myo-Inositol phosphate isomers generated by the action of a phytate-degrading enzyme from Klebsiella terrigena on phytate

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Abstract:

For the first time a dual pathway for dephosphorylation of myo-inositol hexakisphosphate by a histidine acid phytase was established. The phytate-degrading enzyme of Klebsiella terrigena degrades myo-inositol hexakisphosphate by stepwise dephosphorylation, preferably via D-Ins(1,2,4,5,6)P5, D-Ins(1,2,5,6)P4, D-Ins(1,2,6)P3, D-Ins(1,2)P2 and alternatively via D-Ins(1,2,4,5,6)P5, Ins(2,4,5,6)P4, D-Ins(2,4,5)P3, D-Ins(2,4)P2 to finally Ins(2)P. It was estimated that more than 98% of phytate hydrolysis occurs via D-Ins(1,2,4,5,6)P5. Therefore, the phytate-degrading enzyme from K. terrigena has to be considered a 3-phytase (EC 3.1.3.8). A second dual pathway of minor importance could be proposed that is in accordance with the results obtained by analysis of the dephosphorylation products formed by the action of the phytate-degrading enzyme of K. terrigena on myo-inositol hexakisphosphate. It proceeds preferably via D-Ins(1,2,3,5,6)P5, D-Ins(1,2,3,6)P4, Ins(1,2,3)P3, D-Ins(2,3)P2 and alternatively via D-Ins(1,2,3,5,6)P5, D-Ins(2,3,5,6)P4, D-Ins(2,3,5)P3, D-Ins(2,3)P2 to finally Ins(2)P. D-Ins(2,3,5,6)P4, D-Ins(2,3,5)P3, and D-Ins(2,4)P2 were reported for the first time as intermediates of enzymatic phytate dephosphorylation. A role of the phytate-degrading enzyme from K. terrigena in phytate breakdown could not be ruled out. Because of its cytoplasmatic localization and the suggestions for substrate recognition, D-Ins(1,3,4,5,6)P5 might be the natural substrate of this enzyme and, therefore, may play a role in microbial pathogenesis or cellular myo-inositol phosphate metabolism.Key words: myo-inositol phosphate isomers, phytate-degrading enzyme, phytate, phytase, Klebsiella terrigena.

Pour la première fois, une voie double pour la déphosphorylation du myo-inositol hexakisphosphate par une phytase à histidine acide fut révélée. L'enzyme dégradant le phytate de Klebsiella terrigena dégrade préférablement le myo-inositol hexakisphosphate par une déphosphorylation progressive via le D-Ins(1,2,4,5,6)P5, D-Ins(1,2,5,6)P4, D-Ins(1,2,6)P3, D-Ins(1,2)P2 et alternativement via le D-Ins(1,2,4,5,6)P5, Ins(2,4,5,6)P4, D-Ins(2,4,5)P3, D-Ins(2,4)P2 jusqu'au produit final Ins(2)P. Nous avons estimé que plus de 98 % de l'hydrolyse du phytate passe par le D-Ins(1,2,4,5,6)P5. Par conséquent, l'enzyme dégradant le phytate de K. terrigena doit être considérée comme une 3-phytase (EC 3.1.3.8). Une autre voie double d'importance mineure a pu être mise de l'avant conformément avec les résultats obtenus par l'analyse des produits de déphosphorylation formés par l'action de l'enzyme dégradant le phytate de K. terrigena sur le myo-inositol hexakisphosphate. Celle-ci passe par le D-Ins(1,2,3,5,6)P5, D-Ins(1,2,3,6)P4, Ins(1,2,3)P3, D-Ins(2,3)P2 et alternativement par le D-Ins(1,2,3,5,6)P5, D-Ins(2,3,5,6)P4, D-Ins(2,3,5)P3, D-Ins(2,3)P2 jusqu'au produit final Ins(2)P. D-Ins(2,3,5,6)P4, D-Ins(2,3,5)P3 et D-Ins(2,4)P2 ont été mentionnés pour la première fois comme intermédiaires de la déphosphorylation enzymatique du phytate. Nous n'avons pu écarter un rôle de l'enzyme dégradant le phytate de K. terrigena dans la décomposition du phytate, mais selon sa localisation cytoplasmique et les suggestions de reconnaissance des substrats, le D-Ins(1,2,4,5,6)P5 pourraient bien être le substrat naturel de cette enzyme et pourrait donc jouer un rôle dans la pathogenèse microbienne ou le métabolisme cellulaire du myo-inositol phosphate.Mots clés : isomères du myo-inositol phosphate, enzyme dégradant le phytate, phytate, phytase, Klebsiella terrigena.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: August 1, 2006

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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