Enzymic indicators

Nomenclature. The compound on which the enzyme acts is known as the substrate. The name of the enzyme is now usually obtained by adding the termination ase to the name of the substrate. Thus an enzyme which hydrolyses an ester is known as an esterase. Nevertheless the older names of many enzymes still persist owing to their early disco ieiy. In some cases the name of the enzyme indicates the reaction w hich it catalyses, e.g. oxidase. 

Many reactions classified as dehydrogenations occur within the cells of living sys terns at 25°C H2 is not one of the products however Instead the hydrogens are lost m separate steps of an enzyme catalyzed process The enzyme indicated m the reaction... 

Figure26-2. Biosynthesis of squalene, ubiquinone, dolichol, and other polyisoprene derivatives. (HMG, 3-hydroxy-3-methylglutaryl x, cytokinin.) A farnesyl residue is present in heme a of cytochrome oxidase. The carbon marked with asterisk becomes C or C,2 in squalene. Squalene synthetase is a microsomal enzyme all other enzymes indicated are soluble cytosolic proteins, and some are found in peroxisomes.

Drinking large amounts of diisopropyl methylphosphonate kills animals. The amount needed to cause death in humans is not known for sure. Animal studies have shown no evidence that drinking or eating diisopropyl methylphosphonate causes fertility problems or birth defects. Animal studies have shown that eating diisopropyl methylphosphonate can affect some liver enzymes (indicating a response by the liver). However, test animals showed no liver disease. While most animal studies have shown only minimal toxic effects below a certain level of... 

Enzymes require an optimum pH at which their catalytic activity is maximal. The pH-activity profiles of enzymes indicate the pH at which the catalytic sites are in their necessary state of ionization. The optimal pH of an enzyme may be different from that of its normal environment. The action of enzymes in cells may be regulated by variation in the pH of the surrounding medium. 

The long-lived phosphorescence of the tryptophan in alkaline phosphatase is unusual. Horie and Vanderkooi examined whether its phosphorescence could be detected in E. coli strains which are rich in alkaline phosphatase.(89) They observed phosphorescence at 20°C with a lifetime of 1.3 s, which is comparable to the lifetime of purified alkaline phosphatase (1.4 s). Long-lived luminescence was not observed from strains deficient in alkaline phosphatase. The temperature dependence of tryptophan phosphorescence in the living cells was slightly different from that for the purified enzyme, indicating an environmental effect. 

Another way of perturbing the commitments is solvent deuteration. Change of the carbon kinetic isotope effect in the case of E. coli enzyme indicates that the proton transfer precedes the decarboxylation step ... 

Hepatic Effects. Enlarged liver and elevated serum levels of hepatic enzymes indicative of liver injury (lactate dehydrogenase, 2 times above normal aspartate aminotransferase, 21 times above normal alanine aminotransferase, 100 times above normal) were observed in an individual following chronic daily exposure to vapors and spills of phenol (Merliss 1972). The symptoms lessened when the... 

The E in the acronym ELISA stands for enzyme, indicating that an enzyme is linked, or conjugated, to one of the reactants, most commonly to the antibody. 

The goal of the experiments we report was to create new structural model complexes for gluzincins or carboxypeptidases. With [Zn (bdtbpza)Cl] (12) for the first time a tetrahedral zinc complex with a monoanionic W,W,0-tridentate using a carboxylate 0-donor was synthesized (41). A comparison of the molecular structure of 12 with the coordination environment of the enzymes indicates its significance... 

Unfortunately, the size of the crystallographic problem presented by elastase coupled with the relatively short lifedme of the acyl-enzyme indicated that higher resolution X-ray data would be difficult to obtain without use of much lower temperatures or multidetector techniques to increase the rate of data acquisition. However, it was observed that the acyl-enzyme stability was a consequence of the known kinetic parameters for elastase action on ester substrates. Hydrolysis of esters by the enzyme involves both the formation and breakdown of the covalent intermediate, and even in alcohol-water mixtures at subzero temperatures the rate-limidng step is deacylation. It is this step which is most seriously affected by temperature, allowing the acyl-enzyme to accumulate relatively rapidly at — 55°C but to break down very slowly. Amide substrates display different kinetic behavior the slow step is acylation itself. It was predicted that use of a />-nitrophenyl amid substrate would give the structure of the pre-acyl-enzyme Michaelis complex or even the putadve tetrahedral intermediate (Alber et ai, 1976), but this experiment has not yet been carried out. Instead, over the following 7 years, attention shifted to the smaller enzyme bovine pancreatic ribonuclease A. 

MMO has been identified as a member of the binuclear octahedral iron family (Woodland et al., 1986 Fox et al., 1988). The enzyme can hydrox-ylate a wide variety of hydrocarbons, including some toxic waste compounds hence, the enzyme has elicited considerable interest beyond its contribution to binuclear iron chemistry and mechanisms of oxygen activation. Although we do not have a crystal structure and have only limited spectroscopic data, the properties of the enzyme indicate that it should be considered with the other oxygen-activating binuclear iron proteins. 

Fig. 3 Metabolic routes towards biopolyester synthesis. Dashed lines represent engineered biosynthesis routes. Triangles depict targets for inhibitors enabling biopolyester synthesis. Enzymes indicated on shaded boxes on solid lines are biopolyester biosynthesis enzymes. With kind permission from Springer Science+Business Media [7]...

Exploitable structural differences between T.brucei(full) and human (dashed) TIM. The inhibitor 2-phosphoglycolate as observed in the structure of the human enzyme indicates the location of the active site. Drug design targets are the T.brucei AlalOO-TyrlOl, which are considerably different from their human counterpart His-Val. (From Ref.25. Copyright 1994 by Cambridge University Press.)... 

It undergoes marked self-association and can be purified readily by chromatography on porous glass. The enzyme has a molecular weight of about 89 kDa, a pH optimum of 6.8-7.0, and a temperature optimum of 35°C. Its amino acid composition, its requirement for iron but not for molybdenum and FAD, and the catalytic properties of the enzyme, indicate that sulphydryl oxidase is a distinct enzyme from xanthine oxidase and thiol oxidase (EC 1.8.3.2). 

Careful consideration of the role of these enzymes indicates that no... 

Degradation of the glycosaminoglycan heparan sulfate by lysosomal enzymes, indicating sites of enzyme deficiencies in some representative mucopolysaccharidoses. 

In fact, kinetic studies of the GTP-dependent avian mitochondrial enzyme indicate two metal-binding sites, one on the polyphosphate group of the bound GTP and one on carboxylate side chains of the protein.252 255 The three-dimensional structure of the ATP-dependent E. coli enzyme reveals a nucleotide binding site similar to the ATP site of adenylate kinase (Fig. 12-30).256 A definite binding site for C02 is also present in the enzyme.257... 

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