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 masses of inositol phosphates have been determined in isolated skeletal muscles from Xenopus laevis (sartorius, tibialis anterior and iliofibularis) and rat (gastrocnemius and soleus) which were quick-frozen in the resting state and at different stages of an isometric (Xenopus) or isotonic (rat) tetanus. The isomeric spectrum of inositol phosphates detected was similar to that in other tissues and cell types. The total sarcoplasmic concentrations of the isomers Ins-(1,4,5,6)P4/Ins(3,4,5,6)P4 (0.2-0.9 microM), Ins(1,3,4,6)P4 (not detectable), Ins(1,3,4,5,6)P5 (about 1 microM) and InsP6 (3.2-4.6 microM) were lower than in other cell types. Variations in these concentrations were due to the muscle type rather than to the donor species. The putative second messenger Ins(1,4,5)P3, as well as its dephosphorylation product Ins(1,4)P2, were present at surprisingly high total myoplasmic resting concentrations, ranging from 1.2 to 2.5 microM and 3.5 to 6.9 microM respectively. Upon tetanic stimulation these two inositol phosphates in particular exhibited significantly increased total sarcoplasmic concentrations, up to 4.2 microM and 11.3 microM respectively, with a time scale of seconds. From the initial rate of increase in the total sarcoplasmic concentrations of Ins(1,4,5)P3 and its rapidly formed metabolic products, a minimal phosphoinositidase C (PIC) activity in tetanically activated Xenopus skeletal muscle of about 1.7-2.6 microM/s can be estimated. This PIC activity observed in vivo seems to be far too low to account for a functional role for Ins(1,4,5)P3 as a chemical transmitter in the fast excitation-contraction coupling (ECC) process in skeletal muscle. The presence of Ins(1,3,4,5)P4 in all muscle types is indicative of a Ca(2+)-activated Ins(1,4,5)P3 3-kinase activity. The rapid transient increases in Ins(1,3,4)P3 and Ins(1,3)P2 in isometrically contracting Xenopus muscles suggest that corresponding Ins(1,3,4,5)P4 phosphatases are operating in skeletal muscle as well. In all muscles investigated except rat soleus, the fructose 1,6-bisphosphate [Fru(1,6)P2] concentration increased substantially during a tetanus, up to about 2 mM. This increase is correlated with a simultaneous decrease in phosphocreatine, whereas the energy charge of the muscles was essentially unaffected by the applied tetani. The time course of the rise in Fru(1,6)P2 was used to model changes in the free concentrations of high-affinity aldolase-binding inositol phosphates during the course of a tetanus. These calculations demonstrate that the free concentration of Ins(1,4,5)P3 and other aldolase-bound inositol phosphates can increase much faster and to a larger extent than the corresponding total concentrations as a result of their competitive displacement from aldolase-binding sites by the rapidly rising concentration of Fru(1,6)P2.
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PMID:Masses of inositol phosphates in resting and tetanically stimulated vertebrate skeletal muscles. 176 26

While the equilibrium assumption and the validity of using total measured concentrations for near equilibrium indicator reactions have been widely tested in liver, these have not been systematically evaluated in skeletal muscle. Vascularly isolated dog gracilis muscles were stimulated via the nerve at 4 Hz, and tissue was sampled by quick freezing at rest and after 10, 15, 30, 60, and 180 s of stimulation or after stimulation in the presence of glycolytic blockade by iodoacetate. Phosphocreatine, creatine, and several glycolytic intermediates were measured in tissue extracts. The in vivo mass action ratios for triosephosphate isomerase and aldolase were evaluated relative to substrate concentrations and compared with equilibrium constants determined in vitro. Although there was evidence of substrate binding at low substrate levels for the triosephosphate isomerase reaction, the in vivo mass action ratios for both reactions stabilized at a constant value at moderate substrate levels and in glycolytically blocked muscles. It was concluded that both enzymes are in apparent equilibrium in vivo, but the equilibrium constants are lower than those determined in vitro. The mass action ratios of the combined creatine kinase, lactate dehydrogenase, glyceraldehyde-phosphate dehydrogenase and phosphoglycerate kinase reactions were determined for resting muscles. These reactions are also at equilibrium and the equilibrium constants are consistent with in vitro values.
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PMID:In vivo glycolytic equilibria in dog gracilis muscle. 397 26

The present work describes procedures in which seven major muscle enzymes and serum albumin can be simultaneously isolated from chicken skeletal muscles. The seven enzymes isolated were: phosphorylase, enolase, creatine-P kinase, aldolase, glyceraldehyde-3-P dehydrogenase, phosphoglycerate mutase, and triose-P isomerase. The proteins isolated by these methods were judged to be greater than 97% pure on the basis of electrophoretic analysis in sodium dodecyl sulfate polyacrylamide gels. The procedure is applicable for isolation of the enzymes from large (greater than 100 g) or small (less than 0.5 g) amounts of muscle tissue and the entire procedure can be completed within two days. Particularly useful features of the procedures are: (1) preferential solubilization of the enzymes from myofibrils by extraction of muscle specimens in solutions of different ionic strength; (2) specific precipitation of phosphorylase, creatine-P kinase, and glyceraldehyde 3-Phosphate dehydrogenase from solutions of specified pH and degrees of ammonium sulfate saturation; and (3) an alternate method for isolation of glyceraldehyde-3-P dehydrogenase by specific elution of the enzyme from phosphocellulose columns with ATP. Because of the ease, rapidity, and reproducibility of the procedures, these methods may be useful for the routine isolation of the muscle enzymes in studies on biochemical regulation, as well as for obtaining large quantitites of the enzymes for structural analysis.
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PMID:A simple procedure for the isolation of seven abundant muscle enzymes. 626 Dec 32

It has been well documented that neural information, or the consequences of it, is required for the full phenotypic expression of different skeletal muscle fiber types. In the present work, we investigate the effect of removal of neural information, via surgical denervation, on the levels and rates of synthesis of several enzyme in mature breast ("fast-twitch") "white" muscle fibers of the chicken. Denervation of these muscles resulted in reductions in the concentrations of several glycolytic enzymes to new steady state levels which were only about 50% of normal, and these decreases in enzyme levels were completed within 2 weeks after severing the nerves. In contrast, denervation for as long as 6 weeks did not have a significant effect on the levels of creatine-P kinase molecules in this muscle type. The decreased level of the skeletal muscle-specific aldolase A4 isoenzyme in denervated breast muscle fibers was associated with a 2- to 3-fold reduction in the relative rate of synthesis of this enzyme following denervation. As expected, denervation had no appreciable effect on the relative rate of synthesis of the muscle-specific MM isoenzyme of creatine-P kinase in this muscle. Our results show that neural information, or the consequences of it, is required to maintain the levels and rates of synthesis of glycolytic enzymes but not of creatine-P kinase in mature fast-twitch muscle fibers. We suggest that denervation results in a partial "dedifferentiation" of these fibers.
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PMID:Effect of denervation on the levels and rates of synthesis of specific enzymes in "fast-twitch" (breast) muscle fibers of the chicken. 724 Feb 16