Prolyl endopeptidase inhibitory activity of unsaturated fatty acids

Prolyl endopeptidase (PEP, EC 3.4.21.26) is widely distributed in various organs, particularly in the brains of amnestic patients. Evaluation of PEP levels in postmortem brains of Alzheimer's disease patients revealed significant increases in PEP activity, suggesting that a specific PEP inhibitor can be a good candidate for an antiamnestic drug. In this study, mono- and polyunsaturated fatty acids were investigated to determine their role as PEP inhibitors. Oleic, linoleic, and arachidonic acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) showed PEP inhibitory activities (IC50 values of 23.6 +/- 0.4, 43.8 +/- 1.8, 53.4 +/- 1.2, 99.4 +/- 1.2, and 46.2 +/- 1.0 microM, respectively), indicating that they were effective PEP inhibitors, with inhibition constant (Ki) values of 26.7 +/- 0.3, 51.0 +/- 0.7, 91.3 +/- 3.1, 247.5 +/- 2.6, and 89.0 +/- 2.3 microM, respectively. Oleic acid showed the highest PEP inhibitory activity. Dixon plots of PEP inhibition showed oleic, linoleic, and arachidonic acids, EPA, and DHA are noncompetitive inhibitors; despite higher IC50 values of these unsaturated fatty acids than strong natural inhibitors, they may have potential use in preventing memory loss.     

A Catabolic Activity of Sphingomonas wittichii RW1 in the Biotransformation of Carbazole

The well-known bacterium Sphingomonas wittichii RW1 catabolically degrades dibenzo-p-dioxin and dibenzofuran, as well as their chlorinated derivatives. The catabolic degradation of dioxin is initiated by a ring-hydroxylating dioxygenase. The biotransformation of carbazole by S. wittichii RW1 was determined in the present study. Dioxin dioxygenase from the dibenzofuran induced RW1 strain was thought to be unable to attack carbazole, which includes a heterocyclic aromatic dibenzopyrrole system. However, our results showed that carbazole was transformed to anthranilic acid and catechol. The color of the culture suspension changed upon addition of carbazole due to formation of a nitrogen-containing metabolite. Relevant metabolic intermediates were identified by gas chromatographic mass spectrometry and electrospray ionization time-of-flight mass spectrometry with comparison to the corresponding authentic compounds. The dioxygenase of the dibenzofuran induced RW1 attacked at the angular position adjacent to the nitrogen atom to give a dihydroxylated metabolic intermediate. Contrary to predictions made in previous reports, S. wittichii RW1 displayed positive catabolic activity toward carbazole.