Reductive biotransformations

Shen H, GW Sewell (2005) Reductive biotransformation of tetrachloroethene to ethene during anaerobic degradation of toluene experimental evidence and kinetics. Environ Sci Technol 39 9286-9294. 

Okutman-Tas D, Pavlostathis SG (2007) The influence of iron reduction on the reductive biotransformation of pentachloronitrobenzene. Eur J Soil Biol 43 264—275... 

Fariss MW, Blanke RV, Boylan J J, et al. 1978. Reductive biotransformation of chlordecone in man and rat. Toxicol Appl Pharmacol 45 337. 

Testai E, Gramenzi F, Di Marzio S, et al. 1987. Oxidative and reductive biotransformation of chloroform in mouse liver microsomes. Mechanisms and Models in Toxicology Arch Toxicol Suppl 11 42-44. 

Reductive biotransformation of a contaminant can occur when the contaminant serves as the terminal electron acceptor. Many contaminants that are recalcitrant to bio-oxidation will undergo reductive biotransformations. These biotransformations can lead to detoxification, mineralization, or changes in the mobility of the targeted contaminant. Hexavalent chromium and tetra-chloroethene (PCE) have been investigated as candidates for reductive biotransformation. This technology may be most applicable for in situ remediation for the following scenarios PCE contamination, low-yield aquifers, areas contaminated by both alkylbenzenes and chlorinated ethenes, and deep aquifer contamination. 

Free metabolites produced by addition, cleavage, oxidation and reduction biotransformations of the parent compound... 

Godoy, H.M., Diaz Gomez, M.l. Castro, J.A. (1984) Metabolism and activation of 1,1-di-methylhydrazine and methylhydrazine, two products of Wnitrosodimethylamine reductive biotransformation. In O Neill, I.K., von Borstel, R.C., Miller, C.T., Long, J. Bartsch, H., eds, El-Nitroso Compounds Occurrence, Biological Effects and Relevance to Human Cancer (lARC Scientific Publications No. 57), Lyon, lARC, pp. 479-484... 

OP Ward, CS Young. Reductive biotransformations of organic compounds by cells or enzymes of yeast. Enzyme Microb Technol 12 482 493, 1990. 

Reductive biotransformation processes are less common than those involving oxidation, but a number of functional groups are susceptible to reduction. 

The types of nitrogen-containing compounds that are most frequently involved in reductive biotransformation are those containing nitro, azo, and N-oxide functional groups. Similar enzymes are involved that are generally located in the endoplasmic reticulum or cytosol of the liver or in the intestinal microflora. Complete reduction of a nitro compound to the primary amine involves a six-electron transfer and proceeds through nitroso and hydroxylamine intermediates [Eq. (16)]. 

Reductive biotransformations of several compounds such as polyhalogenated, keto, nitro and azo derivatives, are... 

FIGURE 33.15 Reductive biotransformation of nitro arene compounds. 

Godoy HM, Gomez MI, Castro JA. 1983. Metabolism and activation of 1,1-dimethylhydrazine and methylhydrazine, two products of nitrosodimethylamine reductive biotransformation, in rats. J Natl Cancer Inst 5 1047-1051. 

Reductive biotransformations of several compounds such as polyhalogenated, keto, nitro and azo derivatives, are catalysed by a variety of enzymes which differ according to the substrates and the species. The liver cytochrome P-450-dependent drug metabolizing system is capable of reducing Af-oxide, nitro and azo bonds, whereas the cytosolic nitrobenzene reductase activity is mainly due to cytochrome P-450 reductase, which transforms nitrobenzene into its hydroxylamino derivative. NADPH cytochrome c reductase is also able to catalyse the reduction of nitro compounds. These metabolic conversions may also be brought about by gastrointestinal anaerobic bacteria. 

The reductive biotransformation of drugs has been one of the least studied reactions, and many of the enzymes that are involved have not been well characterized. Some of the enzymes that catalyze reductive reactions of drugs are the cytochrome P450s, molybdenum reductases, alcohol dehydrogenases, carbonyl reductases, NADPH cytochrome P450 reductase, NAD(P)H— quinone oxidoreductases, and enzymes of the intestinal microflora (Matsunaga et al., 2006 Rosemond and Walsh, 2004). 

Wood, O. P., Young, C. S. (1990). Reductive Biotransformations of Organic Compounds by Cells or Enzymes of Yeast. Enzyme Microb. Technol, 12,482. 

A number of reductive biotransformations of acyl silanes into a-hydroxy silanes have appeared recently. Acetyl dimethylphenylsilane is converted into (/f)-(l-hydroxyethyl) dimethylphenylsUane by plant cell suspension cultures of Symphytum officinale L. and Ruta graveolens L. in low yields but in 81% ee and 6% ee, respectively . SUanol and disUoxane were observed as by-products. Microbial reduction of racemic acetyl t-butyldimethylsilane has been achieved using Trigonopsis variabilis (DSM 70714) and Corynebacterium dioxydans (ATCC 21766) on a 10- gramme scale with > 96% ee in each case and in up to 78% yield . Recently, Saccharomyces cerevisiae (DHWS 3), a commercially available form of bakers yeast, has been shown to reduce acetyl dimethylphenylsilane, again to (/ )-(1-hydroxyethyl) dimethylphenylsilane, in 40% yield and >99.5% ee . 

Durchschein, K., Fabian, W.M.F., Macheroux, P., Zangger, K., Trimmel, G., and Faber, K. (2011) Reductive biotransformation of nitroalkenes via nitroso-intermediates to oxazetes catalyzed by xenobiotic reductase A (XenA). 0 g, Biomol. Chem., 9, 3364-3369. 

---