期刊名称：Journal of Nutritional Science and Vitaminology
印刷版ISSN：0301-4800
电子版ISSN：1881-7742
出版年度：2011
卷号：57
期号：5
页码：377-382
DOI：10.3177/jnsv.57.377
出版社：Center for Academic Publications Japan
摘要：α-Lipoic acid (LA) is a naturally occurring disulfide-containing compound used as an antioxidant supplement which also has been used as a medicine for diabetic neuropathy in Europe. Physiologically LA acts as a coenzyme of mitochondrial multienzyme complex in its protein bound form but it is not yet clear how the externally administrated LA is incorporated into other proteins in the same protein-bound form or why the bound form is active as an antioxidant. The binding and cleavage of LA to or from the protein is mediated by lipoamidase and thus determines LA distribution in tissues. We have developed a simple sensitive assay for lipoamidase using a fluorescent substrate, dansyl-α-lipoyllysine (DLL). Lipoamidase in tissues cleaves the amide bond between LA and the ε-amino-lysine moiety to release dansylated lysine (DL). A HPLC comparison of the fluorescence intensity between DLL and DL was used to quantify the enzyme activity. The hydrolytic reaction did not occur when the tissue was heat-treated before incubation with DLL and was inhibited by free LA, especially by the R-enantiomer of LA (physiologically active form). N ε-Acetyl- L -lysine did not compete with DLL in the cleavage reaction. The method was applied for the determination of lipoamidase activity levels in various rat tissues. It was revealed the spleen had the highest activity followed by the kidney, heart, lung and liver. The activity in the brain was below the detection limit of the assay.
