Hydrolysis of a penicillin

The penaldic acids were obtained by alkaline hydrolysis of a penicillin. Initially, this gave a dicarboxylic acid known as a penicilloic acid (3.3). Further... 

Several bacterial penicillin-binding proteins have been shown to be serine enzymes (Section 2). P-Lactamases are efficient and clinically important enzymes which play an important part in bacterial resistance to the normally lethal action of P-lactam antibiotics. A major class of P-lactamases are also serine enzymes that function by covalent catalysis with the intermediate formation of an acyl-enzyme (Knott-Hunziker et al., 1982 Cohen and Pratt, 1980 Fisher et al., 1980 Anderson and Pratt, 1983 Cartwright and Fink, 1982, Joris et al., 1984). The P-lactamase catalysed hydrolysis of a penicillin thus proceeds by formation of an acyl-enzyme which is an a-penicilloyl ester of a serine residue. The mechanism of reaction of penicillin with alcohols is therefore of obvious relevance, but in addition acyl transfer from nitrogen to oxygen nucleophiles is of current interest. 

As a simple model for the enzyme penicillinase, Tutt and Schwartz (1970, 1971) investigated the effect of cycloheptaamylose on the hydrolysis of a series of penicillins. As illustrated in Scheme III, the alkaline hydrolysis of penicillins is first-order in both substrate and hydroxide ion and proceeds with cleavage of the /3-lactam ring to produce penicilloic acid. In the presence of an excess of cycloheptaamylose, the rate of disappearance of penicillin follows saturation kinetics as the cycloheptaamylose concentration is varied. By analogy to the hydrolysis of the phenyl acetates, this saturation behavior may be explained by inclusion of the penicillin side chain (the R group) within the cycloheptaamylose cavity prior to nucleophilic attack by a cycloheptaamylose alkoxide ion at the /3-lactam carbonyl. The presence of a covalent intermediate on the reaction pathway, although not isolated, was implicated by the observation that the rate of disappearance of penicillin is always greater than the rate of appearance of free penicilloic acid. 

The efficacy of penicillin-type antibiotics is constrained by the ability of bacteria to induce enzymes for their destruction. In relation to this problem, Page and coworkers (Buckwell et al., 1988a,b) have studied the hydrolysis of acylated penicillins [55] and cephalosporins [56] catalysed by a bacterial /3-lactamase (Tables A6.9 and A6.10). It is noteworthy that the two series of substrates show quite different responses to changes in the length of the acyl side chain (C2 to C12). For the penicillins, which are cleaved much more efficiently, there is a broad maximum in the kinetic parameters around C5 to C7, whereas for the cephalosporins there is a linear increase in kc/KM and... 

Phenylacetic acid produced by hydrolysis of the penicillin G can be recycled and fed back as a precursor into the Penicillium fermentation. 

It is a monothiol, prepared by alkaline hydrolysis of benzyl penicillin and chemically it is beta-dimethylcysteine. 

The two largest scale industrial processes utilising immobilised enzymes are the hydrolysis of benzyl penicillin by penicillin acylase and the isomerisation of glucose to a glucose-fructose mixture by immobilised glucose isomerase. The immobilisation techniques used in general may be broadly categorised as ... 

A number of interesting studies of lactam hydrolysis have been published. The metal(II)-catalyzed hydrolysis of some penicillin and cephalosporin derivatives displays saturation kinetics.410"412 A 1 1 complex is formed between the metal ion and penicillin which undergoes base hydrolysis up to 10s times faster than the free ligand. The catalytic activity follows the order Cu,>ZnII>NiII = Co11. Coordination of penicillin to copper(II) is believed to occur via the /3-lactam nitrogen and the carboxylate group (121)4l0-4n but other sites have been proposed.413... 

Amoxicillin (21) is a semi-synthetic penicillin antibiotic. The penicillin portion is derived from fermentation of either penicillin-V or penicillin-G, and then the sidechain is removed to afford 6-APA. This transformation can be done chemically.69 207 The alternative, which is growing in importance, is to perform an enzymatic cleavage under mild conditions.208 The D-p-hydroxyphenylglycine is then attached as the new sidechain chemical and enzymatic methods are available to achieve this (Scheme 31.16).209 215 The phenylglycine amino acid is obtained by a resolution (Chapters 2, 7, and 25) or by enzymatic hydrolysis of a hydantoin (Chapter 2, 6, and 19).216-220... 

Thomas and Broadbridge 28 have developed a low-voltage electrophoresis method for the rapid separation of a penicillin from its penicilloic acid. Phenoxymethyl penicillin was one of 12 penicillins studied. The method was found to be particularly useful for rabbit sera and urine and the products of bacterial hydrolysis... 

Two fragments were isolated by hydrolysis of the penicillins with acid. The first, penicillamine (3.2), was identified as p,p-dimethylcysteine by synthesis and shown to possess the unusual o-amino acid configuration. The second fragment, which retained the side-chain, was known as a penaldic acid (3.4). It behaved as a p-keto acid and lost carbon dioxide to give a penilloaldehyde... 

Novella IS, Fargues C, GreviUot G (1994) Improvement of extraction of penicillin acylase by a combined use of chemical methods. Biotechnol Bioeng 44 379-382 Ospina S, Lopez-Mungufa A, GonztQez R et al. (1992) Characterization and use of a penicillin acylase biocatalyst. J. Chem Technol Biotechnol 53 205-214 Ospina SS, Merino E, Ramirez OT et til. (1995) Recombinant whole cell penicillin acylase biocatalyst production, characterization and use in the synthesis and hydrolysis of antibiotics. Biotechnol Lett 17 615-620... 

Overview Waldmann and his group recently reported the development of a penicillin G acylase sensitive safety catch linker for the attachment of alcohols and anilines to a polymeric support (Fig. 6) (20). The release of the synthesized target molecule from the support is initiated by the hydrolysis of the phenylacetamide moiety contained in the linker 28 under extremely mild conditions (pH 7.0, room temperature or 37°C). The liberated benzylamine 29 intermediate cyclizes instantaneously to release the desired target molecule with the tetrahydroisoquinolinone 30 formed in the course of this process remaining on the polymer. 

The second example, which is also in daily use, is the specific hydrolysis of natural penicillin G by penicillin amidase in preparative scale, again through a chromatographic process (129). It produces a clean hydrolytic product (6-aminopenicillanic acid) free of possible contaminant and it can then be used to prepare chemically all kinds of semisynthetic penicillin derivatives. Unlike the rather unstable soluble enzyme, the insolubilized preparation shows no loss activity after up to 11 weeks of continuous operation at 37°C. Furthermore, the procedure is free from potentially allergy-inducing contaminants. 

Elucidation of the structure of the penicillin nucleus involved extensive degradation studies and X-ray analysis. Reaction of a penicillin under hydrolytic conditions followed by further degradation with mercuric chloride was shown to give D-penicillamine (46) and the penilloaldehyde (47). From this evidence it was concluded that the primary hydrolysis... 

The observation on GA-catalyzed hydrolysis is in contrast to the GB catalysis seen in the buffer-catalyzed hydrolysis of P-lactams of penicillins. " Thus, the probable mechanism of buffer catalysis in this case involves SA-nucleophilic catalysis (Scheme 2.44). The evidence for this catalytic proposal comes from the following observations (1) the mixed acid anhydride intermediate (Intn) has been trapped with aniline to give acetanilide as identified by HPLC (2) the kinetic runs for hydrolysis of A-benzyl-P-snltam in acetate buffers revealed biphasic plots of observed absorbance vs. reaction time an initial exponential bnrst of UV... 

APA may be either obtained directly from special Penicillium strains or by hydrolysis of penicillin Q with the aid of amidase enzymes. A major problem in the synthesis of different amides from 6-APA is the acid- and base-sensitivity of its -lactam ring which is usually very unstable outside of the pH range from 3 to 6. One synthesis of ampidllin applies the condensation of 6-APA with a mixed anhydride of N-protected phenylglydne. Catalytic hydrogenation removes the N-protecting group. Yields are low (2 30%) (without scheme). 

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