Iron-Mediated Generation of the Neurotoxin 6-Hydroxydopamine Quinone by Reaction of Fatty Acid Hydroperoxides with Dopamine: A Possible Contributory Mechanism for Neuronal Degeneration in Parkinson's Disease
oic acid) in the presence of ferrousions in Tris buffer, pH 7.4, resulted in a relatively fast, oxygen-independent reaction exhibiting first-order kinetics with respect to both catecholamine and metal concentrations. Product analysis in the early stages revealed the presence of significant amounts of the quinone of the neurotoxin 6-hydroxydopamine, together with some aminochrome and ill-defined melanin-like
Mosses have substantial amounts of long chain C20 polyunsaturated fatty acids, such as arachidonic and eicosapentaenoic acid, in addition to the shorter chain C18 alpha-linolenic and linoleic acids, which are typical substrates of lipoxygenases in flowering plants. To identify the fatty acid substrates used by moss lipoxygenases, eight lipoxygenase genes from Physcomitrella patens were heterologously expressed in Escherichia coli, and then analyzed for lipoxygenase activity using linoleic, alpha-linolenic and arachidonic acids as substrates. Among the eight moss lipoxygenases, only seven were found to be enzymatically active in vitro, two of which selectively used arachidonic acid as the substrate, while the other five preferred alpha-linolenic acid. Based on enzyme assays using a Clark-type oxygen electrode, all of the active lipoxygenases had an optimum pH at 7.0, except for one with highest activity at pH 5.0. HPLC analyses indicated that the two arachidonic acid lipoxygenases form (12S)-hydroperoxy eicosatetraenoic acid as the main product, while the other five lipoxygenases produce mainly (13S)-hydroperoxy octadecatrienoic acid from alpha-linolenic acid. These results suggest that mosses may have both C20 and C18 based oxylipin pathways. Published by Elsevier Ltd.
Unified mechanism for polyunsaturated fatty acid autoxidation. Competition of peroxy radical hydrogen atom abstraction, .beta.-scission, and cyclization
作者:Ned A. Porter、Laura S. Lehman、Bruce A. Weber、Karl J. Smith
DOI:10.1021/ja00411a032
日期:1981.10
Controlled chemical synthesis of the enzymically produced eicosanoids 11-, 12-, and 15-HETE from arachidonic acid and conversion into the corresponding hydroperoxides (HPETE)
作者:E. J. Corey、Anthony Marfat、J. R. Falck、John O. Albright