Enzymes decomposition

In the Talalay process, the froth is produced by chemical rather than mechanical means. Hydrogen peroxide and an enzyme decomposition catalyst are mixed iato the latex and the mixture placed ia the mold. Decomposition of the peroxide by the added enzyme results ia the Hberation of oxygen which causes the latex mix to foam and fill the mold. The foam is then rapidly chilled and CO2 is iatroduced to gel the latex. The gelled foam is then handled ia a manner similar to that used ia the Dunlop process. 

Gottlieb, S., and J. H. Geller Enzymic Decomposition of Lignin. Science... 

To date, biochemical engineers have concentrated heavily on modeling and analysis of the enzyme synthesis process and have almost completely ignored the enzyme decomposition processes which are important in many... 

Formaldehyde is directly emitted into the air from vehicles. It is released in trace amounts from pressed wood products such as particleboard and plywood paneling, from old sick bnildings, and from cotton and cotton-polyester fabrics with selected crosslink finishes. Formation of formaldehyde has been observed in some frozen gadoid fish due to enzymic decomposition of the additive trimethylamine oxide (Rehbein 1985). Its concentration can build up during frozen storage of fish (Leblanc and Leblanc 1988 Reece 1985). It occurs in the upper atmosphere, cloud, and fog it also forms in photochemical smog processes. 

Z-twist See twist, direction of yam. zymoplastic A substance that is not an enzyme but is beheved to participate in the formation of enzymes. See catalyst, enzyme decomposition degradation, zymurgy The branch of applied chemistry that has to do with fermentation processes. See decomposition waste. 

Rao, D.R., Greenberg, D.M. Studies on the enzymic decomposition of urocanic acid. II. Properties of products of urocanase reaction. Biochim. biophys. Acta (Amst.) 43, 404-418 (1960)... 

The above-considered calculational data point to high effectiveness of the bifunctional catalysis in hydrolytic reactions and the reactions related to these, due to involvement of molecular chains of water and ammonia, as well as to the preferability in these reactions of a concerted mechanism. This conclusion is fairly general and is corroborated by calculations on other types of nucleophilic reactions, such as hydrolysis of methyl fluoride, tautomerization of pyridine in aqueous solution etc. [110]. An advisable piece of work would apparently, be an analysis, in the light of the conclusions discussed, of mechanisms of the catalytic act in enzymic hydrolysis reactions of the ester and peptide bonds. In the most advanced up-to-date models for, e.g., the reactions with participation of a-chymotrypsin (see Ref. [Ill]), the steps of the base and the acid catalysis are separated. The latter is commonly thought [84, 111] to be operative at the stage of enzymic decomposition of the tetrahedral intermediate. However, taking into account the possibility of realization of the conformationally excited states of the active enzymic center, it would not be hard to think of some realistic schemes of concerted mechanisms, the more so that the fast growing body of calculational material continuously supplies fresh evidence in favor of such mechanisms. 

Additional confirmation of the scheme of the catabolism of valine shown in Fig. 5 has been provided by the studies of Coon and co-workers (87-90) on the enzymic decomposition of isobutyric acid and of Flavin, Ochoa, and co-workers (91-96) on the metabolism of propionic acid. 

Study of the enzymic reactions of histidine catabolism was aided tremendously by the observation that urocanic acid exhibits a strong absorption in the ultraviolet region with a maximum at 277 m/u and a molar extinction coefficient of 18,000 (S4S, XS6). This property renders it very convraiient to follow both the formation of urocanic acid from histidine and its disappearance spectrophotometrically. The observation that in the enzymic decomposition of urocanic acid a product with an absorption peak at 264 m i is formed also is of extreme importance in following the further sequence of the reactions of histidine catabolism 257, 258). 

The misconceptions expressed in these statements are obvious. It should be remembered that plotting enzymic decomposition of substrate versus time may give a straight line (zero order) or a die-away curve, simulating curves obtained for monomolecular reactions, or anything between these two extremes, or a two-phase curve, representing a combination of both. In no case can the decision whether a process is enzymic or not be based on the shape of time-activity curves. 

Enzyme-Catalyzed Reactions Enzymes are highly specific catalysts for biochemical reactions, with each enzyme showing a selectivity for a single reactant, or substrate. For example, acetylcholinesterase is an enzyme that catalyzes the decomposition of the neurotransmitter acetylcholine to choline and acetic acid. Many enzyme-substrate reactions follow a simple mechanism consisting of the initial formation of an enzyme-substrate complex, ES, which subsequently decomposes to form product, releasing the enzyme to react again. 

Hydrolysis. The first effect of either acid hydrolysis or alkaline hydrolysis (saponification) is the removal of the fatty acids. The saponification value of commercial lecithin is 196. Further decomposition into glycerol, phosphoric acid, and head groups (ie, choline, ethanolamine, etc) may foUow prolonged heating. Lecithin may also be hydrolyzed by enzymes. 

A significant difference between pseudoirreversible inhibitors and mechanism-based inactivators is the reversibiUty of the inactivation. A complete evaluation of the mechanism involved would require evidence not only for the covalent enzyme-inhibitor complex, but also for its decomposition products and its rate of reactivation. It is often difficult to identify the active site amino acid residue covalently linked to the inhibitor because of the instabiUty of the complex. 

Enzymes are proteins of high molecular weight and possess exceptionally high catalytic properties. These are important to plant and animal life processes. An enzyme, E, is a protein or protein-like substance with catalytic properties. A substrate, S, is the substance that is chemically transformed at an accelerated rate because of the action of the enzyme on it. Most enzymes are normally named in terms of the reactions they catalyze. In practice, a suffice -ase is added to the substrate on which die enzyme acts. Eor example, die enzyme dial catalyzes die decomposition of urea is urease, the enzyme dial acts on uric acid is uricase, and die enzyme present in die micro-organism dial converts glucose to gluconolactone is glucose oxidase. The diree major types of enzyme reaction are ... 

A catalyst is defined as a substance that influences the rate or the direction of a chemical reaction without being consumed. Homogeneous catalytic processes are where the catalyst is dissolved in a liquid reaction medium. The varieties of chemical species that may act as homogeneous catalysts include anions, cations, neutral species, enzymes, and association complexes. In acid-base catalysis, one step in the reaction mechanism consists of a proton transfer between the catalyst and the substrate. The protonated reactant species or intermediate further reacts with either another species in the solution or by a decomposition process. Table 1-1 shows typical reactions of an acid-base catalysis. An example of an acid-base catalysis in solution is hydrolysis of esters by acids. 

Decomposition of the complex to the product and free enzyme is assumed irreversible, and rate controlling ... 

Enzyme catalysis. An enzyme in the potato is catalyzing the decomposition of a hydrogen peroxide solution, as shown by the bubbles of oxygen. 

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