Molecular modification, enzyme

The above definition of molecular chaperone is entirely fnnctional and contains no constraints on the mechanisms by which different chaperones may act. The term noncovalent is nsed to exclude those proteins that carry out posttranslational covalent modifications. Protein disulfide isomerise may seem to be an exception, bnt it is both a covalent modification enzyme and a molecular chaperone. It is helpful to think of a molecnlar chaperone as a fnnction rather than as a molecnle. Thns, no reason exists why a chaperone function shonld not be a property of the same molecnle that has other fnnctions. Other examples include peptidyl-prolyl isomerase, which possesses both enzymatic and chaperone activities in different regions of the molecnle, and the alpha-crystallins, which combine two essential fnnctions in the same molecnle in the lens of the eye-contribnting to the transparency and the refractive index reqnired for vision as well... 

Kraus, J. L. Isosterism and molecular modification in drug design tetrazole analogue of GABA effects on enzymes of the gamma-ami-nobutyrate system. Pharmacol. Res. Commun. 1983, 75, 183-189. 

Bioprecursors do not imply a temporary linkage between the active principle and a carrier group, but result from a molecular modification of the active principle itself. This modification generates a new compound, which is a substrate for metabolizing enzymes, leading to a metabolite that is the expected active principle. This approach exemplifies the active metabolite concept in a provisional way (e.g. sulindac, fenbufen, acyclovir, losartan). 

The role of amide bonds in molecular recognition, enzyme inhibition and protein stability has been probed by a variety of amide-bond surrogates with a variety of chemical modification to the peptide bond. Early work in this area on pseudopeptides, or amide-bond surrogates, has been reviewed by Spatola (95, 96). 

This development came about through a series of molecular modifications which began with the basic observation that certain sulfonamide drugs inhibit the enzyme carbonic anhydrase. The diuretic acetazolamide was one practical result of such investigations. 

A much more ambitious database that builds on the IUBMB classification is BRENDA, maintained by the Institute of Biochemistry at the University of Cologne. In addition to the data provided by the ENZYME database, the BRENDA curators have extracted a large body of information from the enzyme literature and incorporated it into the database. The database format strives to be readable by both humans and machines. The categories of data stored in BRENDA comprise the EC-number, systematic and recommended names, synonyms, CAS-registry numbers, the reaction catalyzed, a list of known substrates and products, the natural substrates, specific activities, KM values, pH and temperature optima, cofactor and ion requirements, inhibitors, sources, localization, purification schemes, molecular weight, subunit structure, posttranslational modifications, enzyme stability, database links, and last but not least an extensive bibliography. Currently, BRENDA holds entries for approximately 3500 different enzymes. 

One of the fields of chemical application of alkaloids is the development of biosensDrs. Alkaloids and their regulatory function of enzymes, metabolism, and CNS are suitable molecules for the sensory investigation and biosensor research and development area. Moreover, a molecular modification of alkaloids is a large area in the chemical application of alkaloids. Synthetic alkaloids and transformation of natural or semi-natural and S5mthetic molecules are also chemical applications. A good example is natural alkaloid piperidine, which presently is also S5mthetically produced by different methods of sjmthesis. ... 

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