Preparation of 3-deacetyl cephalosporins by Aspergillus niger lipase

Enzymatic deprotection of the cephalosporin 3'-acetoxy group using Candida antarctica lipase B

Cephalosporins remain one of the most important classes of antibiotics. A useful site for derivatization involves generation of and chemistry at the 3'-hydroxymethyl position. While 3'-acetoxymethyl-substituted cephalosporins are readily available, deacetylation to access the free 3'-hydroxymethyl group is problematic when the carboxylic acid is protected as an ester. Herein we report that this important transformation has been efficiently accomplished using Candida antarctica lipase B. Although this transformation is difficult to carry out using chemical methods, the enzymatic deacetylation has been successful on gram scale, when the cephalosporin is protected as either the benzhydryl or tert-butyl esters and on the corresponding sulfoxide and sulfone of the tert-butyl ester.

Protein immobilization on epoxy-activated thin polymer films: effect of surface wettability and enzyme loading

A series of epoxy-activated polymer films composed of poly(glycidyl methacrylate/butyl methacrylate/hydroxyethyl methacrylate) were prepared. Variation in comonomer composition allowed exploration of relationships between surface wettability and Candida antartica lipase B (CALB) binding to surfaces. By changing solvents and polymer concentrations, suitable conditions were developed for preparation by spin-coating of uniform thin films. Film roughness determined by AFM after incubation in PBS buffer for 2 days was less than 1 nm. The occurrence of single CALB molecules and CALB aggregates at surfaces was determined by AFM imaging and measurements of volume. Absolute numbers of protein monomers and multimers at surfaces were used to determine values of CALB specific activity. Increased film wettability, as the water contact angle of films increased from 420 to 550, resulted in a decreased total number of immobilized CALB molecules. With further increases in the water contact angle of films from 55 degrees to 63 degrees, there was an increased tendency of CALB molecules to form aggregates on surfaces. On all flat surfaces, two height populations, differing by more than 30%, were observed from height distribution curves. They are attributed to changes in protein conformation and/or orientation caused by protein-surface and protein-protein interactions. The fraction of molecules in these populations changed as a function of film water contact angle. The enzyme activity of immobilized films was determined by measuring CALB-catalyzed hydrolysis of p-nitrophenyl butyrate. Total enzyme specific activity decreased by decreasing film hydrophobicity.

Enzymatic Modifications of Cephalosporins by Cephalosporin Acylase and Other Enzymes

Semisynthetic cephalosporins are important antibacterials in clinical practice. Semisynthetic cephalosporins are manufactured by derivatizing 7-aminocephalosporanic acid (7-ACA) and its desacetylated form. Microbial enzymes such as D-amino acid oxidase, glutaryl-7-ACA acylase and cephalosporin esterase are being used as biocatalysts for the conversion of cephalosporin C (CEPH-C) to 7-ACA and its desacetylated derivatives. Recent developments in the field of enzymatic modifications of cephalosporin with special emphasis on group of enzymes called as cephalosporin acylase is discussed in this review. Aspects related to screening methods, isolation and purification, immobilization, molecular cloning, gene structure and expression and protein engineering of cephalosporin acylases have been covered. Topics pertaining to enzymatic modifications of cephalosporin by D-amino acid oxidase, cephalosporin methoxylase and beta-lactamase are also covered.

Properties of a thermostable extracellular lipase fromBacillus megaterium AKG-1

An extracellular lipase isolated from Bacillus megaterium AKG-1 had an optimum activity at 55 degrees C/pH 7.0. It retained 100% activity at 50 degrees C for 30 min with a half life of 30 min at 70 degrees C. A 20-70% increase in lipase activity was observed in presence of acetone (20% v/v), DMSO (20% v/v) and isopropanol (10% v/v). The enzyme activity was 92, 98 and 107% after 24 h, on treatment with 10% (v/v) acetone, benzene and isopropanol respectively. Deoxycholic acid, sodium deoxycholate, lithocholic acid, rhamnolipid, Brij 52 and cholic acid stimulated the lipase activity by 76, 36, 24, 24, 23.6 and 13%, respectively. Addition of reducing agents like sodium sulphite, sodium metabisulphite and L-cysteine-HCl, at 10 mM concentration stimulated lipase activity by 127, 146 and 150% respectively. The lipase appeared to show enantioselectivity in hydrolyzing racemic 3-acetoxy-beta-lactam as it hydrolyzed only the (+) enantiomer.

Characterization of an industrial biocatalyst: immobilized glutaryl-7-ACA acylase

A batch of the immobilized industrial biocatalyst glutaryl-7-ACA acylase (GA), one of the two enzymes involved in the biotransformation of cephalosporin C (CefC) into 7-aminocephalosporanic acid (7-ACA), was characterized. K(m) value for glutaryl-7-ACA was 5 mM. Enzyme activity was found to be optimal at pH between 7 and 9.5 and to increase with temperature and in buffered solutions. To avoid product degradation, optimal reaction conditions were obtained working at 25 degrees C using a 50-mM phosphate buffer, pH 8.0. Immobilized GA showed good stability at pH value below 9 and at temperature up to 30 degrees C. The inactivation of immobilized GA in the presence of different amounts of H(2)O(2), a side product that might be present in the plant-scale industrial solutions of glutaryl-7-ACA, was also investigated, but the deactivation rates were negligible at H(2)O(2) concentration that might be reached under operative conditions. Finally, biocatalyst performance in the complete two-step enzymatic conversion process from CefC to 7-ACA was determined on a laboratory scale. Following the complete conversion of a 75 mM solution of CefC into glutaryl-7-ACA catalyzed by an immobilized D-amino acid oxidase (DAAO), immobilized GA was used for the transformation of this intermediate into the final product 7-ACA. This reaction was repeated for 42 cycles. An estimation of the residual activity of the biocatalyst showed that 50% inactivation of immobilized GA was reached after approximately 300 cycles, corresponding to an enzyme consumption of 0.4 kU per kg of isolated 7-ACA.