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)

We have characterized protein phosphorylation in vitro in subcellular fractions from Drosophila melanogaster heads. Optimal conditions for the incorporation of 32P into proteins, and its dependence on ATP, divalent cations, and cyclic nucleotides have been determined, as well as the effect of inhibitors of ATPase, protein phosphatase, and protein kinase on protein phosphorylation. Among these inhibitors, Zn2+ was found to affect the incorporation of 32P into specific bands and p-hydroxymercuribenzoate was found to be most suited for freezing the activity of both kinases and phosphatases. Cyclic AMP-dependent protein kinase (cAMP-dPK) activity was present in both supernatant (S2) and particulate (P2) fractions, with the majority (60-85%, depending on the homogenization medium) being associated with S2, as determined by phosphorylation of exogenous synapsin I. cAMP-dPK catalyzed the phosphorylation of at least 18 endogenous polypeptides in S2 and at least 10 endogenous polypeptides in P2. These proteins could be classified on the basis of the extent of stimulation of phosphorylation by cyclic nucleotides, dependence on cyclic nucleotide concentration, and rate of phosphorylation. A phosphoprotein of 51 kilodaltons (pp51) was a major component of the S2 and P2 fractions and displayed properties expected from the regulatory subunit of the cAMP-dPK, R-II. A phosphoprotein doublet of approximately 37 kilodaltons (pp37) was stimulated to the largest extent by cAMP in the P2 and S2 fractions. The phosphorylation of several proteins in both fractions was significantly lowered by the mammalian Walsh inhibitor of cAMP-dPK, whereas in some cases the stimulation of phosphorylation of the same proteins by exogeneous cAMP was relatively small. Phosphoproteins from two learning mutants known to be deficient in cAMP metabolism, dnc and rut, were analyzed for their extent of phosphorylation in the presence of a stable cAMP analogue; no significant differences from normal were detected, suggesting that the genetic defect in cAMP metabolism is not accompanied by constituent abnormalities in phosphorylated substrates in the adult fly, and that the physiological defects in these mutants result from aberrations in the interaction of the cAMP cascade with normal substrates. The majority of Ca2+/calmodulin kinase activity (80-90%, depending on the homogenization procedure) was associated with S2, as revealed by phosphorylation of exogenous synapsin I. Two endogenous substrates for this kinase in P2 had molecular masses of approximately 45 and 87 kilodaltons. At least 11 substrates for the Ca2+/calmodulin-dependent kinase were detected in S2.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:In vitro protein phosphorylation in head preparations from normal and mutant Drosophila melanogaster. 304 Sep 7

Enhancement of endogenous kinase-dependent in vitro protein phosphorylation of subcellular fractions from brains and spinal cords of hens paralyzed 3 weeks after intoxication with tri-o-cresyl phosphate was correlated with the development of organophosphorus compound-induced delayed neurotoxicity (OPIDN). This was documented by showing: parallel dose-dependence curves for both responses, phosphorylation enhancement in proteins from hens treated with OPIDN-producing O-4-bromo-2,5-dichlorophenyl-O-methyl phenylphosphonothioates, but not in those treated with non-OPIDN-producing O,O-diethyl-O-4-nitrophenyl phosphorothioate or tri-p-cresyl phosphate, and shared age and species selectivities for both effects. These results strengthen our earlier observation of a close temporal relationship between protein phosphorylation enhancement and OPIDN. Further studies suggest that the proximate cause of the enhanced phosphorylation is not related to an alteration in protein phosphatase activity or to the preservation of a rate-limiting pool of [gamma-32P]ATP by adenosine triphosphatase inhibition. Therefore, it is most likely related either to altered protein kinase activity or amount (due to chemically originated physical disruption of the neuron). These data support the hypothesis that increased protein phosphorylation may be involved in the development of OPIDN.
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PMID:Relationship of tri-O-cresyl phosphate-induced delayed neurotoxicity to enhancement of in vitro phosphorylation of hen brain and spinal cord proteins. 377 11

1. The action of beryllium on the following enzymes has been examined: alkaline phosphatase (Escherichia coli and kidney), acid phosphatase, phosphoprotein phosphatase, apyrase (potato), adenosine triphosphatase (liver nuclei, liver mitochondria, brain microsomes), glucose 6-phosphatase, polysaccharide phosphorylases a and b, phosphoglucomutase, hexokinase, phosphoglyceromutase, ribonuclease, A-esterase (rabbit serum), cholinesterase (horse serum), chymotrypsin. Alkaline phosphatase and phosphoglucomutase are inhibited by 1mum-beryllium sulphate whereas the other enzymes are largely unaffected by 1mm-beryllium sulphate. 2. Possible mechanisms for the inhibition of phosphoglucomutase and alkaline phosphatase are discussed.
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PMID:The inhibition of enzymes by beryllium. 428 87

In intact red cells a CaMg-ATPase activity commensurable with that of the Ca-pump exists consisting mainly of protein kinase-protein phosphatase enzymes. The Ca:ATP stoichiometry of the Ca-pump is most probably 2:1, the deviation from this value at low [Ca] in inside-out-vesicles is possibly an artifact. Ca-affinity of the Ca-pump is low in intact red cells, where both calmodulin and calmodulin binding protein are present, and the cAMP-dependent activatory mechanism found in many other cells is inactive. Ca-affinity, however, can be enhanced by A23187, by Ca-EGTA buffers at the internal membrane surface (eliminating some structural divalent cations?), by enrichment in calmodulin and loss in calmodulin binding protein and by mild proteolytic effects on the inner surface of the membrane. Mild trypsin treatment of the external surface of the membrane increases the hydrolysis rate, but not the Ca-affinity of the Ca-pump and other CaMg-ATPases, increases membrane protein phosphorylation and protects against echinocytic shape transformation. All these findings reflect the interrelatedness of several membrane components influencing the rate and/or Ca-affinity of CaMg-ATPases.
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PMID:Ca-transport and CaMg-ATPase activity in human red cell preparations. 611 87

Membrane protein phosphorylation has been studied in intact human erythrocytes and in resealed erythrocyte ghosts by measuring the incorporation of 32P into band 2 of spectrin. alpha-Adrenergic agonists and Ca+2 stimulate 32P-phosphate incorporation, an effect inhibited by trifluoperazine and diminished in resealed ghosts depleted of calmodulin. Ghosts prepared with endogenous calmodulin or resealed around purified calmodulin exhibit norepinephrine- and Ca+2-stimulated phosphorylation only in the presence of [gamma-32P]-ATP. Ghosts resealed with or without calmodulin in the presence of unlabelled ATP show no net gain or loss of 32P in membrane proteins when exposed to norepinephrine or calcium stimulation. These observations suggest that calcium and norepinephrine stimulation of membrane protein phosphorylation is mediated by calmodulin-dependent spectrin kinase activity, rather than by increased turnover by spectrin ATPase or by inhibition of phosphospectrin phosphatase.
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PMID:Calmodulin-dependent spectrin kinase activity in human erythrocytes. 612 May 20

Purified rabbit skeletal muscle myosin is phosphorylated on one type of light-chain subunit (P-light chain) by calmodulin-dependent myosin light chain kinase and dephosphorylated by phosphoprotein phosphatase C. Analyses of the time courses of both phosphorylation and dephosphorylation of skeletal muscle myosin indicated that both reactions, involving at least 90% of the P-light chain, were kinetically homogeneous. These results suggest that phosphorylation and dephosphorylation of rabbit skeletal muscle myosin heads are simple random processes in contrast to the sequential phosphorylation mechanism proposed for myosin from gizzard smooth muscle. We also examined the effect of phosphorylation of rabbit skeletal muscle myosin on the actin-activated ATPase activity. We observed an apparent 2-fold decrease in the Km for actin, from about 6 microM to about 2.5 microM, with no significant effect on the Vmax (1.8s-1) in response to P-light-chain phosphorylation. There was no significant effect of phosphorylation on the ATPase activity of myosin alone (0.045 s-1). ATPase activation could be fully reversed by addition of phosphatase catalytic subunit. The relationship between the extents of P-light-chain phosphorylation and ATPase activation (at 3.5 microM actin and 0.6 microM myosin) was essentially linear. Thus, in contrast to results obtained with myosin from gizzard smooth muscle, these results suggest that cooperative interactions between the myosin heads do not play an important role in the activation process in skeletal muscle. Since the effect of P-light-chain phosphorylation is upon the Km for actin, it would appear to be associated with a significant activation of ATPase activity only at appropriate concentrations of actin and salt.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Phosphorylation kinetics of skeletal muscle myosin and the effect of phosphorylation on actomyosin adenosinetriphosphatase activity. 623 85

Enzyme cytochemical and immunocytochemical techniques at the light and electron microscope levels were used to study the distribution of potential markers of chemical transformation in rodent bladders. In rat tumours induced by in vivo treatment with methylnitrosourea, alkaline phosphatase localization was normal on the external surface of the plasma membranes of some cells but abnormal in others where reaction product was seen only on intracellular membranes. 5'-Nucleotidase localization was abnormal in all cells, being seen on endoplasmic reticulum and nuclear membranes only, while in normal bladders only ectoenzyme localization was seen. Heterogeneity of alkaline phosphatase amd 5'-nucleotidase localization was seen on the plasma membranes of these tumours after 15 days in organ culture. Some cells produced enzyme and others did not; in other cells only parts of the membrane reacted heavily, while other regions were negative. In transformed cell cultures and tumours of mouse bladder derived by in vitro treatment of explants with dimethylbenz (a) anthracene, a bimodal pattern of alkaline phosphatase localization was seen. Cells had either normal ectoenzyme reaction product or abnormal intracellular membrane reaction product. 5'-Nucleotidase and ADPase were lost after transformation while cAMP-phosphodiesterase was retained as an ectoenzyme. Mg.ATPase and a cAMP-independent, calcium-insensitive 'protein phosphatase' were induced in transformed cell cultures. An epithelial antigen was detected in the cytoplasm of both normal and transformed cells associated with reticular cytoplasmic ground substance, plasma membrane vesicles and cytoskeletal elements.
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PMID:Cytochemical markers of bladder carcinogenesis. 627 42

The actin-activated ATPase activity of myosin II from Acanthamoeba castellanii is inhibited by phosphorylation of 3 serine residues near the carboxyl end of the heavy chain of the molecule. We have purified a protein phosphatase from Acanthamoeba using myosin II as a substrate. This phosphatase has a molecular weight of 39,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and an isoelectric point in urea of 5.2. The enzyme also is active against other phosphoserine protein substrates such as turkey gizzard smooth muscle myosin light chain, but not against a synthetic phosphotyrosine protein substrate. It does not hydrolyze ATP or p-nitrophenol phosphate. No effector has been found to increase substantially the activity of the enzyme as isolated, but it is inhibited by ATP, pyrophosphate, and NaF. This inhibition is reduced in the presence of MnCl2. The Mg2+-dependent actin-activated ATPase of myosin II is activated by dephosphorylation of phosphorylated myosin II by the phosphatase. Its broad substrate specificity, molecular weight, and response to protein phosphatase inhibitors suggest that the Acanthamoeba protein phosphatase is a type 2A phosphatase (Cohen, P. (1982) Nature (Lond.) 206, 613-620).
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PMID:Purification of a protein phosphatase from Acanthamoeba that dephosphorylates and activates myosin II. 631 29

Cytosol prepared from rat preovulatory ovarian follicles contained several specific substrates which were phosphorylated by [gamma 32P] ATP in the presence of 2 microM cyclic AMP (cAMP) or 780 nM of highly purified catalytic subunit. These substrates were identified as RII, the regulatory subunit of type II cAMP-dependent protein kinase, an Mr = 43,000 protein presumed to be actin, and four other proteins with Mr = 36,500-15,000. A marked decrease in phosphorylation of these proteins was observed within 6-48 h of human chorionic gonadotropin (hCG)-induced ovulation and luteinization in hormonally primed immature rats. The phosphorylation of these proteins was also low in cytosol of corpora lutea isolated on Days 2, 4, 9, 13 and 23 of pregnancy. The decrease in phosphorylation of RII was associated primarily with a decrease in substrate content as measured by photoaffinity labeling and silver staining techniques, and not to a marked increase in phosphoprotein phosphatase and adenosinetriphosphatase (ATPase) activities. Whereas the decreased phosphorylation of other proteins is also presumed to be related to a decrease in their cytosol content, the data do not exclude the possibility that luteal tissue contains a specific phosphoprotein phosphatase which is not present in granulosa or theca cells of preovulatory follicles. We conclude that luteinizing hormone (LH) or hCG, and thereby cAMP itself, induces the rapid loss of specific phosphoproteins which may be involved in regulating cAMP action in granulosa cells.
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PMID:Changes in content and phosphorylation of cytosol proteins in luteinizing ovarian follicles and corpora lutea. 632 74

The activities of nuclear envelope-associated protein phosphokinase and protein phosphatase were determined in nuclear ghosts from liver and oviduct of quails. The protein kinase was found to be inhibited by poly(A) by 75%. During the kinase reaction proteins with molecular weights of 106 000 and 64 000 were phosphorylated. The phosphoprotein phosphatase from liver was stimulated to 190% by poly(A), whereas only a slight enhancing effect by this polymer was determined with the oviduct enzyme (to 125%). Comparative determinations of the nuclear ghost-associated enzyme activities revealed the following values (in nmol Pi/min per 10(8) ghosts); oviduct: phosphokinase, 0.015; phosphatase, 0.004 and nucleoside triphosphatase, 39.4; and liver: phosphokinase, 0.044; phosphatase, 0.012 and nucleoside triphosphatase, 11.7. These data indicate that phosphorylation/dephosphorylation proceeds independently of the nucleoside triphosphatase cycle. This assumption is supported by analytical results revealing that no marked dephosphorylation occurs after poly(A) binding to the nuclear envelope. Moreover, stoichiometrical data showed a nearly 1:1 molar ratio between ATP-binding and phosphorylation of nuclear envelope protein. From these findings a new model for the nucleoside triphosphatase-mediated poly(A)(+)mRNA efflux from nuclei is deducted, proposing phosphokinase and phosphatase only to modulate the affinity of the 'carrier structure' for poly(A) (+)mRNA, but not to constitute the nucleoside triphosphatase.
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PMID:The role of protein phosphokinase and protein phosphatase during the nuclear envelope nucleoside triphosphatase reaction. 632 88


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