Enzymatic hydrolysis structure

A synthesis of the important biosynthetic intermediate mevalonic acid starts with the enzymatic hydrolysis of the diester A by pig liver esterase. The pro-R group is selectively hydrolyzed. Draw a three-dimensional structure of the product. 

A certain polypeptide is shown by arid hydrolysis to contain only three amino acids serine(Ser), alanine(Ala), and methionine(Met) with mole fractions of j, and respectively. Enzymatic hydrolysis yields the following fragments Ser-Ala Ser-Met Ala-Ser. Deduce the primary structure of the polypeptide. 

Buchwald P. Structure-metabolism relationships steric effects and the enzymatic hydrolysis of carboxylic esters. Mini Rev Med Chem 2001 1 101-11. 

Soft fi-blockers have a particular therapeutic role to play, accounting for the amount of attention they have received. For example, a comprehensive study of ca. 80 analogues of general structure 7.64 has established the in vitro and in vivo activity of many of these compounds and confirmed that their enzymatic hydrolysis is highly sensitive to structural effects [137]. Here, the labile moiety is incorporated into the side chain, with the consequence that hydrolysis destroys the pharmacophore. 

P. Buchwald, N. Bodor, Quantitative Structure-Metabolism Relationships Steric and Nonsteric Effects in the Enzymatic Hydrolysis of Noncongeneric Carboxylic Esters , J. Med. Chem. 1999, 42, 5160-5168. 

Higher homologues of glycine have also been evaluated as pro-moieties of active alcohols or phenols. Thus, the highly lipophilic a-tocopherol was de-rivatized with a series of m-aminoalkanecarboxylic acids in the search for a water-soluble, injectable provitamin E [146], Good to high water solubility was indeed achieved. The esters were substrates of liver esterases and showed marked structure-dependent differences in their rate of enzymatic hydrolysis. 

By forming intramolecular and intermolecular hydrogen bonds between OH groups within the same cellulose chain and the surrounding cellulose chains, the chains tend to be arranged in parallel and form a crystalline supermolecular stracture. Then, bundles of linear cellulose chains (in the longitudinal direction) form a microfibril which is oriented in the cell wall structure. Cellulose is insoluble in most solvents and has a low accessibility to acid and enzymatic hydrolysis (Demirbas, 2008b). 

The above-mentioned facts have important consequences on the stereochemical outcome of the kinetic resolution of asymmetrically substituted epoxides. In the majority of kinetic resolutions of esters (e.g. by ester hydrolysis and synthesis using lipases, esterases and proteases) the absolute configuration at the stereogenic centre(s) always remains the same throughout the reaction. In contrast, the enzymatic hydrolysis of epoxides may take place via attack on either carbon of the oxirane ring (Scheme 7) and it is the structure of the substrate and of the enzyme involved which determine the regioselec-tivity of the attack [53, 58-611. As a consequence, the absolute configuration of both the product and substrate from a kinetic resolution of a racemic... 

Attempts to remove hemicellulose for production of dissolving pulps with very low hemicellulose contents have shown that complete enzymatic hydrolysis of hemicellulose within the pulp is difficult to achieve. The xylan content in delignified mechanical aspen pulp was reduced from approximately 20 to 10%, whereas in bleached hardwood sulphite pulp the xylan content was decreased from 4 to only 3.5% even at very high enzyme dosages (50). The complete removal of residual hemicellulose seems thus unattainable, apparently due to modification of the substrate or to structural barriers. 

Various diastereomeric di-, tri-, and tetrapeptides that carry the sterically demanding trifluoromethyl group instead of the natural a-proton at different positions within these short peptide sequences have been designed, and their stability towards enzymatic hydrolysis has been investigated. The structures of the a-trifluoromethyl (aTfm)-substituted amino acids are shown in Scheme 1. From these studies we gained valuable information on how a-trifluoromethyl-substi-tuted peptides may interact with proteins. The aTfm amino acids used in this study combine the conformational restrictions [49-52] of C -dialkylation with the unique stereoelectronic properties of the fluorine atom and have shown interesting effects on peptide-enzyme interactions [53,54]. 

The stability of the ester surfactants against enzymatic hydrolysis by two different microbial Upases, Mucor miehei lipase (MML) and Candida antarc-tica lipase B (CALB) added separately to the surfactant solutions, was also investigated, see Fig. 5 [19]. It is obvious that hydrolysis of the unsubstituted surfactant is much faster with both CALB and MML than that of the substituted surfactants, i.e., increased steric hindrance near the ester bond leads to decreased hydrolysis rate. Since the specificity of the enzyme against its substrate is determined by the structure of the active site, it can be concluded, as expected, that the straight chain surfactant most easily fits into the active site of both enzymes. 

Chum, H. L. Black, S. Johnson, D. K. Sarkanen, K. V. Robert, D. Organosolv Pretreatment for the Enzymatic Hydrolysis of Poplars. II. Isolation and Quantitative Structural Studies of Lignins. Submitted. 

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