Biomaterial Database

Metabolism of inositol 1,4,5-trisphosphate in squid photoreceptors. 1990

S F Wood, and E Z Szuts, and A Fein

Marine Biological Laboratory, Woods Hole, MA 02543.

Inositol 1,4,5-trisphosphate (InsP3) is rapidly formed in squid photoreceptors in response to light, where it is converted sequentially into inositol bisphosphate (InsP2) and inositol monophosphate (InsP1). All of the InsP3 appears to be degraded to inositol 1,4-bisphosphate via an InsP3-phosphatase, which is characterized in this study. The enzyme is water-soluble and present in the light-transducing distal segments of squid photoreceptors. It has a Km of 50 microM for InsP3, requires Mg++ for its activity, is maximally active at neutral pH, specifically hydrolyses the 5-phosphate and is inhibited by 2,3-diphosphoglycerate. In these respects, InsP3-phosphatase of squid is very similar to the enzymes of other cells. Since no InsP4 or more highly phosphorylated inositols are found in squid photoreceptors, the InsP3-phosphatase may be important in the regulation of InsP3 concentration within these cells.

UI	MeSH Term	Description	Entries
D010744	Phosphoric Monoester Hydrolases	A group of hydrolases which catalyze the hydrolysis of monophosphoric esters with the production of one mole of orthophosphate.	Phosphatase,Phosphatases,Phosphohydrolase,Phosphohydrolases,Phosphomonoesterase,Phosphomonoesterases,Phosphoric Monoester Hydrolase,Hydrolase, Phosphoric Monoester,Hydrolases, Phosphoric Monoester,Monoester Hydrolase, Phosphoric
D010786	Photoreceptor Cells	Specialized cells that detect and transduce light. They are classified into two types based on their light reception structure, the ciliary photoreceptors and the rhabdomeric photoreceptors with MICROVILLI. Ciliary photoreceptor cells use OPSINS that activate a PHOSPHODIESTERASE phosphodiesterase cascade. Rhabdomeric photoreceptor cells use opsins that activate a PHOSPHOLIPASE C cascade.	Ciliary Photoreceptor Cells,Ciliary Photoreceptors,Rhabdomeric Photoreceptor Cells,Rhabdomeric Photoreceptors,Cell, Ciliary Photoreceptor,Cell, Photoreceptor,Cell, Rhabdomeric Photoreceptor,Cells, Ciliary Photoreceptor,Cells, Photoreceptor,Cells, Rhabdomeric Photoreceptor,Ciliary Photoreceptor,Ciliary Photoreceptor Cell,Photoreceptor Cell,Photoreceptor Cell, Ciliary,Photoreceptor Cell, Rhabdomeric,Photoreceptor Cells, Ciliary,Photoreceptor Cells, Rhabdomeric,Photoreceptor, Ciliary,Photoreceptor, Rhabdomeric,Photoreceptors, Ciliary,Photoreceptors, Rhabdomeric,Rhabdomeric Photoreceptor,Rhabdomeric Photoreceptor Cell
D004163	Diphosphoglyceric Acids	Glyceric acids where two of the hydroxyl groups have been replaced by phosphates.	Bisphosphoglycerates,Acids, Diphosphoglyceric
D000072181	Inositol Polyphosphate 5-Phosphatases	Phosphoinositide phosphatases that catalyze the removal of the 5' phosphate from INOSITOL 1,4,5-TRISPHOSPHATE or myo-inositol 1,3,4,5-tetrakisphosphate, resulting in inositol 1,4-bisphosphate and phosphate. They have important functions in the metabolism of INOSITOL PHOSPHATES and inositol 1,4,5-trisphosphate signaling pathways such as CALCIUM SIGNALING.	1,4,5-Triphosphate-1,2,4,5-Tetrakisphosphate 5-Phosphatase,Inositol 5-Phosphatase,Inositol Polyphosphate 5-Phosphatase,Inositol Triphosphate 5-Phosphatase,Inositol-1,4,5-Trisphosphate 5'-Phosphatase,Inositol-1,4,5-Trisphosphate 5-Phosphatase,Inositol-Polyphosphate 5-Phosphatase,Ins(1,4,5)P3 5'-Phosphatase,Inositol 5 Phosphatase,Inositol Polyphosphate 5 Phosphatase,Inositol Polyphosphate 5 Phosphatases,Inositol Triphosphate 5 Phosphatase
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013379	Substrate Specificity	A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.	Specificities, Substrate,Specificity, Substrate,Substrate Specificities
D015544	Inositol 1,4,5-Trisphosphate	Intracellular messenger formed by the action of phospholipase C on phosphatidylinositol 4,5-bisphosphate, which is one of the phospholipids that make up the cell membrane. Inositol 1,4,5-trisphosphate is released into the cytoplasm where it releases calcium ions from internal stores within the cell's endoplasmic reticulum. These calcium ions stimulate the activity of B kinase or calmodulin.	1,4,5-InsP3,Inositol 1,4,5-Triphosphate,Myo-Inositol 1,4,5-Trisphosphate,1,4,5-IP3,Myoinositol 1,4,5-Triphosphate
D049832	Decapodiformes	A superorder of CEPHALOPODS comprised of squid, cuttlefish, and their relatives. Their distinguishing feature is the modification of their fourth pair of arms into tentacles, resulting in 10 limbs.	Cuttlefish,Illex,Sepiidae,Squid,Todarodes,Cuttlefishs,Decapodiforme,Illices,Squids,Todarode
D019794	2,3-Diphosphoglycerate	A highly anionic organic phosphate which is present in human red blood cells at about the same molar ratio as hemoglobin. It binds to deoxyhemoglobin but not the oxygenated form, therefore diminishing the oxygen affinity of hemoglobin. This is essential in enabling hemoglobin to unload oxygen in tissue capillaries. It is also an intermediate in the conversion of 3-phosphoglycerate to 2-phosphoglycerate by phosphoglycerate mutase (EC 5.4.2.1). (From Stryer Biochemistry, 4th ed, p160; Enzyme Nomenclature, 1992, p508)	2,3-Bisphosphoglycerate,2,3-DPG,2,3-Diphosphoglyceric Acid,2,3-Diphosphoglycerate, (D)-Isomer,Glycerate 2,3-Bisphosphate,2,3 Bisphosphoglycerate,2,3 Diphosphoglycerate,2,3 Diphosphoglyceric Acid,2,3-Bisphosphate, Glycerate