Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.8 (phytase)
 1,997 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mobilization of Ca2+ from microsomal/vacuolar fractions was detected when InsP6-phytase was added after a definite time of hydrolysis which coincides with the time (20-30 min) of optimal production of Ins(2,4,5)P3 bound to phytase. The in vitro constituted Ins(1,4,5)P3 or Ins(2,4,5)P3-phytase complex is also effective in releasing Ca2+. InsP3-phytase complex releases 45% more microsomal Ca2+ than that released by free InsP3 under identical conditions. Other inositol-phytase complexes are ineffective. Furthermore InsP3-phytase complex is recognised by putative receptor associated with microsomal fraction suggesting that the myoinositol tris-phosphate-phytase complex can act as an elicitor in Ca2+ mobilization in plant systems where phytate and phytase occur.
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PMID:Myoinositol tris-phosphate-phytase complex as an elicitor in calcium mobilization in plants. 838 39

One of the myoinositol trisphosphates produced by the phytase-myoinositol hexakisphosphate (InsP6) reaction is Ins(2,4,5)P3. That Ins(2,4,5)P3 can elicit Ca2+ mobilization from intracellular stores in plants [Samanta, S., Dalal, B., Biswas, S., & Biswas, B.B.(1993) Biochem. Biophys. Res. Commun. 191,427] prompted us to elucidate the mechanism. The InsP3 [Ins(1,4,5)P3/Ins(2,4,5)P3]-phytase complex has been found to interact with the receptor for InsP3 in vitro forming a ternary complex, and a nanomolar concentration of InsP3 is required. For enzymatic cleavage of InsP3 by phytase, micromolar concentrations are needed, and the affinities of the phytase for different myoinositol phosphates have been found to depend upon the number of phosphate groups present in the substrate. Fraction accessibility of tryptophan residues to a neutral fluorescence quencher, acrylamide in free and myoinositol phosphates bound phytase, as determined by Stern-Volmer plot, records a progressive decrease starting from InsP6 to InsP with the notable exceptions of both Ins (1,4,5)P3 and Ins(2,4,5)P3. This deviation from the trend of change in the accessibility of tryptophan residues in myoinositol phosphate bound phytase is recorded from the fact that there is a high affinity (dissociation constant of the nanomolar order) and noncatalytic binding site in phytase for the two isomers of InsP3. In the nanomolar range of concentrations, both isomers of InsP3 bind to a second site of phytase having about 40-fold higher affinity than the normal substrate binding site. InsP3, when bound to noncatalytic site in phytase is not hydrolyzed but induces a significant change in the conformation of phytase as assayed from the relative accessibility of tryptophan residues. This conformational change in phytase is recognized by the receptor for InsP3, because in absence of InsP3 no interaction between the receptor and phytase is detected. However, InsP3-phytase complex is a better elicitor of Ca2+ efflux from microsomal/vacuolar fractions than free InsP3. This is further confirmed by the fact that when Ins(1,3,4)P3-phytase complex can elicit Ca2+ efflux from intracellular stores, Ins(1,3,4)P3 per se is minimally effective.
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PMID:Interaction of myoinositoltrisphosphate-phytase complex with the receptor for intercellular Ca2+ mobilization in plants. 866 92