Biomaterial Database

Smooth muscle aldolase C-bound inositol 1,4,5-trisphosphate studied in vitro under physiological conditions. 1998

C B Baron, and P Greeley, and R F Coburn

Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, USA. cbaron@mail.med.upenn.edu

Our goal was to quantitate inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) binding to aldolase C tetramer (aldolase4) and its displacement by inositol 1,3,4-trisphosphate (Ins(1,3,4)P3) under conditions which approximated the in vivo state. Anions were found to have major effects. Decreasing [KCl] from 100 to 10mM, at 0 degrees C and pH 7.0, increased maximal Ins(1,4,5)P3 binding to 1.0 to 2.4mol per mol aldolase4. At 10 and 30mEq/l [Cl-], an additional high affinity site was detected (Kds = 0.43 and 0.86 microM, respectively). Increasing concentrations of other anions (SO42-, propanoate-, HCO3-, acetate-) also inhibited binding, but effects would be minimal at concentrations of these anions present in the cytoplasm of living cells. Ins(1,3,4)P3 displacement of aldolase C-bound Ins(1,4,5)P3 was sensitive to [Cl-]; at 30mEq/l [Cl-] and 37 degrees C, Ins(1,3,4)P3 released 20% of bound Ins(1,4,5)P3 at concentrations of 100nM. Changing temperature from 0 to 37 degrees C increased Kds for Ins(1,4,5)P3 binding. Changes in free [Ca2+], [Mg2+], [Na+] and [K+] and changes in osmolality had no effect on Ins(1,4,5)P3 binding to aldolase C. In vivo Ins(1,4,5)P3-aldolase4 binding at 30mEq/l [Cl-] and 37 degrees C were calculated for different [Ins(1,4,5)P3]free over the range 0.2 to 1.0 microM. For different cytoplasmic [Ins(1,4,5)P3]free. Ins(1,4,5)P3 binding to aldolase4 was sufficient, if acutely released, to nearly double cytoplasmic [Ins(1,4,5)P3]free. We proposed a schema whereby release of aldolase C-bound Ins(1,4,5)P3 evoked by Ins(1,3,4)P3 amplifies effects of phospholipase C-formed Ins(1,4,5)P3.

UI	MeSH Term	Description	Entries
D007295	Inositol Phosphates	Phosphoric acid esters of inositol. They include mono- and polyphosphoric acid esters, with the exception of inositol hexaphosphate which is PHYTIC ACID.	Inositol Phosphate,Phosphate, Inositol,Phosphates, Inositol
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D009130	Muscle, Smooth	Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)	Muscle, Involuntary,Smooth Muscle,Involuntary Muscle,Involuntary Muscles,Muscles, Involuntary,Muscles, Smooth,Smooth Muscles
D010710	Phosphates	Inorganic salts of phosphoric acid.	Inorganic Phosphate,Phosphates, Inorganic,Inorganic Phosphates,Orthophosphate,Phosphate,Phosphate, Inorganic
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D011189	Potassium Chloride	A white crystal or crystalline powder used in BUFFERS; FERTILIZERS; and EXPLOSIVES. It can be used to replenish ELECTROLYTES and restore WATER-ELECTROLYTE BALANCE in treating HYPOKALEMIA.	Slow-K,Chloride, Potassium
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D002254	Carbonates	Salts or ions of the theoretical carbonic acid, containing the radical CO2(3-). Carbonates are readily decomposed by acids. The carbonates of the alkali metals are water-soluble; all others are insoluble. (From Grant & Hackh's Chemical Dictionary, 5th ed)	Carbonate
D003593	Cytoplasm	The part of a cell that contains the CYTOSOL and small structures excluding the CELL NUCLEUS; MITOCHONDRIA; and large VACUOLES. (Glick, Glossary of Biochemistry and Molecular Biology, 1990)	Protoplasm,Cytoplasms,Protoplasms
D005634	Fructose-Bisphosphate Aldolase	An enzyme of the lyase class that catalyzes the cleavage of fructose 1,6-biphosphate to form dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. The enzyme also acts on (3S,4R)-ketose 1-phosphates. The yeast and bacterial enzymes are zinc proteins. (Enzyme Nomenclature, 1992) E.C. 4.1.2.13.	Aldolase,Fructosediphosphate Aldolase,Aldolase A,Aldolase B,Aldolase C,Fructose 1,6-Bisphosphate Aldolase,Fructose 1,6-Bisphosphate Aldolase, Class II,Fructose 1-Phosphate Aldolase,Fructose Biphosphate Aldolase,Fructosemonophosphate Aldolase,1,6-Bisphosphate Aldolase, Fructose,Aldolase, Fructose 1,6-Bisphosphate,Aldolase, Fructose 1-Phosphate,Aldolase, Fructose Biphosphate,Aldolase, Fructose-Bisphosphate,Aldolase, Fructosediphosphate,Aldolase, Fructosemonophosphate,Fructose 1 Phosphate Aldolase,Fructose 1,6 Bisphosphate Aldolase,Fructose Bisphosphate Aldolase