Pen G acylase

Enzyme resin Pen G-Acylase immobilized on 60 240- 150 1080 8-3 Enzyme activity Enzyme test... 

As an example the deactivation of immobilised Pen G acylase, which catalyses the reaction of Pen G to 6-Aminopenicillanic acid and Phenylacetic acid, was studied. This enzyme was covalently bound on an ion-exchanger and cross-linked by glutaric aldehyde. To maintain a high reaction velocity, a neutral pH value (removal of Phenylacetic acid) and therefore the supply of NaOH and stirring for distribution of the base are required. 

Lactams, i.e., penicillins and cephalosporins, represent the most important class of antibiotics. Penicillins consist of a common core, 6-aminopenicillanic acid (6-APA) and different side chains. Penicillin G (pen G), with a phenyl acetate side chain, and penicillin V (pen V), with a phenoxyacetate side chain, are fermented from the fungus Penicillium chrysogenum all the others are produced from 6-APA, which nowadays is produced mostly from pen G via penicillin G amidase (pen G amidase, pen G acylase, PGA, E.C. 3.5.1.11 Figure 7.33). Cephalosporins feature 7-aminocephalosporanic acid (7-ACA) or its deacetyl-form, 7-aminodesacetyl-cephalosporanic add (7-ADCA) as their common core cephalosporin C (Ceph C) is obtained through fermentation, and all the others are derived from 7-A(D)CA. 

Figure 7.35 Pen G acylase in the process to semi-synthetic /2-lactam antibiotics (Drauz, 2002).

In Chapter 7, Section 7.5.1, we covered the use of pen G acylase (PGA) for the catalysis of condensation reactions in the synthesis of /J-lactam antibiotics. The same principle is applied in the commercial route to Loracarbef from Eli Lilly (Indianapolis/IN, USA) (Figure 13.31). Instead of 6-APA, the nucleophile is cis-3-aminoazetidinone, importantly substituted in the 4-position by a 2 -furylethyl group the electrophile is methyl phenoxyacetate. Pen G acylase from E. coli does not hydrolyze the phenoxyacetyl ester of the pen V side chain but condenses the ester with the nucleophile to the (2P,3S)-/3-lactam intermediate with 44% conversion and 97% e.e. (Briggs, 1994). 

The /3-amino add (S)-ethyl-3-amino-4-pentynoate is a chiral synthon used in the synthesis of xemilofiban hydrochloride, an anti-platelet agent. (R)- and (S)-enanti-omers of ethyl 3-amino-4-pentynoate were obtained in enantiomerically pure form by employing penicillin acylase (Pen G acylase, PGA, Chapter 7, Section 7.5.1) (Figure 13.32) (Topgi, 1999). Both the acylation and deacylation modes were ap-... 

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