Acylases penicillin acylase

D-amino acid oxidase glutaric acid acylase Penicillin acylase... 

Table 2. Typical Operating Parameters for Immobilized Glucose Isomerase and Penicillin V Acylase...

Immobilized enzyme Glucose isomerase Penicillin V acylase... 

The second most important group of immobilized enzymes is stiU the penicillin G and V acylases. These are used in the pharmaceutical industry to make the intermediate 6-aminopenici11anic acid [551-16-6] (6-APA), which in turn is used to manufacture semisynthetic penicillins, in particular ampicilHn [69-53-4] and amoxicillin [26787-78-0]. This is a remarkable example of how a complex chemical synthesis can be replaced with a simple enzymatic one ... 

En2yme techniques are primarily developed for commercial reasons, and so information about immobilisation and process conditions is usually Limited. A commercially available immobilised penicillin V acylase is made by glutaraldehyde cross-linking of a cell homogenate. It can be used ia batch stirred tank or recycled packed-bed reactors with typical operating parameters as iadicated ia Table 2 (38). Further development may lead to the creation of acylases and processes that can also be used for attaching side chains by ensymatic synthesis. 

This amide, readily formed from an amine and the anhydride, is readily cleaved by penicillin acylase (pH 8.1, A -methylpyrrolidone, 65-95% yield). This depro-tection procedure works on peptides as well as on nonpeptide substrates. 

This ester is conveniently formed from a penicillinic acid with PhCH2C02CH2Cl and TEA. Cleavage is accomplished by enzymatic hydrolysis with penicillin G. acylase in 70-90% yield. 

Penicillin G. acylase, pH 7.8 buffer, 35°, 30 min to 2 h. These conditions result in isolation of the disulfide, but if j8-mercaptoethanol is included in the reaction mixture, the thiol can be isolated. ... 

Preparation of PhAcOZ amino acids proceeds from the chloroformate, and cleavage is accomplished enzymatically with penicillin G acylase (pH 7 phosphate buffer, 25°, NaHS03, 40-88% yield). In a related approach, the 4-ace-toxy derivative is used, but in this case deprotection is achieved using the lipase, acetyl esterase, from oranges (pH 7, NaCl buffer, 45°, 57-70% yield). 

This amide, readily formed from an amine and the anhydride or enzymatically using penicillin amidase, is readily cleaved by penicillin acylase (pH 8.1, A -methylpyrrolidone, 65-95% yield). This deprotection procedure works on peptides, phosphorylated peptides, and oligonucleotides, as well as on nonpeptide substrates. The deprotection of racemic phenylacetamides with penicillin acylase can result in enantiomer enrichment of the cleaved amine and the remaining amide. An immobilized form of penicillin G acylase has been developed. ... 

Figure 6.11 Hydrolysis of penicillin G by penicillin acylase and p-lactamase.

Table 6.3 Some sources of penicillin acylases used for the large scale production of 6-APA.

The most commonly used source of penicillin V acylase is the fungus Bovista plumbia. Incubation of phenoxymethyl penicillin (penicillin V) with this enzyme produces a yield of about 90-92% 6-APA. 

The latter two points usually tip the balance in favour of using purified enzymes. Ideally the enzyme should be easy to isolate. The penicillin acylase from Bacillus megaterium is, for example, an extracelluar enzyme and can be readily absorbed into bentonite. 

In section 6.6.1, we described how enzymatic methods have come to dominate the production of the important intermediates used in the manufacture of semi-synthetic -lactams. In principle, the hydrolytic penicillin acylases may be used in the reverse direction to add acyl groups to 6-APA. For example, a two-step enzymatic process has been described for the preparation of ampiciilin (D-(-)-a-aminobenzylpenidllin structure shown in Figure 6.17). 

In this process, penicillin G is first hydrolysed to 6-APA with the acylase derived from Kluyvera citwphila at a slightly alkaline pH (pH 75). Subsequently the 6-APA is incubated with an acylase derived from Pseudomonas mdanogenum and with DL-phenylglydne methyl ester at pH 55. This produces ampiciilin in reasonable yields only because of the specificity of the P. melanogenum enzyme. This enzyme does not react with penicillin G nor phenylacetic acid. 

It was almost immediately recognised that the deacylated product, 7-aminocephalosporanic add (7-ACA, Figure 6.16), would be of similar importance as was 6-APA in the development of new penidllins. However, 7-ACA, the cephalosporin equivalent of 6-APA, could not be found in fermentations of Cephalosporin acremonium. In Figure 6.15 we have shown that penicillin acylase hydrolyses the acyl residue from natural cephalosporins. Up to a point this is true. These acylases will, however, only work with a limited range of acyl residues. It now seems that nature does not provide for acylases or transacylases that have the capacity to remove or change the D-a-aminoadipyl side chain of cephalosporin C efficiently in a single step. Widespread search for such an enzyme still remains unsuccessful. 

Penicillin G acylase (PGA, EC 3.5.1.11, penicillin G amidase) catalyzes the hydrolysis of the phenylacetyl side chain of penicillin to give 6-aminopenicillanic acid. PGA accepts only phenylacetyl and structurally similar groups (phenoxyacetyl, 4-pyridylacetyl) in the acyl moiety of the substrates, whereas a wide range of structures are tolerated in the amine part [100]. A representative selection of amide substrates, which have been hydrolyzed in a highly selective fashion, is depicted in Figure 6.36. 

Figure 6.36 Examples of amides resolved by penicillin C acylase-catalyzed hydrolysis (the fast-reacting enantiomer is shown).

PSL, AMANO) has been found to catalyze the Markovnikov-type addition of thiols to vinyl esters (Scheme 5.23) [114] and acylases aminoacylase [115], penicillin G acylase [116], and acylase from AspergiUus oryzae [117], the same kind of addition of various nitrogen nucleophiles. Unfortunately, most additions described above are nonstereoselective. 

Recommended model particle systems are enzymes immobilised on carriers ([27,44,45,47,49]), oil/water/surfactant or solvent/water/surfactant emulsions ([27, 44, 45] or [71, 72]) and a certain clay/polymer floccular system ([27, 42-52]), which have proved suitable in numerous tests. The enzyme resin described in [27,44,47] (acylase immobilised on an ion-exchanger) is used on an industrial scale for the cleavage of Penicillin G and is therefore also a biological material system. In Table 3 are given some data to model particle systems. 

Fig. 27. Activity loss a/a of Acylase enzym resign with the reaction time t of the enzymatic deaccylation of Penicillin G to 6-Aminopenicillanic acid (reactor design see Fig. 28)...

A seeond method of producing 6-APA came with the diseovery that certain mieroorganisms produee enzymes, penicillin amidases (acylases), which catalyse the removal of the side ehain fiom benzylpenicillin (Fig. 5. IB). 

Stereoselective hydrolysis of racemic l-(//-phenylacetylamino) alkanephos-phonic acids performed in the presence of penicillin acylase under the kinetic resolution conditions gave both the unreacted substrates and the products - the corresponding 1-aminophosphonic acids in high yields and with full enantioselec-tivity. The unreacted A -acyl derivatives were hydrolysed chemically and in this way each enantiomer of the free acid was obtained (Scheme 5). ... 

Patent literature reports on the analogous resolutions of phosphinotricin using, among others, penicillin G-acylase, penicillin G-amidase, subtilisin or microorganisms such as Enterobacter aerogenes, Klebsiella oxytoca, Corynebac-terium sp., Rhodococcus rubropertinctus and others7°... 

The above two processes employ isolated enzymes - penicillin G acylase and thermolysin, respectively - and the key to their success was an efficient production of the enzyme. In the past this was often an insurmountable obstacle to commercialization, but the advent of recombinant DNA technology has changed this situation dramatically. Using this workhorse of modern biotechnology most enzymes can be expressed in a suitable microbial host, which enables their efficient production. As with chemical catalysts another key to success often is the development of a suitable immobilization method, which allows for efficient recovery and recycling of the biocatalyst. 

Rasor and Tischer (1998) have brought out the advantages of enzyme immobilization. Examples of penicillin-G to 6-APA, hydrolysis of cephalospwrin C into 7-ACA, hydrolysis of isosorbide diacetate and hydrolysis of 5-(4-hydroxy phenyl) hydantom are cited. De Vroom (1998) has reported covalent attachment of penicillin acylase (EC 3.51.11) from E.Coli in a gelatine-based carrier to give a water insoluble catalyst assemblase which can be recycled many times, and is suitable for the production of semi-synthetic antibiotics in an aqueous environment. The enzyme can be applied both in a hydrolytic fashion and a synthetic fashion. 6-APA was produced from penicillin-G similarly, 7-ADCA was produced from desa acetoxycephalosporin G, a ring expansion product of penicillin G. 

Chong, A.S.M. and Zhao, X.S. (2004) Design of large-pore mesoporous materials for immobilization of penicillin G acylase biocatalyst. Catalysis Today, 93-95, 293-299. 

Calcined [MgAl] LDH was also used to adsorb penicillin G acylase [121]. The calcined LDH phases have porous structures, large specific surface areas and abundant basic sites to bind the enzymes. The effect of varying the composition of the LDH precursor and calcination temperature on the activity of the immobilized enzyme has been reported. In this case, the percentage of immobilized proteins increases up to 88 %. 

A more sophisticated method was developed by Ren et al. [123] for the immobilization of penicillin G acylase by covalent grafting in the interlayer galleries of a LDH by a three-step procedure using a glutamate pillared LDH as the starting material. 

---