Enzymatic methods reduction

An enzymatic method to remove dioxins from fishmeal has been investigated using Coprinus cinereus peroxidase, cloned and expressed in Aspergillus sp. and did not result in a major degradation of dioxins with only 10-15% reduction achieved [120]. 

Suzuki and Banfield (1999) classify methods of microbial uranium accumulation as either metabolism dependent or metabolism independent. The former consists of precipitation or complexa-tion with metabohcally produced ligands, processes induced by active cellular pumping of metals, or enzyme-mediated changes in redox state. Examples include precipitation of uranyl phosphates due the activity of enzymes such as phosphatases, formation of chelating agents in response to metal stress, and precipitation of uraninite through enzymatic uranium reduction. 

Clearly, the determination of such compounds is crucial for diagnosis and monitoring of renal disease and metabolic disorders. The concentration of oxypurines in blood serum is among the most important parameters in biochemistry and clinical chemistry. Determination of uric acid is performed by enzymatic methods or colori-metrically by reduction of phosphotungstate. 

Baker s yeast offers the synthetic chemist an enzymatic method for the asymmetric reduction of p-keto esters, a-hydroxyaldehydes and ketones, and p-diketones. Reviews (a) Rene Csuk, R. Glaenzer, B. 1. Chem. Rev. 1991, 91, 49-97. (b) Servi, S. Synthesis, 1990, 1-25. 

Since CIgSiH is known to be activated by DMF and other Lewis bases to effect hydrosilylation of imines (Scheme 4.2) [8], it is hardly surprising that chiral formamides, derived from natural amino adds, emerged as prime candidates for the development of an asymmetric variant of this reaction [8]. It was assumed that, if successful, this approach could become an attractive altemative to the existing enzymatic methods for amine production [9] and to complement another organo catalytic protocol, based on the biomimetic reduction with Hantzsch ester, which is being developed in parallel [5]. 

Enzymatic methods generally offer greater specificity over conventional non-enzymatic colorimetric methods for the measurement of uric acid. Even so, methods that depend upon the use of oxidizing agents—such as phosphotungstic acid to oxidize uric acid to allantoin and carbon dioxide, and the resulting reduction of... 

Enzymatic methods rely on similar principles redox reactions involving the acids associated with either the oxidation of NADH or the reduction of NAD. The reaction is followed by the appearance or disappearance of NADH, which is measured spectrophotometrically at 340 nm. The primary reaction with the acid is often coupled to a second reaction in order to remove the product and thus drive the reaction equilibria to completion. Some of the possible reactions are summarized in the following schemes ... 

After treatment of (E)-27 with such usual reductants as NaBH4 or LiAlH4, the resultant (E)-26 would be resolved by the well-known Sharpless epoxidation protocoF or via enzymatic methods before or after epoxidation. 

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