Immobilized penicillinacylase: Application to the synthesis of the dipeptide aspartame

Purification and partial characterization of novel penicillin V acylase from Acinetobacter sp. AP24 isolated from Loktak Lake, an Indo-Burma biodiversity hotspot

Members of the bacterial genus Acinetobacter have attracted great attention over the past few decades, on account of their various biotechnological applications and clinical implications. In this study, we are reporting the first experimental penicillin V acylase (PVA) activity from this genus. Penicillin acylases are pharmaceutically important enzymes widely used in the synthesis of semisynthetic beta-lactam antibiotics. The bacterium, identified as Acinetobacter sp. AP24, was isolated from the water of Loktak Lake (Manipur, India), an Indo-Burma biodiversity hotspot. PVA production was increased threefold in an optimized medium with 0.2% sodium glutamate and 1% glucose as nitrogen and carbon sources respectively, after 24 hr of fermentation at 28°C and pH 7.0 with shaking at 180 rpm. The enzyme was purified to homogeneity by cation-exchange chromatography using SP-sepharose resin. The PVA is a homotetramer with subunit molecular mass of 34 kD. The enzyme was highly specific toward penicillin V with optimal hydrolytic activity at 40°C and pH 7.5. The enzyme was stable from pH 5.0 to 9.0 at 25 °C for 2 hr. The enzyme retained 75% activity after 1 hr of incubation at 40°C at pH 7.5.

Sequence and structure-based comparative analysis to assess, identify and improve the thermostability of penicillin G acylases

Penicillin acylases are enzymes employed by the pharmaceutical industry for the manufacture of semi-synthetic penicillins. There is a continuous demand for thermostable and alkalophilic enzymes in such applications. We have carried out a computational analysis of known penicillin G acylases (PGAs) in terms of their thermostable nature using various protein-stabilizing factors. While the presence of disulfide bridges was considered initially to screen putative thermostable PGAs from the database, various other factors such as high arginine to lysine ratio, less content of thermolabile amino acids, presence of proline in β-turns, more number of ion-pair and other non-bonded interactions were also considered for comparison. A modified consensus approach designed could further identify stabilizing residue positions by site-specific comparison between mesostable and thermostable PGAs. A most likely thermostable enzyme identified from the analysis was PGA from Paracoccus denitrificans (PdPGA). This was cloned, expressed and tested for its thermostable nature using biochemical and biophysical experiments. The consensus site-specific sequence-based approach predicted PdPGA to be more thermostable than Escherichia coli PGA, but not as thermostable as the PGA from Achromobacter xylosoxidans. Experimental data showed that PdPGA was comparatively less thermostable than Achromobacter xylosoxidans PGA, although thermostability factors favored a much higher stability. Despite being mesostable, PdPGA being active and stable at alkaline pH is an advantage. Finally, several residue positions could be identified in PdPGA, which upon mutation selectively could improve the thermostability of the enzyme.

Enzymatic Synthesis of β-Lactam Antibiotics andN-Fatty-Acylated Amino Compounds by the Acyl-Transfer Reaction Catalyzed by Penicillin V Acylase fromStreptomyces mobaraensis

Penicillin V acylase from Streptomyces mobaraensis (Sm-PVA) showed high acyl-transfer activity in reactions using methyl esters of carboxylic acid (acyl donor) and amino compounds (nucleophile), to produce the corresponding amides. Moreover, Sm-PVA had broad substrate specificity, as indicated by the fact that it catalyzed the efficient synthesis of beta-lactam antibiotics, capsaicin derivatives, and N-fatty-acyl-amino acid/N-fatty-acyl-peptide derivatives.

Mutant Escherichia coli penicillin acylase with enhanced stability at alkaline pH

Increased stability at alkaline pH should be a valuable attribute for the utilization of penicillin acylase in bioreactors employed to convert penicillins into 6-aminopenicillanic acid, a precursor of semisynthetic penicillins. In these systems, base is added for pH control, which results in local alkaline conditions that promote enzyme inactivation. Hydrolysis and synthesis reactions are also pH dependent. Here, we report work in which the gene coding for Escherichia coli penicillin acylase was subjected to oligonucleotide-directed random mutagenesis at regions coding for amino acids predicted to be at the surface of the enzyme. The resulting mutant library, cloned in E. coli, was screened by a filter paper assay of the colonies for the presence of penicillin acylase activity with enhanced stability at alkaline pH. Characterization of one of the selected clones revealed the presence of a mutation, Trp431-Arg, which would presumably alter the surface charge of the protein. In vitro experiments demonstrated a near twofold increase in the half-life of the mutant enzyme when stored at pH 8.5 as compared with the wild-type enzyme, with a comparable specific activity at several pH values. In general, the mutant displayed increased stability toward the basic side in the pH-stability profile. (c) 1995 John Wiley & Sons, Inc.

The use of Fmoc-Lys(Pac)-OH and penicillin G acylase in the preparation of novel semisynthetic insulin analogs

In this paper, we present the detailed synthetic protocol and characterization of Fmoc-Lys(Pac)-OH, its use for the preparation of octapeptides H-Gly-Phe-Tyr-N-MePhe-Thr-Lys(Pac)-Pro-Thr-OH and H-Gly-Phe-Phe-His-Thr-Pro-Lys(Pac)-Thr-OH by solid-phase synthesis, trypsin-catalyzed condensation of these octapeptides with desoctapeptide(B23-B30)-insulin, and penicillin G acylase catalyzed cleavage of phenylacetyl (Pac) group from Nepsilon-amino group of lysine to give novel insulin analogs [TyrB25, N-MePheB26,LysB28,ProB29]-insulin and [HisB26]-insulin. These new analogs display 4 and 78% binding affinity respectively to insulin receptor in rat adipose membranes.

Use of enzyme penicillin acylase in selective amidation/amide hydrolysis to resolve ethyl 3-amino-4-pentynoate isomers

The beta-amino acid, (S)-ethyl-3-amino-4-pentynoate, is a chiral synthon used in the synthesis of xemilofiban hydrochloride, an anti-platelet agent. A biocatalytic approach was developed to resolve (R)- and (S)-enantiomers of ethyl 3-amino-4-pentynoate in enantiomerically pure form employing the enzyme Penicillin acylase. In the acylation, phenylacetic acid was used as an acylating agent. We have shown that both the acylation and deacylation can be employed and that the activity of the enzyme Penicillin acylase can be controlled by maintaining an appropriate pH of the reaction medium.

Penicillin Acylase-Mediated Synthesis of 2-Acetyl-1-pyrroline and of 2-Propionyl-1-pyrroline, Key Roast-Smelling Odorants in Food. Inclusion Complexes with beta-Cyclodextrin and Their NMR and MS Characterization

The synthesis of the strong natural roast odorants 1 and 2 is achieved from the C-6 isomeric alcohols 16 and 21 via the acetylenic C-6 and C-7 amines 8 and 9. Key step in the process is the hydrolysis of the N-phenylacetamides 12 and 13 by means of immobilized penicillin acylase, which affords the 1-amino-4,5-diketones 14 and 15, spontaneously ring closing to 1 and 2. These latter compounds form inclusion complexes with beta-cyclodextrin, as demonstrated by NMR measurements in deuterated water and FAB-MS spectra.

Hydrolysis of peptide esters by different enzymes

The combined use in peptide synthesis of the Fmoc-group with methyl, benzyl or p-nitro benzyl esters is not practical because of the elimination of the Fmoc-group under basic conditions and by catalytic hydrogenation. Nevertheless the solution synthesis of peptides requires those combinations in some cases. For this purpose we have investigated enzymatic hydrolysis of some tri and tetrapeptide esters. The hydrolysis were carried out under pH-control. We measured deprotection of the carboxyl group by thermitase, porcine liver esterase, carboxypeptidase A and alpha-chymotrypsin. The main problems are to suppress proteolytic degradation of the peptide bond and to bring the protected peptides into solution. To solve both problems we used dimethylformamide and dimethylsulfoxide as cosolvents. The ratios between esterolytic and proteolytic activity were estimated under various cosolvent concentrations. Advantages of this method are to avoid side reactions of alkaline instable side chains (e.g. asparagine, glutamine), cleavage of base labile protecting groups and racemization by alkaline saponification. The enzymatic deprotection was followed by HPLC, HPTLC and titration. On a preparative scale this method gives good yields and sufficiently pure products.

Penicillin acylase-catalyzed protection and deprotection of amino groups as a promising approach in enzymatic peptide synthesis

Penicillin acylase from E. coli is able to catalyze both the introduction and the removal of the phenylacetyl group. We have established that phenylacetyl derivatives of amino acids and peptides can be used in protease-catalyzed peptide synthesis. Here the synthesis of leucine-enkephalin using enzymes for N-terminal amino group protection, peptide bond formation and deprotection is described.

Immobilization-stabilization of penicillin G acylase from Escherichia coli

We have developed a strategy for immobilization-stabilization of penicillin G acylase from E. coli, PGA, by multipoint covalent attachment to agarose (aldehyde) gels. We hve studied the role of three main variables that control the intensity of these enzyme-support multiinteraction processes: 1. surface density of aldehyde groups in the activated support; 2. temperature; and 3. contact-time between the immobilized enzyme and the activated support prior to borohydride reduction of the derivatives. Different combinations of these three variables have been tested to prepare a number of PGA-agarose derivatives. All these derivatives preserve 100% of catalytic activity corresponding to the soluble enzyme that has been immobilized but they show very different stability. The less stable derivative has exactly the same thermal stability of soluble penicillin G acylase and the most stable one is approximately 1,400 fold more stable. A similar increase in the stability of the enzyme against the deleterious effect of organic solvents was also observed. On the other hand, the agarose aldehyde gels present a very great capacity to immobilize enzymes through multipoint covalent attachment. In this way, we have been able to prepare very active and very stable PGA derivatives containing up to 200 International Units of catalytic activity per mL. of derivative with 100% yields in the overall immobilization procedure.