folate-PGA has a specific activity of 29. 8 U x mg(-1) (protein). FR selectivity was confirmed by fluorescence microscopy. The combination of DOXP prodrug with folate-PGA generated higher cytotoxicity towards the FR (+) cells than free doxorubicin. The IC50 was 0.72 micromol x L(-1) for HeLa cells and 0.75 micromol x L(-1) for SKOV3 cells, respectively. Further, the enhanced cytotoxicity reduced greatly with the addition of free folic acid.

CONCLUSIONFolate conjugated PGA did not significantly compromise PGA catalytic activity and enabled binding prodrug-activating enzyme PGA to folate receptor expressing cells, and increased the sensitivity of the cells to doxorubicin followed by administration of its prodrug substrate.

Antibiotics, Antineoplastic ; pharmacology ; Carrier Proteins ; metabolism ; Cell Line, Tumor ; Doxorubicin ; analogs & derivatives ; pharmacology ; Drug Delivery Systems ; Female ; Folate Receptors, GPI-Anchored ; Folic Acid ; chemistry ; pharmacology ; HeLa Cells ; Humans ; Inhibitory Concentration 50 ; Ovarian Neoplasms ; pathology ; Penicillin Amidase ; chemistry ; pharmacology ; Prodrugs ; pharmacology ; Receptors, Cell Surface ; metabolism