Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Foetal and adult liver 6-phosphofructo-2-kinase (PFK-2) were purified by identical protocols. The native molecular masses of both enzymes were determined by gel filtration and were 89.1 and 100.0 kDa respectively. No differences were found in SDS/PAGE in 10%-acrylamide gel (55 kDa per subunit). The kinetic properties displayed by both enzymes were similar, except for the sensitivity to inhibition by sn-glycerol 3-phosphate. Foetal PFK-2 was a good substrate for phosphorylation by cyclic AMP-dependent protein kinase and protein kinase C, whereas the adult enzyme was phosphorylated only by cyclic AMP-dependent protein kinase. However, the phosphorylation affected only the kinetic properties of the adult enzyme, suggesting the presence in both enzymes of different sites of phosphorylation by cyclic AMP-dependent protein kinase. These differences in primary structure were consistent with the distinct chromatographic profiles of the phosphopeptides after digestion of the protein with CNBr. Western-blot analysis with antibodies specific for the N-terminal region of the liver-type PFK-2 poorly recognized the foetal enzyme, suggesting that both enzymes differ at least in the N-terminal sequence.
 ...
PMID:Characterization of 6-phosphofructo-2-kinase from foetal-rat liver. 131 May 98

Bovine brain 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase was purified to homogeneity and characterized. This bifunctional enzyme is a homodimer with a subunit molecular weight of 120,000, which is twice that of all other known bifunctional enzyme isozymes. The kinase/bisphosphatase activity ratio was 3.0. The Km values for fructose 6-phosphate and ATP of the 6-phosphofructo-2-kinase were 27 and 55 microM, respectively. The Km for fructose 2,6-bisphosphate and the Ki for fructose 6-phosphate for the bisphosphatase were 70 and 20 microM, respectively. Physiologic concentrations of citrate had reciprocal effects on the enzyme's activities, i.e. inhibiting the kinase (Ki of 35 microM) and activating the bisphosphatase (Ka of 16 microM). Phosphorylation of the brain enzyme was catalyzed by the cyclic AMP-dependent protein kinase with a stoichiometry of 0.9 mol of phosphate/mol of subunit and at a rate similar to that seen with the liver isozyme. In contrast to the liver isozyme, the kinetic properties of the brain enzyme were unaffected by cyclic AMP-dependent protein kinase phosphorylation, and also was not a substrate for protein kinase C. The brain isozyme formed a labeled phosphoenzyme intermediate and cross-reacted with antibodies raised against the liver isozyme. However, the NH2-terminal amino acid sequence of a peptide generated by cyanogen bromide cleavage of the enzyme had no identity with any known bifunctional enzyme sequences. These results indicate that a novel isozyme, which is related to other 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase isozymes, is expressed specifically in neural tissues.
 ...
PMID:Bovine brain 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase. Evidence for a neural-specific isozyme. 132 53

The concentration of fructose 2,6-bisphosphate in the brain remained stable during starvation and early stages of ischaemia, but decreased in diabetes or after lengthened ischaemia. 6-Phosphofructo-1-kinase activity was also decreased in diabetic and ischaemic animals, whereas 6-phosphofructo-2-kinase was not modified. The concentration of the bisphosphorylated metabolite seems to be remarkably constant under a wide variety of experimental conditions, suggesting that it plays an essential role in the basal activation of 6-phosphofructo-1-kinase. Purified 6-phosphofructo-2-kinase also showed fructose-2,6-bisphosphatase activity with an activity ratio similar to that of the purified heart isoenzyme. The brain enzyme also has a net charge similar to that of the heart isoenzyme. Its activity is not modified by sn-glycerol 3-phosphate, and it is more sensitive to citrate than the liver or muscle isoenzyme. Moreover, the enzyme from brain, similarly to that from heart and muscle, is not modified by the cyclic AMP-dependent protein kinase or protein kinase C. A near-full-length cDNA probe from liver hybridized with RNA from brain and heart. In both cases, a major band of 6.8 kb of RNA and a minor one of 4 kb of RNA were detected. All these properties support the hypothesis that brain contains a different isoenzymic form from that of liver and muscle, and it is probably related to the heart isoform.
 ...
PMID:6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase in rat brain. 164 1

We have shown previously that bovine heart fructose-6-phosphate 2-kinase/fructose-2,6-bisphosphatase (EC 2.7.1.105/3.1.3.46) is phosphorylated by cAMP-dependent protein kinase and protein kinase C; phosphorylation results in activation of kinase. This activation of heart enzyme is in contrast to results with the liver isozyme, in which phosphorylation by cAMP-dependent protein kinase inhibits the kinase activity. As an initial step toward understanding this difference between the isozymes we have determined the DNA sequence of the heart enzyme and analyzed the amino acid sequence with special emphasis on the location of the phosphorylation site. We isolated and sequenced two overlapping cDNA fragments, which together could encode the complete amino acid sequence of bovine heart fructose-6-phosphate 2-kinase/fructose-2,6-bisphosphatase, a protein of 530 amino acids, with a calculated molecular weight of 60,679. Since the deduced protein contained amino acid sequences identical to the sequences of four known tryptic peptides from this enzyme we concluded that the deduced protein sequence did represent bovine heart enzyme. In addition, a cDNA fragment hybridized to a 4-kilobase mRNA from bovine heart. The phosphorylation sites of the heart enzyme were located near the C terminus, whereas the phosphorylation site of the liver isozyme is known to be located near the N terminus. These opposite locations of the phosphorylation sites may explain the contrasting effect of the covalent modification on the enzymes' activities.
 ...
PMID:Bovine heart fructose-6-phosphate 2-kinase/fructose-2,6-bisphosphatase: complete amino acid sequence and localization of phosphorylation sites. 216 12

Incubation of chicken embryo fibroblasts with mitogenic concentrations of insulin for 24 hr or with the tumor promoter phorbol 12-myristate 13-acetate for 6 hr stimulated lactate release and 3-O-methylglucose uptake. Insulin also increased the Vmax of 6-phosphofructo-1-kinase (ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11). Both agents increased the concentration of fructose 2,6-bisphosphate and the activity of 6-phosphofructo-2-kinase (EC 2.7.1.-), the enzyme that catalyzes the synthesis of this stimulator of 6-phosphofructo-1-kinase. These changes provide an explanation for the stimulation of glycolysis by insulin and phorbol esters. In contrast to the situation in rat liver, fructose 2,6-bisphosphate concentration did not decrease after cyclic AMP treatment. Incubation of cells with phorbol ester analogues or with glycerol derivatives that are known to stimulate, or to bind to, protein kinase C did increase the concentration of fructose 2,6-bisphosphate, suggesting that the stimulation of 6-phosphofructo-2-kinase by phorbol 12-myristate 13-acetate is mediated by protein kinase C.
 ...
PMID:Phorbol 12-myristate 13-acetate and insulin increase the concentration of fructose 2,6-bisphosphate and stimulate glycolysis in chicken embryo fibroblasts. 293 20

The concentration of fructose 2,6-bisphosphate and the activity of 6-phosphofructo-2-kinase are increased after infection of chick-embryo fibroblasts with the Rous sarcoma virus, or with a temperature-sensitive mutant of this virus at the permissive, but not at the non-permissive, temperature. This is observed after transformation by retroviruses carrying either the v-src or v-fps, but not the v-mil and/or v-myc, oncogenes. Comparison of the effects of the Rous sarcoma virus with those of phorbol myristate acetate on fructose 2,6-bisphosphate suggests that both result from the stimulation of a step which is rate-limiting for 6-phosphofructo-2-kinase activation and which is also controlled by protein kinase C.
 ...
PMID:Expression of the v-src or v-fps oncogene increases fructose 2,6-bisphosphate in chick-embryo fibroblasts. Novel mechanism for the stimulation of glycolysis by retroviruses. 294 13

Purified bovine heart 6-phosphofructo-2-kinase can be phosphorylated in the presence of protein kinase C and dephosphorylated by alkaline phosphatase; changes in phosphorylation state have no effect on enzyme activity. By contrast, the rat liver enzyme is a poor substrate for protein kinase C. Unlike the liver enzyme, which is bifunctional and is phosphorylated by fructose 2,6-[2-32P]bisphosphate, the heart enzyme contains 10 times less fructose 2,6-bisphosphatase activity and is phosphorylated at a slower rate and to a lesser extent than the liver enzyme. Both rat liver and bovine heart enzymes catalyse a similar exchange reaction between [U-14C]ADP and ATP.
 ...
PMID:Phosphorylation of purified bovine heart and rat liver 6-phosphofructo-2-kinase by protein kinase C and comparison of the fructose-2,6-bisphosphatase activity of the two enzymes. 303 Feb 81

Changes in glycolytic flux have been observed in liver under conditions where effects of cAMP seem unlikely. We have, therefore, studied the phosphorylation of four enzymes involved in the regulation of glycolysis and gluconeogenesis (6-phosphofructo-1-kinase from rat liver and rabbit muscle; pyruvate kinase, 6-phosphofructo-2-kinase and fructose-1,6-bisphosphatase from rat liver) by defined concentrations of two cAMP-independent protein kinases: Ca2+/calmodulin-dependent protein kinase and Ca2+/phospholipid-dependent protein kinase (protein kinase C). The results were compared with those obtained with the catalytic subunit of cAMP-dependent protein kinase. The following results were obtained. 1. Ca2+/calmodulin-dependent protein kinase phosphorylates 6-phosphofructo-1-kinase and L-type pyruvate kinase at a slightly lower rate as compared to cAMP-dependent protein kinase. 2. 6-Phosphofructo-1-kinase is phosphorylated by the two kinases at a single identical position. There is no additive phosphorylation. The final stoichiometry is 2 mol phosphate/mol tetramer. The same holds for L-type pyruvate kinase except that the stoichiometry with either kinase or both kinases together is 4 mol phosphate/mol tetramer. 3. Rabbit muscle 6-phosphofructo-1-kinase is phosphorylated by cAMP-dependent protein kinase but not by Ca2+/calmodulin-dependent protein kinase. 4. Fructose-1,6-bisphosphatase from rat but not from rabbit liver is phosphorylated at the same position but at a markedly lower rate by Ca2+/calmodulin-dependent protein kinase when compared to the phosphorylation by cAMP-dependent protein kinase. 5. 6-Phosphofructo-2-kinase is phosphorylated by Ca2+/calmodulin-dependent protein kinase only at a negligible rate. 6. Protein kinase C does not seem to be involved in the regulation of the enzymes examined: only 6-phosphofructo-2-kinase became phosphorylated to a significant degree. In contrast to the phosphorylation by cAMP-dependent protein kinase, this phosphorylation is not associated with a change of enzyme activity. This agrees with our observation that the sites of phosphorylation by the two kinases are different. The results indicate that Ca2+/calmodulin-dependent protein kinase but not protein kinase C could be involved in the regulation of hepatic glycolytic flux under conditions where changes in the activity of cAMP-dependent protein kinase seem unlikely.
 ...
PMID:Are calcium-dependent protein kinases involved in the regulation of glycolytic/gluconeogenetic enzymes? Studies with Ca2+/calmodulin-dependent protein kinase and protein kinase C. 304 Apr 8

Bradykinin (BK), a peptide released during inflammatory response, has been investigated for its ability to regulate glucose metabolism in human fibroblasts. The peptide is able to significantly increase glycolytic flux in these cells. The strict relationship between the glycolytic rate and the levels of fructose 2,6-bisphosphate (Fru-2,6-P2) strongly suggests that the metabolite plays a key role in the regulation of glucose metabolism by bradykinin. The mechanism by which bradykinin increases Fru-2,6-P2 content involves the activation of 6-phosphofructo-2-kinase (PFK-2), the enzyme responsible for the synthesis of the metabolite. The study of the multiple signalling systems triggered by bradykinin demonstrates the involvement of the rise in intracellular Ca2+ concentration and of protein kinase C mediated pathway in the mechanism by which bradykinin increases Fru-2,6-P2 content and PFK-2 activity.
 ...
PMID:Bradykinin stimulates fructose 2,6-bisphosphate metabolism in human fibroblasts. 816 44

The mitogenic signals that control fructose 2,6-bisphosphate metabolism in murine Swiss 3T3 fibroblasts have been studied. Bombesin, vasopressin, insulin, protein kinase C activation by phorbol esters, or increase in the intracellular cAMP concentration by forskolin induced an increase in fructose 2,6-bisphosphate levels. When the cells were incubated in the presence of insulin or phorbol esters, an increase in the Vmax of 6-phosphofructo-2-kinase activity was observed. However, forskolin did not produce this effect. The increase in 6-phosphofructo-2-kinase activity elicited by phorbol 12,13-dibutyrate was blocked by cycloheximide. In contrast, the effect of insulin did not require protein synthesis. This study demonstrates that different mitogenic signal transduction pathways control the levels of fructose 2,6-bisphosphate. The high rate of glycolysis in proliferating Swiss 3T3 cells may be explained by an increase in the levels of this regulatory metabolite.
 ...
PMID:Control of fructose 2,6-bisphosphate metabolism by different mitogenic signals in Swiss 3T3 fibroblasts. 817 46


1 2 Next >>