Derivatives of Enzymes

Immobilized Derivatives of Enzymes.—Techniques used to immobilize enzymes have been discussed. A mathematical model has been developed to assess how enzyme-catalysed reactions that involve the release or consumption of hydrogen ions behave when the enzyme is immobilized. The Proceedings of a symposium covering the analysis and regulation of immobilized enzymes have been published.  

A study of the mechanical properties ( mechanochemistry ) of immobilized enzymes (e.g. chymotrypsinogen trapped within a polyacrylamide gel) has provided a means whereby the chemical processes at a molecular level can be controlled by mechanical compression and decompression of the supporting gel (i.e. by controlling the pore size). Mechanical compression of a chymotrypsinogen-polyacrylamide gel resulted in a 20-fold increase in the diffusion-controlled tryptic activation of chymotrypsinogen, the reaction rate 

Analysis and Control of Immobilized Enzyme Systems, Proceedings of International Symposium organized by IRIA, 5-7 May 1975, ed. D. Thomas and J.-P. Kernevez, North-Holland Publishing Co., Amsterdam and New York, 1976. 

Matrix or macromolecule coupled Chelation by zirconium hydroxide 

Reaction with concanavalin A Reaction with acylazide-activated collagen 

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STEADY-STATE TREATMENT. During the steady state, the concentrations of various enzyme intermediates are essentially unchanged that is, the rate of formation of a given intermediate is equal to its rate of disappearance. This assumption was first introduced to the derivation of enzyme kinetic equations by Briggs and Haldane ... 

A method to assist the investigator in the derivation of enzyme-rate expressions. This method is schematic in nature, involving the drawing of all possible patterns of a geometric figure minus a loop. It is a very convenient... 

Activity-based strategies employ tests that are often applied directly to colonies to identify the desired activity. Nontoxic chemical dyes and insoluble or chromo-phore-bearing derivatives of enzyme substrates, for example, can be incorporated... 

VoUcenstein, M.V., Goldstein, B.N., 1966b. Method for derivation of enzyme kinetics equations. Biokhimiya 31, 541-547 (in Russian). 

Immobilized Derivatives of Enzymes.—The latest volume in the series Methods in Enzymology is devoted to such aspects of immobilized enzymes as immobilization techniques, the applications of immobilized enzymes to biochemistry and organic chemistry, and immobilized coenzymes, Reviews, etc., on diverse... 

Immobilized Derivatives of Enzymes.— Numerous reviews have appeared surveying the field of enzyme immobilization. - Diffusional influences on the parametric sensitivity of immobilized enzyme catalysts have been mathematically analysed. Particular account was taken of external mass transfer and intraparticle diffusion effects which can significantly influence the dependence of the observed reaction rate on operating parameters such as temperature and pH. 

In most cases of derivation of enzymes, a major part of the reactive substrate becomes attached to the protein. The appending of a large group to the active site probably accounts for the observation that most modified enzymes prepared in this way are inactive. 

Immobilized Derivatives of Enzymes.—The modification of enzymes to yield active water-insoluble or immobilized derivatives continues to receive attention. Reviews covering the principles of the technology of immobilized enzymes " and the preparation and uses of immobilized enzymeshave appeared. A compendium of data on the techniques used for the immobilization of enzymes, and books on the uses of immobilized enzymes in industrial reactors and in food and microbial processes have been published. 

Open-chain 1,5-polyenes (e.g. squalene) and some oxygenated derivatives are the biochemical precursors of cyclic terpenoids (e.g. steroids, carotenoids). The enzymic cyclization of squalene 2,3-oxide, which has one chiral carbon atom, to produce lanosterol introduces seven chiral centres in one totally stereoselective reaction. As a result, organic chemists have tried to ascertain, whether squalene or related olefinic systems could be induced to undergo similar stereoselective cyclizations in the absence of enzymes (W.S. Johnson, 1968, 1976). 

He/minthosporium (15). The mode of action is considered to be inhibition of the enzyme NADPH-cytochrome C reductase, which results in the generation of free radicals and/or peroxide derivatives of flavin which oxidize adjacent unsaturated fatty acids to dismpt membrane integrity (16) (see Enzyme inhibitors). 

Truncated Forms. Tmncated forms of hGH have been produced, either through the actions of enzymes or by genetic methods. 2-CAP, generated by the controlled actions of the trypsin, has the first eight residues at the N-terminus of hGH removed. Other tmncated versions of hGH have been produced by modification of the gene before expression in a suitable host. The first 13 residues have been removed to yield a derivative having distinctive biological properties (30). In this latter case the polypeptide chain is not cleaved. 

Identification, isolation, and removal of (polyhydroxy)benzenes from the environment have received increased attention throughout the 1980s and 1990s. The biochemical activity of the benzenepolyols is at least in part based on thek oxidation—reduction potential. Many biochemical studies of these compounds have been made, eg, of enzymic glycoside formation, enzymic hydroxylation and oxidation, biological interactions with biochemically important compounds such as the catecholamines, and humic acid formation. The range of biochemical function of these compounds and thek derivatives is not yet fully understood. 

In these procedures, the choice of derivatives and enzyme is important. Sometimes it is possible to get a D-amino acid which remains in the microbial culture supplemented with DL-amino acids (54). 

Vitamins are classified by their solubiUty characteristics iato fat-soluble and water-soluble groups. The fat-soluble vitamins A, E, and K result from the isoprenoid biosynthetic pathway. Vitamin A is derived by enzymic cleavage of the symmetrical C q beta-carotene, also known as pro-vitamin A. Vitamins E and K result from condensations of phytyldiphosphate (C2q) with aromatic components derived from shikimic acid. Vitamin D results from photochemical ring opening of 7-dehydrocholesterol, itself derived from squalene (C q). 

Various chemical species influence the rates of hydrolysis of penicillins, e.g. metal ions (Cu >Zn >Ni Co ) (80JCS(P2)1725), carbohydrates (78MI51101), certain amine-containing catechol derivatives (69JPS1102) and /3-cyclodextrin (71JA767). Some of these even show some of the characteristics of enzyme-catalyzed hydrolyses. 

The use of enzymes for the hydrolysis of acylals is effective, and in the case of racemic derivatives some enantioenrichment of the aldehyde is possible. ... 

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