Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sarcoplasmic reticulum fragments isolated from dog cardiac muscle possess a calcium-accumulating system associated with a series of enzymes linked to glycogenolysis. These enzymes include: adenylate cyclase, cyclic AMP-dependent protein kinase, phosphorylase b kinase, phosphorylase (b/a, 30/1),"debrancher" enzyme, and glycogen (0.3 to 0.7 mg/mg of protein). The sarcoplasmic reticulum preparation produced glucose 1-phosphate and glucose from either endogenous or exogenous glycogen. Both the calcium-accumulating and glycogenolytic enzymes sediment in a single peak at 33% sucrose on a linear continous sucrose density gradient, and the complex remains intact throughout repeated washing. Glycogen particles appear to be associated with the sarcoplasmic reticulum in situ as well as in the isolated microsomal fraction. The sarcoplasmic reticulum-glycogenolytic complex, monitored by a linked enzyme spectrophotometric assay, shows several features: (a) activation of phosphorylase activity to peak rate occurs over a very rapid time course which cannot be duplicated using combinations of purified enzymes; (b) activation is inhibited by protein kinase inhibitor; (c) phosphorylase b functions as in the purified form with respect to AMP (Km, 0.3 mM); (d) in the presence of limiting amounts of glycogen, optimal phosphorylase b activity in the sarcoplasmic reticulum requires the presence of debrancher, and the activity is sensitive to inhibitors of that enzyme such as Tris, which suggests the possiblity that the enzymes bear a specific structual relationship to the glycogen present. Phosphorylase b leads to a activation in the sarcoplasmic reticulum was completely resistant to ethylene glycol bis(beta-aminoethyl either)-N,N'-tetraacetic acid (EGTA). Inhibition of calcium accumulation by or release of bound calcium from sarcoplasmic reticulum by X537A (RO 2-2985) did not alter the EGTA resistance. These results suggest that cardiac sarcoplasmic reticulum is a complex organelle containing functions that may be related to excitation-contraction coupling and intermediary metabolism.
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PMID:Association of gylcogenolysis with cardiac sarcoplasmic reticulum. 0 55

Autoactivation of phosphorylase kinase in the presence of substrates has been studied to determine the cause of the hysteresis, or lag, in the phosphorylase kinase reaction. Peptide analogs corresponding to the convertible serine region of phosphorylase have been used as low molecular weight alternative substrates. Autophosphorylation of the kinase molecule was measured under conditions that favored autoactivation. Phosphorylase b and a tetradecapeptide, which was found to be a good model of phosphorylase, stimulated autoactivation by 86- and 37-fold, respectively. The tetradecapeptide also stimulated autophosphorylation of subunits A and B of the kinase molecule. This increased autophosphorylation coincided with an increased ability to convert phosphorylase. This finding supports the hypothesis that autophosphorylation is responsible for the lag in the phosphorylase kinase reaction. No evidence was obtained to suggest that the lag could be due to dissociation of the kinase. The stoichiometry of phosphate incorporation into phosphorylase kinase subunits by autophosphorylation was much greater than that reported to occur by protein kinase phosphorylation. Multiple phosphorylation sites in subunit A accounted for most of the phosphate incorporation during autophosphorylation. Saturating levels of hexa- and octapeptide analogs also caused stimulation of autophosphorylation. Possible mechanisms and experimental implications of substrate-stimulated autophosphorylation are discussed. Consideration also is given to the possible role of effectors in autophosphorylation in vivo.
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PMID:Stimulation of phosphorylase kinase autophosphorylation by peptide analogs of phosphorylase. 100 97

Calcium plus calmodulin (Ca2+/CaM)-dependent protein kinase activity was demonstrated in subcellular fractions from Torpedo californica electric organ. A protein kinase activity dependent on Ca2+/CaM was purified about 200-fold from electric organ cytosol using DEAE-cellulose and CaM-affinity chromatography. The most effective exogenous substrates for this enzyme were the synapse-specific protein Synapsin I (Protein I) and histone f3. Phosphorylase b, skeletal muscle myosin light chains, casein, phosvitin, histone f2b, and G-substrate were relatively poorly phosphorylated by Torpedo CaM-protein kinase. Thus, the enzyme differs in its substrate specificity from known cyclic nucleotide-dependent protein kinases, myosin light chain kinase and phosphorylase kinase. The Km for ATP was 15-20 microM; for Synapsin I, 0.8 microM; and for CaM, 85 nM. Two major endogenous substrates (Mr = 62,000 and 54,000) for CaM-protein kinase co-purified with the enzyme through the CaM-affinity column step. These two substrates, as well as the enzyme, were present in other subcellular fractions in addition to the cytosol, including crude membranes and purified synaptic vesicles. A third major substrate (Mr = 39,000) could be separated from the enzyme during purification and appeared to be localized primarily in the cytosol. CaM-protein kinase increased the phosphorylation of both serine and threonine residues in endogenous substrates. In contrast to previous reports, no evidence for Ca2+/CaM-dependent phosphorylation of any subunit of the acetylcholine receptor was obtained.
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PMID:Calmodulin-dependent protein kinase and associated substrates in Torpedo electric organ. 687 98