Feedback inhibition of homoserine dehydrogenase and threonine deaminase in the genusBifidobacterium |
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| Authors: | Annarosa Selli Franca Crociani Diego Matteuzzi Giorgio Crisetig |
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| Affiliation: | (1) Institute of Biochemistry, Faculty of Veterinary Medicine, University of Bologna, I-40126 Bologna, Italy;(2) Institute of Agricultural Microbiology, University of Bologna, I-40126 Bologna, Italy;(3) Institute of Fermentation Chemistry and Industrial Microbiology, Faculty of Pharmacy, University of Bologna, I-40126 Bologna, Italy |
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| Abstract: | Feedback inhibition of crude and purified extracts of homoserine dehydrogenase and threonine deaminase activities in the genusBifidobacterium was studied. Homoserine dehydrogenase was partially or completely inhibited byl-threonine, and a marked inhibitory effect byl-isoleucine on threonine deaminase was observed. In the speciesBifidobacterium cuniculi high levels ofl-valine reversed the inhibitory effect ofl-isoleucine. The  -aminobutyric acid-resistant mutant Ru 326/106 of the speciesB. ruminale, overproducer ofl-isoleucine, had a derepressed homoserine dehydrogenase and a lesser feedback inhibition byl-threonine. Homoserine dehydrogenase appeared to be in bifids specifically NAD dependent. The regulatory mechanisms of aspartate family amino acid biosynthesis in bifidobacteria was discussed. |
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