Enzymes semisynthetic, synthesis

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 ... 

Unlike these nonspecific agents, mycophenolate mofetil (6.4) tends to be a lymphocyte-specific cytotoxic agent. Mycophenolate mofetil is a semisynthetic derivative of mycophe-nolic acid, isolated from the mold Penicillium glaucum. It inhibits both T and B lymphocyte action. Since it inhibits the enzyme inosine monophosphate dehydrogenase, which catalyses purine synthesis in lymphocytes, this agent has a more specific effect on lymphocytes than on other cell types. Mizoribine (6.5) is a closely related drug which inhibits nucleotide synthesis, preferentially in lymphocytes. 

Alternative methods for the synthesis of peptide aldehydes include reduction of acid halides, phenyl esters, thioesters, and anhydrides prepared from corresponding acids, isoxazolidides, and the hydrolysis of thiazolidine peptides 17,54-56 Enzymes such as thermolysin, subtilisin, and pronase E have proven valuable as effective semisynthetic alternatives 40,57 5 62 ... 

Haring D, Schueler E, Adam W, Saha-Moeller CR, Schreier P. Semisynthetic enzymes in asynunetric synthesis enantioselec-tive reduction of racemic hydroperoxides catalyzed by seleno-subtilisin. J. Org. Chem. 1999 64 832-835. 

Microorganisms including yeasts and bacteria are able to produce D-amino acid oxidases, and interest has centered particularly on the use of /7-alkane as growth substrates (Kawamoto et al. 1977). The enzyme has achieved importance for its role in carrying out the first step in the transformation of cephalosporin C to 7-aminocephalosporanic acid that is an intermediate for the synthesis of semisynthetic cephalosporins. The nucleotide sequence of the enzyme from Rhodotorula gracilis ATCC 26217 has been established and the gene could be overexpressed in Escherichia coli (Alonso et al. 1998). 

Enzymes are used as catalysts for large scale bioconversions e.g. glucose iso-merase in the high fructose corn syrup (HFCS) process 10, penicillinase in the synthesis of semisynthetic penicillins 11, as well as aminoamidase 12, 13 and ami-noacylase[14 in the production of L-amino acids. Additionally, a variety of processes for fine chemical synthesis has been developed, e. g. for amino acids, peptides and a broad spectrum of other optically active substances 15-23. ... 

The biocatalytic hydrolysis of amides and also the enzyme catalyzed formation of amides and the synthesis of (semisynthetic) antibiotics is included in this section. 

Substituted hydantoin derivatives have been used as precursors for d- and L-amino acids in chemical synthesis. However, they are hydrolyzed enantioselectively by the enzymes named hydantoinases some act specifically on D-5-substituted hydantoins, and others on the L-isomers. N-Carbamoyl amino acids formed are also hydrolyzed enantiospecifically by N-carbamoyl amino acid amidohydrolases to produce d- or l-amino acids (Fig. 17-15). Since the Kanegafuchi Chemical Industry, Japan, commercialized an enzymatic procedure for the production of D-p-hydroxyphenylglycine, which is a building block for the semisynthetic P-lactam antibiotic amoxycillin, various processes for amino acid production by means of hydantoinases have been developed 131 133. ... 

Chemferm is one of among several companies which apply penicillin acylase for the kinetically controlled industrial synthesis of semisynthetic antibiotics in aqueous environments (Scheme 37) [109-111]. Ampicillin (119) and amoxicillin (120) can be obtained by the enzyme-catalyzed condensation of 6-aminopenicillic acid (6-APA, 117) with the amide or ester of D-(-)-4-hydrox-yphenylglycine and D-(-)-phenylglycine, respectively. In a similar way, cephalexin (121) can be obtained by reaction of D-(-)-phenylglycine with 7-aminodesacetoxycephalosporanic acid (7-ADCA, 118). Penicillin acylase from diverse microbial strains such as E. colU Klyveromyces citrophiluy and Bacillus megabacterium was successfully applied for this transformation and was used in its immobilized form based on a gelatin carrier. The immobilization allows an easy separation from the reaction medium and the reuse of the enzyme for at least 50 cycles. Impressive characteristics of this transformation are yields >90%, a selectivity of >95%, and an optical purity of >99% ee. The industrial manufacture takes place in repetitive batch reactors at many locations worldwide with an annual production volume of 2,000 t. 

Recently Keyes (80-82) described an interesting approach to the synthesis of semisynthetic enzymes. A protein was partially denaturated and then brought in contact with an inhibitor of an enzyme to be modelled. 

The setting up of new biotechnology companies (Section 1.4.2) was the key event for the development of biopharmaceuticals based on recombinant technologies. Antibiotic manufacture had been established before this (Section 1.3). Antibiotics are still the most important strategy against bacterial infections. The world production of antibiotics is estimated at over 60000 tons per aimum, valued at more than 30 billion per year [128, 129]. For the synthesis of semisynthetic penicUlins and cephalosporins, the fermentation products penicillin G and cephalosporin, respectively, are hydrolyzed by immobilized enzymes to yield the acid form with the intact P-lactam ring as the active principal 6-APA, 7-ACA, or 7-aminodeacetoxy cephalosporanic acid (7-ADCA). 

Sih CJ, Chen C-S (1984) Microbial asymmetric catalysis - Enantio-selective reduction of ketones. Angew Chem Int Ed Engl 23 570-578 Slama J, Oruganti SR, Kaiser ET (1981) Semisynthetic enzymes Synthesis of a new flavopapain with high catalytic efficiency. J Am Chem Soc 103 6211-6213... 

The important pharmacological activity of many alkaloids has attracted and motivated chemists to make many derivatives of these natural compotmds. The semisynthetic preparation alkaloids has resulted in the production of drugs with improved properties, such as the addition of a 14-hydroxy group to the morphine alkaloid structure which has been found to dramatically increase its potency [92]. However, the chemical synthesis of such compounds is often difficult to achieve on a commercial scale due to the chemical complexity of the starting material, cost, and environmental issues, in addition to the limited supply of the precursors required. Biotransformation can offer a number of advantages over conventional chemical processes. The specificity of enzyme-catalyzed... 

Other milestones are grafting by radical, cationic, anionic and coordinative polymerization use of semisynthetic and synthetic polymers as ion exchange resins " and catalysts which, in some cases, mimic and even surpass the efficiency of enzymes and solid phase peptide synthesis by Merrifield and Letsinger. ... 

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