ANAEROBIC DEGRADATION OF MIMOSINE-DERIVED HYDROXYPYRIDINES BY CELL-FREE-EXTRACTS OF THE RUMEN BACTERIUM SYNERGISTES JONESII

Synergistes jonesii is a rumen bacterium that degrades toxic pyridined iols from Leucaena leucocephala. This work presents progress on the ch aracterization of the degradation of dihydroxypyridines from L. leucoc ephala by S. jonesii, and particularly by its cell free extracts. The substrate 3-hydroxy-4-[1H]-pyridone (3,4-DHP) induced degradation of b oth 3,4- and 2,3-dihydroxypyridine (2,3-DHP) isomers, while 2,3-DHP in duced only degradation of 2,3-DHP. The 2,3-DHP was an intermediate of the degradation of 3,4-DHP by cultures. The compound 2,6-dihydroxypyri dine inhibited degradation of 2,3 DHP by extracts of cells previously induced with this substrate. Cell-free extracts from S, jonesii had a high hydrogenase activity and degraded 2,3-DHP anaerobically either in the presence of methyl viologen under H-2 or in the presence of alpha -ketoacids under H-2 or N-2. Specific activity of 2,3-DHP degradation was increased when FAD(+) or CoA were present. The pyridine ring of th e 2,3-DHP is enzymatically reduced by S. jonesii in reactions that dem and reducing power provided by hydrogenase activity or by the metaboli sm of pyruvate. An unidentified non-polar amino compound appeared in t hin layer chromatography as 2,3-DHP was degraded. We anticipate that g as chromatography mass spectrometry will permit the purification and i dentification of products from the cell-free reaction mix, which repre sents a simpler system than cell cultures, so that a pathway for pyrid inediol metabolism by S. jonesii can be proposed. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B .V. All rights reserved.