Đang chuẩn bị liên kết để tải về tài liệu:
Enzymes in the Environment: Activity, Ecology and Applications - Chapter 18

Haloorganics, còn được gọi là halogen hóa các hợp chất, là một tập hợp các hợp chất có chứa một liên kết carbon-halogen (halogen bao gồm các ion clorua, florua, bromide, và iốt). Trong số các phản ứng enzyme, sự thoái hóa các hợp chất chứa halogen-đã nhận được sự chú ý đáng kể. Trong môi trường tự nhiên halogen hóa những hợp chất rất phong phú (1). Các nguồn tự nhiên của haloorganics bao gồm tảo bẹ, rong biển và tảo biển và được giải phóng trong quá trình phun trào miệng núi lửa và thủy nhiệt (2,3). Số. | 18 Microbial Dehalogenation Reactions in Microorganisms Lee A. Beaudette Michael B. Cassidy Marc Habash Hung Lee and Jack T. Trevors University of Guelph Guelph Ontario Canada William J. Staddon Eastern Kentucky University Richmond Kentucky I. INTRODUCTION Haloorganics also known as halogenated compounds are a set of compounds that contain a carbon-halogen bond halogens include chloride fluoride bromide and iodide ions . Among enzymatic reactions degradation of halogen-containing compounds has received considerable attention. In the environment naturally occurring halogenated compounds are abundant 1 . Natural sources of haloorganics include sea kelp seaweed and algae and are released during volcanic and hydrothermal vent eruptions 2 3 . Quantities of methyl chloride estimated at 5-50 Mt yr 1 may be released from the burning of vegetation 4 . Over 1500 naturally occurring halogenated organic compounds have been isolated to date. In the last 50 years synthetic i.e. xenobiotic haloorganics have been developed as pesticides soil fumigants refrigerants solvents warfare and disabling gases and chemical reagents Fig. 1 . However unlike naturally occurring halogenated compounds many xenobiotics are toxic are resistant to natural mechanisms of degradation and subsequently accumulate in the environment. By their design and nature synthetic multihalogenated compounds created for specific uses are recalcitrant to microbial metabolism. It has been suggested that these compounds are not properly recognized by uptake proteins regulatory proteins or essential catabolic enzymes 5 and that a lack of a suitable set of catabolic enzymes is responsible for this recalcitrance rather than thermodynamics 6 . Recent inputs as a result of direct application accidental spills and inadequate disposal have resulted in levels of halogenated compounds that exceed the capacity of microorganisms to degrade them. Halogenated compounds are found in terrestrial and aquatic environments and some are