Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several glycolytic enzymes were observed to have between 40-90% of their activities associated with the particulate fractions of lysed nerve endings. The enzymes showing high particulate activity in lysed nerve endings were hexokinase (EC 2.7.1.1), aldolase (EC 4.1.2.13), glucosephosphate isomerase (EC 5.3.1.9), phosphofructokinase (EC 2.7.1.11), glyceraldehyde-phosphate dehydrogenase (EC 1.2.1.12), pyruvate kinase (EC 2.7.1.40) and lactate dehydrogenase (EC 1.1.27). With the exception of phosphofructokinase, 80% or more of the particle associated activity of each enzyme was solubilized by salt treatment indicating the association with particles was ionic. Sub-fractionation of lysed nerve endings showed hexokinase and fumarase (EC 4.2.1.2) had the highest specific activity in the same fractions which is consistent with observations indicating that hexokinase is associated with mitochondria. The other glycolytic zymes having high particulate activity, aldolase, glucosephosphate isomerase, phosphofructokinase, glyceraldehyde-phosphate dehydrogenase, pyruvate kinase and lactate dehydrogenase, showed enrichment in fractions containing synaptosomal membranes, i.e. the fractions having highest specific activity of acetylcholinesterase (EC 3.1.1.7) and (Na+ + K+)-ATPase (EC 3.6.1.3).
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PMID:Association of glycolytic enzymes with particulate fractions from nerve endings. 62 35

A second NF1 messenger differing in the GAP domain was recently described. This type II transcript contains an internal additional sequence consisting of an open reading frame, in phase with the preceding and the following sequences and predicts a 21 amino acid addition in the catalytic domain of NF1 protein. In this report we present analysis of the two forms of NF1 transcripts in several normal human tissues and in primary neurofibromatosis tumors. Our results indicate (i) that the type II NF1 messenger displaying the additional exon is very widely expressed in all the normal adult tissues tested, (ii) that it is the form of NF1 messenger expressed in peripheral nerve and neurofibromas, and (iii) that the additional sequence could encode for a peptide related to a nucleoside triphosphatase.
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PMID:The neurofibromatosis 1 gene transcripts expressed in peripheral nerve and neurofibromas bear the additional exon located in the GAP domain. 128 Jan 27

A variety of systems use nucleoside triphosphate hydrolysis to control or provide energy for biological processes, mediated through protein-protein interactions. The nature of this coupling may vary, but often there is a degree of similarity. In this paper, two systems are compared: actomyosin in muscle and p21ras in a signal transduction pathway as yet undefined. The mechanism of the nucleotide triphosphate hydrolysis and the consequent changes in the protein-nucleotide complex have been investigated, to understand how the coupling to biological function is achieved. The basal nucleoside triphosphatase mechanisms are compared and the roles of proteins that activate the hydrolysis, actin and GAP, are discussed. The cleavage process was probed by stereochemical techniques to determine the basic mechanism, of either a phosphorylated enzyme intermediate or direct displacement of nucleoside diphosphate by water. Phosphate-water oxygen exchange probes were used to investigate nucleoside triphosphate and inorganic phosphate release steps. A new method of probing the kinetics of inorganic phosphate release directly has been developed. In muscle, this process seems likely to be related directly to force generation. In the GAP-ras system, measurement of phosphate release is allowing the mechanism of the GAP-p21ras interaction to be probed.
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PMID:The role of nucleoside triphosphate hydrolysis in transducing systems: p21ras and muscle. 135 Dec 91

Two distinct GAPs of 120 and 235 kDa called GAP1 and NF1 serve as attenuators of Ras, a member of GTP-dependent signal transducers, by stimulating its intrinsic guanosine triphosphatase (GTPase) activity. The GAP1 (also called Ras GAP) is highly specific for Ras and does not stimulate the intrinsic GTPase activity of Rap1 or Rho. Using GAP1C, the C-terminal GTPase activating domain (residues 720-1044) of bovine GAP1, we have shown previously that the GAP1 specificity is determined by the Ras domain (residues 61-65) where Gln61 plays the primary role. The corresponding domain (residues 1175-1531) of human NF1 (called NF1C), which shares only 26% sequence identity with the GAP1C, also activates Ras GTPases. In this article, we demonstrate that the NF1C, like the GAP1C, is highly specific for Ras and does not activate either Rap1 or Rho GTPases. Furthermore, using a series of chimeric Ras/Rap1 and mutated Ras GTPases, we show that Gln at position 61 of the GTPases primarily determines that NF1C as well as GAP1C activates Ras GTPases, but not Rap1 GTPases, and Glu at position 63 of the GTPases is required for maximizing the sensitivity of Ras GTPases to both NF1C and GAP1C. Interestingly, replacement of Glu63 of c-HaRas by Lys reduces its intrinsic GTPase activity and abolishes the GTPase activation by both NF1C and GAP1C. Thus, the potentiation of oncogenicity by Lys63 mutation of c-HaRas appears primarily to be due to the loss of its sensitivity to the two major Ras signal attenuators (NF1 and GAP1).
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PMID:The role of Gln61 and Glu63 of Ras GTPases in their activation by NF1 and Ras GAP. 136 1

Members of the family of Ras-related guanosine triphosphate (GTP) binding proteins appear to take part in the regulation of a number of biological processes, including cell growth and differentiation. Three different classes of proteins that regulate the GTP binding and GTP hydrolytic activities of the Ras family members have been identified. These different regulatory proteins inhibit guanosine diphosphate (GDP) dissociation (designated as GDIs), stimulate GDP dissociation and GDP-GTP exchange (designated as GDSs), or stimulate GTP hydrolysis (designated as GAPs). In the case of the Ras-like protein CDC42Hs, which is the human homolog of a Saccharomyces cerevisiae cell division cycle protein, the GDI protein also inhibited both the intrinsic and GAP-stimulated hydrolysis of GTP. These findings establish an additional role for the GDI protein--namely, as a guanosine triphosphatase (GTPase) inhibitory protein for a Ras-like GTP binding protein.
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PMID:A GDP dissociation inhibitor that serves as a GTPase inhibitor for the Ras-like protein CDC42Hs. 143 91

Serum and growth factors can increase the proportion of Ras in the active guanosine triphosphate (GTP)-bound form. Growth factors might stimulate guanine nucleotide exchange or decrease the activity of the guanosine triphosphatase-activating proteins GAP and neurofibromin (NF1). In NIH 3T3 cells that overexpress the mutant Ras protein His116, which releases bound guanine nucleotide at a constitutively high rate and retains sensitivity to GAP and NF1, the proportion of GTP bound to the His116 protein was not altered by serum or platelet-derived growth factor. However, these mitogens increased the proportion of Ras in the GTP-bound form in cells that overexpressed control Ras proteins with a normal intrinsic rate of guanine nucleotide release. The amount of GTP-bound His116 or control Ras proteins was higher in cells at low density than in cells at high density, which have more GAP-like activity. The lower proportion of GTP-bound Ras in NIH 3T3 cells at high density may result from increased GAP-like activity. By contrast, serum and platelet-derived growth factors appear to stimulate guanine nucleotide exchange.
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PMID:Mechanistic aspects of signaling through Ras in NIH 3T3 cells. 149 80

Guanosine triphosphatase (GTPase) activity of Ras is increased by interaction with Ras-GAP (GTPase-activating protein) or with the GAP-related domain of the type 1 neurofibromatosis protein (NF1-GRD), but Ras is not affected by interaction with cytoplasmic and membrane forms of Rap-GAP; Rap1A, whose effector function can suppress transformation by Ras, is sensitive to both forms of Rap-GAP and resistant to Ras-GAP and NF1-GRD. A series of chimeric proteins composed of portions of Ras and Rap were constructed; some were sensitive to Ras-GAP but resistant to NF1-GRD, and others were sensitive to cytoplasmic Rap-GAP but resistant to membrane Rap-GAP. Sensitivity of chimeras to Ras-GAP and cytoplasmic Rap-GAP was mediated by amino acids that are carboxyl-terminal to the effector region. Residues 61 to 65 of Ras conferred Ras-GAP sensitivity, but a larger number of Rap1A residues were required for sensitivity to cytoplasmic Rap-GAP. Chimeras carrying the Ras effector region that were sensitive only to Ras-GAP or only to cytoplasmic Rap-GAP transformed NIH 3T3 cells poorly. Thus, distinct amino acids of Ras and Rap1A mediate sensitivity to each of the proteins with GAP activity, and transforming potential of Ras and sensitivity of Ras to Ras-GAP are at least partially independent properties.
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PMID:Heterogeneous amino acids in Ras and Rap1A specifying sensitivity to GAP proteins. 174 34

Ras-GAP (GTPase activating protein) is a regulatory protein that stimulates the intrinsic guanosine triphosphatase (GTPase) activity of the proto-oncogene product p21ras. A domain of the neurofibromatosis gene product (NF1) that has sequence similarity to the catalytic domain of Ras-GAP and to yeast IRA gene products also has a specific stimulatory activity toward p21ras GTPase. Arachidonic acid and phosphatidic acid inactivate GAP, but no agents have been identified that stimulate GAP and thereby switch p21ras off. With the use of recombinant Ha-c-Ras and Ras-GAP, NF1, and GAP catalytic domains, it was found that prostaglandins PGF2 alpha and PGA2 stimulated Ras-GAP and that prostacyclin PGI2 inhibited Ras-GAP. The stimulatory effect of PGF2 alpha was saturable and structure-specific and competed with the inhibitory effect of arachidonic acid. Arachidonic acid also inhibited the catalytic activity of NF1, but prostaglandins were not stimulatory. These results suggest a mechanism for the allosteric control of Ras function through the modulation of arachidonate metabolism.
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PMID:Regulation of Ras-GAP and the neurofibromatosis-1 gene product by eicosanoids. 190 23

The ras proto-oncogene products appear to relay intracellular signals via the Ras guanosine triphosphatase (GTPase) activator protein, GAP. In dog epithelial cells expressing human platelet-derived growth factor (PDGF) receptors, binding of PDGF caused approximately one-tenth of the total GAP molecules to complex with the receptor. Studies with mutant PDGF receptors showed that maximum association required both receptor kinase activity and phosphorylatable tyrosine residues at both the identified sites of receptor autophosphorylation.
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PMID:Binding of GAP to activated PDGF receptors. 215 84

Krev-1 is known to suppress transformation by ras. However, the mechanism of the suppression is unclear. The protein product of Krev-1, Rap1A-p21, is identical to Ras-p21 proteins in the region where interaction with guanosine triphosphatase (GTPase) activating protein (GAP) is believed to occur. Therefore, the ability of GAP to interact with Rap1A-p21 was tested. Rap1A-p21 was not activated by GAP but bound tightly to GAP and was an effective competitive inhibitor of GAP-mediated Ras-GTPase activity. Binding of GAP to Rap1A-p21 was strictly guanosine triphosphate (GTP)-dependent. The ability of Rap1A-p21 to bind tightly to GAP may account for Krev-1 suppression of transformation by ras. This may occur by preventing interaction of GAP with Ras-p21 or with other cellular proteins necessary for GAP-mediated Ras GTPase activity.
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PMID:Inhibition of GTPase activating protein stimulation of Ras-p21 GTPase by the Krev-1 gene product. 216 10


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