Mt. Rincon et al., ANAEROBIC DEGRADATION OF MIMOSINE-DERIVED HYDROXYPYRIDINES BY CELL-FREE-EXTRACTS OF THE RUMEN BACTERIUM SYNERGISTES JONESII, FEMS microbiology, ecology, 27(2), 1998, pp. 127-132
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.