Chemical combination with enzyme

This glycan was extracted by a trichloroacetic acid method and purified to homogeneity by alcohol precipitation and bio-gel filtration methods. The complete molecular structure of the glycan has been deduced from data of methylation analysis in combination with enzymic and chemical degradation reactions (25,... 

Resolution of cheap racemic mixtures with enzymes is a common route to enantiomerically pure chemicals on an industrial scale. However, the yield with a classical resolution is limited to 50%. An in situ racemization of the undesired enantiomer, combined with the enzymatic kinetic resolution, gives rise to a dynamic kinetic resolution (DKR) that should in principle lead to a 100% yield in the desired isomer. In spite of several Ru and Pd homogeneous systems successfully combined with enzymes and successfully applied on industrial scale in DKR [71, 72], few metal-based heterogeneous catalysts active for alcohol racemization have been reported [19, 73, 74]. 

Although the precise mechanism by which each of the many environmental pollutants exerts toxicity remains to be elucidated, four principal mechanisms are described here. In general, a pollutant may cause an adverse effect on a living organism through (1) disruption or destruction of cellular structure (2) direct chemical combination with a cell constituent (3) its influence on enzymes and (4) initiation of a secondary action. These are examined below. 

Catalase has been studied intensively by chemical and physical methods. The protein component is not unusual in amino acid composition. The iron appears to be present only in the ferric form, and cannot be reduced chemically by any procedure that does not denature the enzyme. There is evidence, however, that during an enzymatic reaction with hydrazoic acid and hydrogen peroxide the iron is reduced to the ferrous state. The iron forms compounds with a large number of molecules. Some of these, such as HCN, HNs, and H2S, are inhibitors of the enzyme. The absorption spectrum of catalase shows bands at 403 m/i (Soret), 500 m/i, 540 m/B, and 629 m/t . These shift to give characteristic spectra when HCN, HN3, or HF combines with enzyme. Magnetic... 

Trichloroethylene may occur in drinking water along with other chlorinated hydrocarbons, so effects of these chemicals in combination are of interest to public health. Hepatotoxicity, as measured by plasma enzyme activity, was increased synergistically in rats by oral administration of carbon tetrachloride combined with trichloroethylene (Borzelleca et al. 1990). In addition, synergistic effects were implicated in a 3-day study in... 

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