Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.2.13 (aldolase)
 3,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), which has been hypothesized to be a chemical transmitter in excitation-contraction coupling in skeletal muscle, on aldolase bound to isolated triad junctions were investigated. Fructose-1,6-bisphosphate aldolase was identified as the major specific binding protein for the Ins(1,4,5)P3 analogue glycolaldehyde (2)-1-phospho-D-myo-inositol 4,5-bisphosphate which can form covalent bonds with protein amino groups by reduction of the Schiff's base intermediate with [3H]NaCNBH3. This analogue, Ins(1,4,5) P3, and the inositol polyphosphates inositol 1,3,4,5-tetrakisphosphate and inositol 1,4-bisphosphate were nearly equipotent in selectively releasing membrane bound aldolase with a K0.5 of about 3 microM. The rank order of the K0.5 values was identical to the KI values for inhibition of aldolase. Aldolase was also released by its substrate fructose 1,6-bisphosphate and by 2,3-bisphosphoglycerate. Ins(1,4,5)P3-induced aldolase release did not disrupt the triad junction; glyceraldehyde-3-phosphate dehydrogenase, a known junctional constituent, was displaced only at much higher Ins(1,4,5)P3 concentrations. Ins(1,4,5)P3 was as effective as fructose 1,6-bisphosphate in releasing aldolase from myofibrils. A finite number of binding sites for aldolase exist on triads (Bmax = 43-47 pmol of tetrameric aldolase exist on triads (Bmax = 43-47 pmol of tetrameric aldolase/mg of triad protein, KD = 23 nM). The junctional foot protein was implicated as an aldolase binding site by affinity chromatography with the junctional foot protein immobilized on Sepharose 4B. The potential consequences of aldolase being bound in the gap between the terminal cisternae and the transverse tubule to inositol polyphosphate and glycolytic metabolism in that local region are discussed.
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PMID:Inositol polyphosphate-mediated repartitioning of aldolase in skeletal muscle triads and myofibrils. 278 11

A search for target proteins of inositol polyphosphates in mammalian tissues revealed that fructose 1,6-bisphosphate aldolases are potent isomer-selective binders of inositol polyphosphates. Binding was measured by tryptophan fluorescence quenching, by difference spectroscopy, and, in aldolase A, by equilibrium dialysis. Among a series of inositol phosphates containing between one and six phosphates and varying in their positions, inositol 1,4,5-trisphosphate was found to be bound strongest both by aldolase A [( L]0.5 = 0.58 microM) and aldolase B [( L]0.5 = 0.83 microM). Aldolase A showed also a strong binding of inositol tetrakisphosphate [( L]0.5 = 0.83 microM), of inositol 2,4,5-trisphosphate [( L]0.5 = 1.4 microM) and of inositol 1,3,4,5,6-pentakisphosphate [( L]0.5 = 2.0 microM); in aldolase B but not in aldolase A inositol 4,5-bisphosphate was bound as strongly as inositol 1,4,5-trisphosphate [( L]0.5 = 0.95 microM) and also inositol 2,4,5-trisphosphate was tightly bound [( L]0.5 = 1.2 microM). Both in aldolase A and B, 4 mol inositol 1,4,5-trisphosphate were bound/mol tetramer, in aldolase A a total binding of 8 mol inositol 1,4-bisphosphate/mol tetramer was evaluated. Difference spectra revealed that the binding of inositol phosphates to both isoenzymes may be associated with conformational changes. The binding of all inositol phosphates led to an inhibition of the enzyme activity. In aldolase A the inhibition was purely competitive, in aldolase B a complex cooperative type of inhibition was evident with fructose 1,6-bisphosphate as a substrate whereas with fructose 1-phosphate the inhibition also was purely competitive. Model calculations based on the in vitro data indicated a significant potential of aldolase to bind preferentially inositol 1,4,5-trisphosphate also in the presence of excess fructose 1,6-bisphosphate.
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PMID:Mammalian aldolases are isomer-selective high-affinity inositol polyphosphate binders. 378 Jul 51

A cytoskeletal fraction of porcine tracheal smooth muscle (PTSM) was found to contain > 90% of total cellular aldolase (fructose 1,6-bisphosphate aldolase, EC 4.1.2.13) activity. PTSM aldolase was purified by DEAE and inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) affinity chromatography and found to react with an antibody directed against human aldolase C, but not anti-aldolase A and B. The molecular mass of native aldolase was about 138 kDa (on Sephacryl S-300); SDS-denatured enzyme was 35 kDa (comigrated with rabbit skeletal muscle aldolase). Total cellular aldolase tetramer (aldolase4) content was 34.5 pmol/100 nmol lipid P(i). Ins(1,4,5)P3) binding activity coeluted with aldolase during Sephacryl 300, DEAE, and Ins(1,4,5)P3 affinity chromatography. Ins(1,4,5)P3 bound to purified aldolase (at 0 degree C) in a dose-dependent manner over the range [Ins(1,4,5)P3] 20 nM to 20 microM, with maximal binding of 1 mol of Ins(1,4,5)P3/mol aldolase4 and a Kd of 12-14 microM. Fru(1,6)P2 and Fru(2,6)P2 displaced bound Ins(1,4,5)P3) with a 50% inhibition at 30 and 170 microM, respectively. Ins(1,3,4)P3 (20 microM) and glyceraldehyde 3-phosphate (2 mM) were also potent inhibitors of Ins(1,4,5)P3 binding, but not inositol 4-phosphate or inositol 1,4-bisphosphate (20 microM each). Aldolase-bound Ins(1,4,5)P3 may play a role in phospholipase C-independent increases in free [Ins(1,4,5)P3].
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PMID:Inositol 1,4,5-trisphosphate binding to porcine tracheal smooth muscle aldolase. 765 22