{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,3]],"date-time":"2026-03-03T05:08:36Z","timestamp":1772514516249,"version":"3.50.1"},"reference-count":34,"publisher":"Wiley","issue":"1","license":[{"start":{"date-parts":[[2005,3,3]],"date-time":"2005-03-03T00:00:00Z","timestamp":1109808000000},"content-version":"vor","delay-in-days":4628,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["European Journal of Biochemistry"],"published-print":{"date-parts":[[1992,7]]},"abstract":"<jats:p>Basal and stimulated levels of inositol phosphates were determined in the protozoan <jats:italic>Paramecium<\/jats:italic> labelled with <jats:italic>myo<\/jats:italic>\u2010[<jats:sup>3<\/jats:sup>H]inositol. Under resting conditions, intracellular Ins<jats:italic>P<\/jats:italic><jats:sub>6<\/jats:sub> (phytic acid), Ins<jats:italic>P<\/jats:italic><jats:sub>5<\/jats:sub> and Ins<jats:italic>P<\/jats:italic><jats:sub>4<\/jats:sub> concentrations were 140, 10 and 2 \u03bcM, respectively. Ins<jats:italic>P<\/jats:italic><jats:sub>5<\/jats:sub> was comprised of 56% Ins(1,2,3,4,5)<jats:italic>P<\/jats:italic><jats:sub>5<\/jats:sub> and\/or Ins(1,2,3,5,6)<jats:italic>P<\/jats:italic><jats:sub>5<\/jats:sub>, 40% Ins(1,2,4,5,6)<jats:italic>P<\/jats:italic><jats:sub>5<\/jats:sub> and\/or Ins(2,3,4,5,6)<jats:italic>P<\/jats:italic><jats:sub>5<\/jats:sub> and small amounts of Ins(1,3,4,5,6)<jats:italic>P<\/jats:italic><jats:sub>5<\/jats:sub> and Ins(1,2,3,4,6)<jats:italic>P<\/jats:italic><jats:sub>5<\/jats:sub>. Ins<jats:italic>P<\/jats:italic><jats:sub>4<\/jats:sub> was mainly Ins(1, 4, 5, 6)<jats:italic>P<\/jats:italic><jats:sub>4<\/jats:sub> and\/or Ins(3, 4, 5, 6)<jats:italic>P<\/jats:italic><jats:sub>4<\/jats:sub>. Other inositol phosphates were not detected at a detection limit of 50\u201385 nM. Using various depolarizing and hyperpolarizing stimuli, no significant changes in level of inositol phosphates were observed <jats:italic>in vivo<\/jats:italic>, indicating that in the ciliate a contribution of inositol phosphates to signal\u2010transduction mechanisms is unlikely. In homogenates prepared from <jats:italic>myo<\/jats:italic>\u2010[<jats:sup>3<\/jats:sup>H]inositol\u2010labelled cells, a marked relative increase in Ins<jats:italic>P<\/jats:italic><jats:sub>3<\/jats:sub> and Ins<jats:italic>P<\/jats:italic><jats:sub>4<\/jats:sub> over the concentrations <jats:italic>in vivo<\/jats:italic> was observed. These inositol phosphates were identified as degradation products of endogenous Ins<jats:italic>P<\/jats:italic><jats:sub>6<\/jats:sub>. A novel separation methodology for inositol phosphates was established to allow unequivocal assignment of phosphate locations of all dephosphorylated Ins<jats:italic>P<\/jats:italic><jats:sub>6<\/jats:sub>\u2010derived products. The dephosphorylation was catalyzed by a phytase\u2010like enzyme with a molecular mass of 240 kDa, most likely of a hexameric structure. The enzyme had a pH optimum of 7.0 and did not require divalent cations for activity. Substrate concentrations above 300 \u03bcM were inhibitory. Dephosphorylation of Ins<jats:italic>P<\/jats:italic><jats:sub>6<\/jats:sub> by the <jats:italic>Paramecium<\/jats:italic> enzyme differs from that of phytases from plants in that it proceeds via a sequential release of phosphate groups from positions 6, 5, 4 and 3 of the <jats:italic>myo<\/jats:italic>\u2010inositol ring or\/and positions 4, 5, 6 and 1.<\/jats:p>","DOI":"10.1111\/j.1432-1033.1992.tb17058.x","type":"journal-article","created":{"date-parts":[[2005,3,4]],"date-time":"2005-03-04T07:28:49Z","timestamp":1109921329000},"page":"359-367","source":"Crossref","is-referenced-by-count":28,"title":["Metabolism of inositol phosphates in the protozoan <i>Paramecium<\/i>"],"prefix":"10.1111","volume":"207","author":[{"given":"Wolf\u2010Dietrich","family":"FREUND","sequence":"first","affiliation":[]},{"given":"Georg W.","family":"MAYR","sequence":"additional","affiliation":[]},{"given":"Cornelia","family":"TIETZ","sequence":"additional","affiliation":[]},{"given":"Joachim E.","family":"SCHULTZ","sequence":"additional","affiliation":[]}],"member":"311","published-online":{"date-parts":[[2005,3,3]]},"reference":[{"key":"e_1_2_3_2_2","doi-asserted-by":"publisher","DOI":"10.1038\/341197a0"},{"key":"e_1_2_3_3_2","doi-asserted-by":"publisher","DOI":"10.1111\/j.1432-1033.1990.tb19297.x"},{"key":"e_1_2_3_4_2","doi-asserted-by":"publisher","DOI":"10.1038\/330656a0"},{"key":"e_1_2_3_5_2","doi-asserted-by":"publisher","DOI":"10.1016\/0006-291X(87)90489-X"},{"key":"e_1_2_3_6_2","doi-asserted-by":"crossref","first-page":"18489","DOI":"10.1016\/S0021-9258(18)51493-9","article-title":"Mass changes in inositol tetrakis\u2010 and pentakisphosphate isomers induced by chemotactic peptide stimulation in HL\u201060 cells","volume":"264","author":"Pittet D.","year":"1989","journal-title":"J. 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