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)

Atrial natriuretic factor (ANF) is a peptide hormone from the heart atrium with potent natriuretic and vasorelaxant activities. The natriuretic activity of ANF is, in part, mediated through the adrenal gland, where binding of ANF to the 130-kDa ANF receptor causes suppression of aldosterone secretion. Incubation of bovine adrenal membranes at pH < 5.6 caused a rapid and spontaneous cleavage of the 130-kDa ANF receptor, yielding a 65-kDa polypeptide that could be detected by photoaffinity labeling by 125I-labeled N alpha 4-azidobenzoyl-ANF(4-28) followed by SDS/PAGE under reducing conditions. Within 20 min of incubation at pH 4.0, essentially all the 130-kDa receptor was converted to a 65-kDa ANF binding protein. This cleavage reaction was completely inhibited by inclusion of 5 mM EDTA. When SDS/PAGE was carried out under non-reducing conditions, the apparent size of the ANF receptor remained unchanged at 130 kDa, indicating that the 65-kDa ANF-binding fragment was still linked to the remaining part(s) of the receptor polypeptide through a disulfide bond(s). The disappearance of the 130-kDa receptor was accompanied by a parallel decrease in guanylate cyclase activity in the membranes. Inclusion of EDTA in the incubation not only prevented cleavage of the 130-kDa receptor, but also protected guanylate cyclase activity, indicating that proteolysis, but not the physical effects of the acidic pH, causes inactivation of guanylate cyclase. The 130-kDa ANF receptor in adrenal membranes was competitively protected from photoaffinity labeling by ANF(1-28) or ANF(4-28), but not by atriopeptin I [ANF(5-25)] or C-ANF [des-(18-22)-ANF(4-23)-NH2]. On the contrary, the 65-kDa ANF-binding fragment generated after incubation at pH 4.0 was protected from labeling by any of the above peptides, indicating broader binding specificity. After incubation in the presence of EDTA, the 130-kDa ANF receptor, which was protected from proteolysis, retained binding specificity identical to that of the 130-kDa receptor in untreated membranes. The results indicate that the broadening of selectivity is caused by cleavage, but not by the physical effect of acidic pH. Spontaneous proteolysis of ANF receptor by an endogenous metalloendopeptidase, occurring with concomitant inactivation of guanylate cyclase activity and broadening of ligand-binding selectivity, may be responsible for the generation of low-molecular-mass receptors found in the adrenal gland and other target organs of ANF. The proteolytic process may play a role in desensitization or down-regulation of the ANF receptor.
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PMID:Proteolytic cleavage of atrial natriuretic factor receptor in bovine adrenal membranes by endogenous metalloendopeptidase. Effects on guanylate cyclase activity and ligand-binding specificity. 135 9

Incubation of the adrenal membranes at pH 3.5-5.6 resulted in apparent proteolysis of 140 kDa protein to yield a 70 kDa polypeptide containing an ANF-binding site, which could be photoaffinity labeled by [125I]4-azidobenzoyl monoiodo ANF-(4-28). This 70 kDa fragment was found to be disulfide-linked to the remaining segment(s) of the molecule, giving a total apparent Mr of 140,000 when not reduced. The acidic pH-dependent proteolysis was rapid even at 0 degree C, suggesting close association of an endopeptidase with ANF receptor. The proteolysis was inhibited by EDTA, but not by phenylmethanesulfonyl fluoride, N-ethylmaleimide or pepstatin, indicating that the enzyme is a metalloendopeptidase. The inhibition was reversed by ZnCl2 or MnCl2, but not CaCl2 or MgCl2. The adrenal membranes contained guanylate cyclase activity of 1.1 nmol/min/mg protein using Mn-GTP as a substrate, which could be stimulated by 0.1 microM ANF to 2.7 nmol/min/mg. The membranes showed high affinity to ANF-(1-28) and ANF-(4-28), but little affinity to the truncated peptides ANF-(5-25) and ANF-(7-23). After treatment at pH 3.5 and 0 degrees C for 15 min, the membranes retained ANF-binding activity but with broader specificity, exhibiting high affinity to all four peptides above. It was suggested that an acidic metalloendopeptidase in the adrenal membranes may be involved in ANF receptor cleavage.
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PMID:Acidic pH- and metal ion (Zn++ or Mn++)-dependent proteolysis of 140 kDa atrial natriuretic factor receptor in bovine adrenal cortex plasma membranes: evidence for membrane-bound acidic metalloendopeptidase. 289 2

The inactivation of rat atrial natriuretic factor (ANF) was studied using a bioassay, ANF-stimulated guanylate cyclase activity. Rat kidney membranes degraded ANF into biologically inactive forms. The primary cleavage site appears to be the Cys105-Phe106 bond. The degradation, measured by HPLC, followed classical Michaelis-Menten kinetics. The sensitivity of the enzyme to inhibitors suggested it to be a metalloendopeptidase, resembling neutral endopeptidase 24.11. When this enzyme, characterised by its enkephalin-degrading activity, was compared to the enzyme responsible for ANF inactivation, striking differences were found in tissue distribution, pH-dependence and sensitivity to protein-modifying reagents. It is concluded that an enzyme similar to endopeptidase 24.11 may be responsible for inactivation of atrial peptides in the rat.
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PMID:Degradation of atrial natriuretic peptides by an enzyme in rat kidney resembling neutral endopeptidase 24.11. 297 21