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)

Nitric oxide (NO) has been embroiled in the regulation of insulin secretion from the pancreatic beta cells and hence for the pathophysiology of diabetes mellitus. The present study was undertaken to assess the effects of hydroxylamine, a nitric oxide donor, on Ca(2+) handling in individual mouse pancreatic beta cells. Cytoplasmic Ca(2+) concentration ([Ca(2+)]i) was measured using dual wavelength microfluorometry and the indicator fura 2. In the presence of 3 mM glucose hydroxylamine raised [Ca(2+)]i in 90% of cells and the response was insensitive to methoxyverapamil and also to the intracellular Ca(2+) ATPase inhibitor, thapsigargin. At 11 mM glucose, the [Ca(2+)]i oscillations were abolished by hydroxylamine in a dose dependent manner. The addition of high concentrations of hydroxylamine (100 microM and 1 mM) resulted in a rapid disappearance of the oscillations with suppression of [Ca(2+)]i to near baseline level in a reversible manner. However, 90% of the beta-cells preserved the oscillatory [Ca(2+)]i activity in the presence of 10 microM hydroxylamine. At sustained elevated [Ca(2+)]i, obtained by depolarization with non metabolizable agonist, tolbutamide (1 mM), there was no effect of hydroxylamine; moreover, the inhibitory effects of hydroxylamine was counteracted by tolbutamide, suggesting that the effects of hydroxylamine is mediated by inhibition of metabolism leading to opening of K(+)(ATP) channel and decrease in Ca(2+) influx. When [Ca(2+)]i was maintained at sustained elevated state by at 11 mM glucose in the presence of glucagon, hydroxylamine at lower concentrations (<or=100 microM) induced generation of oscillatory [Ca(2+)]i signals. The generation of [Ca(2+)]i transients in the presence of glucagon was also abolished by hydroxylamine. The inhibitory effect of 1 mM hydroxylamine couldn't be transposed to oscillation by methylene blue, an inhibitor of guanylate cyclase and formation of c GMP. Thus the restraining effect of NO donor is probably not mediated by activation of c GMP signaling pathway rather reflects more direct effect of NO. It is concluded that, NO plays a dual role-at high concentrations it inhibits oscillatory [Ca(2+)]i signals in glucose-stimulated pancreatic beta-cells whereas it can regenerate the oscillatory activity at certain low concentrations when [Ca(2+)]i response is non oscillatory.
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PMID:Modulation of glucose induced oscillatory [Ca2+]i signals by nitric oxide in ob/ob mouse pancreatic beta-cells. 1937 36

The distinct biological properties of nitroxyl (HNO) have focused research regarding the chemistry and biology of this redox relative of nitric oxide (NO). Much of HNO's biological activity appears to arise through modification of thiol-containing enzymes and proteins and reactions with iron-heme proteins. The reactions of HNO with hemoglobin and myoglobin serve as a general model for understanding HNO reactivity with other heme proteins. Interaction of HNO with catalase and soluble guanylate cyclase may have biological roles. While endogenous HNO formation remains to be described, we summarize work that reveals HNO formation through oxidative heme protein metabolism of various nitrogen-containing substrates including hydroxylamine, hydroxyurea, hydroxamic acids, cyanamide, and sodium azide. Depending on the enzyme, the nascent HNO reductively nitrosylates the heme protein or escapes the heme pocket as HNO. Such results define an alternative metabolism-based route to HNO that may inform endogenous HNO production.
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PMID:Oxidative heme protein-mediated nitroxyl (HNO) generation. 2050 24


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