Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.6.1.2 (guanylate cyclase)
 8,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Guanylate cyclase activity (GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2.), measured in purified rat liver plasma membranes, was markedly increased by treatment with various purified proteases. The effect was maximal with trypsin, alpha-chymotrypsin, papain, and thermolysin (6- to 8-fold increase with 5 to 20 microgram of protease/ml) and lower with subtilisin and elastase (3- to 4-fold increase). The activation was due to an increase in the maximal velocity of the cyclizing reaction. No modification was observed either in the apparent affinity for the substrate MnGTP or in the cooperative behavior of the enzyme kinetics which displayed Hill coefficients of 1.6 for both basal and activated states. The Triton X-100-dispersed guanylate cyclase remained sensitive to papain, which suggests that the action of proteases was not restricted to an indirect action upon the membranous environment of the guanylate cyclase. In contrast, the cytosolic soluble guanylate cyclase, assayed in the presence or absence of sodium azide, was absolutely insensitive to papain. Thus, proteolysis represents a previously undescribed mechanism for activating membranous guanylate cyclase systems, which might be of importance in the physiological regulation of this enzyme.
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PMID:Activation of rat liver guanylate cyclase by proteolysis. 3 29

The soluble form of guanylate cyclase (EC 4.6.1.2) from rat lung has been purified to homogeneity by a one-step immunoaffinity chromatographic procedure. The purified soluble guanylate cyclase has specific activities of 432 and 49.1 nmol of cyclic GMP formed per min/mg protein with manganese and magnesium ions as a cofactor, respectively. This represents a purification of approximately 2,000-fold with a 50% recovery. The native enzyme has a molecular weight of 150,000 and a Stokes radius of 4.8 nm as determined on Spherogel TSK-G3000SW gel permeation chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis results in two protein-staining bands with molecular weights of 82,000 and 70,000. The purified soluble guanylate cyclase was also subjected to native polyacrylamide gel electrophoresis, isoelectric focusing electrophoresis, ion exchange chromatography, and GTP-agarose affinity chromatography. These additional purification procedures confirmed the presence of a single protein peak coincident with enzyme activity. The two subunits separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis were shown to have different primary structures by immunoblotting with monoclonal and polyclonal antibodies prepared against purified soluble guanylate cyclase and by peptide mapping with papain or Staphylococcus aureus V8 protease treatment. These data demonstrate that soluble guanylate cyclase purified from rat lung is a heterodimer composed of 82,000- and 70,000-dalton subunits with different primary structures.
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PMID:Soluble guanylate cyclase from rat lung exists as a heterodimer. 287 14

The natriuretic peptide receptor-C (NPR-C) constitutes greater than 95% of the natriuretic peptide binding sites in vivo. This cell surface glycoprotein is a disulfide-linked homodimer with a subunit molecular weight of 68,000. Two sources and types of ANP affinity-purified human NPR-C were used to map disulfide linkages and glycosylation sites of this receptor by mass spectrometry: the extracellular domain obtained by papain cleavage of a receptor-IgG fusion protein expressed in Chinese hamster ovary cells, and a baculovirus/Sf9-expressed cytoplasmic truncation mutant in which 34 of 37 cytoplasmic domain amino acids were deleted. Two intramolecular disulfide bonded loops were found in the 435 amino acid extracellular domain (C63-C91, C168-C216). The juxtamembrane residues C428 and C431 are involved in homodimer formation, confirmed by site-directed mutagenesis of full-length NPR. Three of the four potential Asn-linked glycosylation sites are occupied: N41 (complex), N248 (high mannose), and N349 (complex; partial occupancy). These data describe the intra- and intermolecular linkages in NPR-C, providing a model for the homologous guanylyl cyclase receptors, NPR-A and NPR-B; both of the cyclase receptors likely contain the first amino-terminal 29 amino acid loop, but only NPR-A possesses the second 49 amino acid loop in common with NPR-C.
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PMID:The disulfide linkages and glycosylation sites of the human natriuretic peptide receptor-C homodimer. 772 88

Using a variety of fold-recognition methods, a novel eukaryotic cysteine proteinase (ECEPE) family has been identified. This family encompasses sequences from an uncharacterized KOG4621, including the Arabidopsis thaliana guanylyl cyclase-related protein AtGC1. ECEPE proteins are predicted to possess the papain-like cysteine proteinase fold and are evolutionarily linked to C39 peptidases. The presence of the invariant Cys-His-Asp/Asn catalytic triad and the oxyanion-hole glutamine residue characteristic of papain-like cysteine proteases indicate that ECEPE proteins might function as proteases.
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PMID:ECEPE proteins: a novel family of eukaryotic cysteine proteinases. 1545 Jun 6

The aim of the present study was to investigate the effects of quercetin on colon contractility and voltage-dependent Ca(2+) channels in the single smooth muscle cell isolated from the proximal colon of guinea-pig and to clarify whether its effect on L-type Ca(2+) current (I(Ca,L)) would be related to its myorelaxing properties. Colon smooth muscle strips were used to take contractile tension recordings. Smooth muscle cells were freshly isolated from the proximal colon of guinea-pig by means of papain treatment. I(Ba,L) (barium instead of calcium as current carrier) was measured by using whole-cell patch-clamp techniques. The results showed that quercetin relaxed colon muscle strips in a concentration-dependent manner and antagonized the contractile effect of acetylcholine and neostigmine. Preincubation with indomethcin [cyclooxygenase (COX) inhibitor] and methylene blue [guanylate cyclase (GC) inhibitor] significantly attenuated the relaxing effect of quercetin, respectively. Quercetin increased I(Ba,L) in a concentration- [EC(50)= (7.59+/-0.38) mumol/L] and voltage-dependent pattern, and shifted the maximum of the current-voltage curve by 10 mV in the depolarizing direction without modifying the threshold potential for Ca(2+) influx. Quercetin shifted the steady-state inactivation curve toward more positive potentials by approximately 3.75 mV without affecting the slope of activation and inactivation curve. H-89 (PKA inhibitor) abolished quercetin-induced I(Ba,L) increase, while cAMP enhanced the quercetin-induced I(Ba,L) increase. The patch-clamp results proved that quercetin increased I(Ba,L) via PKA pathway. It is therefore suggested that the relaxing effect of quercetin attributes to the interaction of GC and COX stimulation, as well as the antagonism effect on acetylcholine, which hierarchically prevails over the increase in the Ca(2+) influx to be expected from I(Ca,L) stimulation.
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PMID:Effect of quercetin on colon contractility and L-type Ca(2+) channels in colon smooth muscle of guinea-pig. 2002 91