Formation by enzymatic hydrolysis

Steam treatment of an industrial process stream, denoted starch-free wheat fiber, was investigated to improve the formation of monomeric sugars in subsequent enzymatic hydrolysis for further bioconversion into ethanol. The solid fraction in the process stream, derived from a combined starch and ethanol factory, was rich in arabinose (21.1%), xylose (30.1%), and glucose (18.6%), in the form of polysaccharides. Various conditions of steam pretreatment (170-220°C for 5-30 min) were evaluated, and their effect was assessed by enzymatic hydrolysis with 2 g of Celluclast + Ultraflo mixture/ 100 g of starch-free fiber (SFF) slurry at 5% dry matter (DM). The highest overall sugar yield for the combined steam pretreatment and enzymatic hydrolysis, 52 g/100 g of DM of SFF, corresponding to 74% of the theoretical, was achieved with pretreatment at 190°C for 10 min followed by enzymatic hydrolysis. 

EME and BEG, which is mainly obtained by enzymatic hydrolysis, represents respectively the 32-49 % and 29 45 % of total urinary metabolites cocaine can be converted, in small amounts, to norcocaine (NCOC) and psychoactive metabolite norbenzoylecgonine (NBE). The combined intake of alcohol and cocaine determines the formation of a pharmacologically active metabolite, the cocaethylene (ethyl ester of benzoylecgonine, CE), with a significant liver toxicity [13],... 

Pyrethroids are commercially important insecticides that usually contain a cyclopropyl unit that is m-substituted and a cyanohydrin derivative. They are usually sold as a mixture of isomers. However, asymmetric routes have been developed, especially because these compounds are related to chrysanthemic esters (Chapter 12).251 The pyrethroids can be resolved through salt formation or by enzymatic hydrolysis.252... 

The first step in the formation of the leukotrienes is cleavage of arachidonic add from membrane phospholipids. 5-I.ipoxygcnasp, which is a calcium-dependent enzyme, catalyzes the introductionof Oi into the arachidonic add and the conversion of the resulting hydroperoxide to an epoxide. Leukotriene A, contains an epoxide group. Leukobiene (LTA ) can be converted to leukotriene B (LTB4) by enzymatic hydrolysis. LTB is a dihydroxy fatty acid it regulates the functions... 

Roche D, Prasad K, Repic O (1999) Enantioselective acylation of 3-aminoesters using penicillin G acylase in organic solvents. Tetrahed Lett 40 3665-3668 Rolinson GN, Batchelor ER, Butterworth D et al. (1960) Formation of 6-aminopenicillanic acid from penicillin by enzymatic hydrolysis. Nat Lond 187 236-237 Rolinson GN, Geddes AM (2007) The 50th anniversary of the discovery of 6-aminopenicillanic acid (6-APA). Internatl J Antimicrob Agents 29 3-8 Resell CM, Ferndndez-Lafuente R, Guisdn JM (1993) Resolution of racemic mixtures by synthesis reactions catalyzed by immobilized derivatives of the enzyme peniciUin G acylase. J Mol Catal 84 365-371... 

It has been shown that inactivation of pristinamycin IIa by a plasmid-mediated resistant strain of Staphylococcus aureus, which was able to produce an acetyl transferase, occurred as a result of enzymatic acetylation of the allylic hydroxy group [19, 20]. The same resistant strain of Staphylococcus aureus was also demonstrated [21] to be capable of inactivating pristinamycin Ia by enzymatic hydrolysis of the ester bond in the macrocycle leading to formation of the linear hexapeptide, which although still capable of tight binding to the ribosome was antibacterially inactive. 

In most recent studies, new processes have been tried out to produce starch nanoparticles by (i) precipitation of amorphous starch by Ma et al and Tan et al. (ii) combining complex formation and enzymatic hydrolysis by Kim and Lim, yielding nanocrystals i.e. complexed with lipids), and... 

Microperoxidase 8 is a heme octapeptide, obtained by enzymatic hydrolysis of heart Cytochrome c, in which a histidine is axially co-ordinated to the heme iron, and acts as a fifth ligand. It exhibits two kinds of activities a peroxidase-like activity and a cytochrome P45o-like activity. Ricoux et al. (2000) have shown that microperoxidase 8 is not only able to oxidise various aliphatic and aromatic hydroxyl-amines with the formation of microperoxidase 8-Fe(II)-nitrosoalkane or -arene complexes absorbing around 414 nm, but also that these complexes can be obtained by reduction of nitroalkanes. 

Penicillins and cephalosporins are antibiotics (E 5.2) used in medicine. They inhibit cell wall formation in bacteria. The naturally occurring penicillins and cephalosporins are inactivated, e.g., by bacterial j8-lactamases and by the acid in the stomach. 6-Aminqpenicillanic acid obtained by enzymatic hydrolysis of penicillin G, is commercially converted to semi-synthetic penicillins which are stable to acids and/or resistant to penicillin-j8-lactamase and may possess a broader spectrum of antibiotic activity in comparison to the naturally occurring penicillins. Also semisynthetical cephalosporin C derivatives are used in medicine. 

The enzymatic hydroxylations play a crucial role in detoxification and excretion of toxic arenes and in drug metabolism. The enzymatic degradation of aromatics occurs via two different pathways (i) monooxygenase-mediated formation of arene oxide followed by enzymatic hydrolysis to yield tram-l,2-dio and its further metabolism and (ii) dioxygenase-catalyzed arene cis-dihydroxylation... 

Rolinson, G. N., F. R. Batchelor, D. Butterworth, J. Cameron-Wood, M. Cole, G. C. Eustace, M. V. Hart, M. Richards, and E. B. Chain Formation of 6-Aminopenicillanic Acid from Penicillin by Enzymatic Hydrolysis Nature 187, 236... 

Hydrolysis of Nitriles. The chemical hydrolysis of nitriles to acids takes place only under strong acidic or basic conditions and may be accompanied by formation of unwanted and sometimes toxic by-products. Enzymatic hydrolysis of nitriles by nitrile hydratases, nittilases, and amidases is often advantageous since amides or acids can be produced under very mild conditions and in a stereo- or regioselective manner (114,115). 

Table 3. (R)-Cyanohydrins by Enzymatic Formation from Ketones and Hydrocvamic Acid as well as (7 )-a-Hydroxy-a-methyl Carboxylic Acids by Hydrolysis...

The main application of the enzymatic hydrolysis of the amide bond is the en-antioselective synthesis of amino acids [4,97]. Acylases (EC 3.5.1.n) catalyze the hydrolysis of the N-acyl groups of a broad range of amino acid derivatives. They accept several acyl groups (acetyl, chloroacetyl, formyl, and carbamoyl) but they require a free a-carboxyl group. In general, acylases are selective for i-amino acids, but d-selective acylase have been reported. The kinetic resolution of amino acids by acylase-catalyzed hydrolysis is a well-established process [4]. The in situ racemization of the substrate in the presence of a racemase converts the process into a DKR. Alternatively, the remaining enantiomer of the N-acyl amino acid can be isolated and racemized via the formation of an oxazolone, as shown in Figure 6.34. 

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