Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.99.1 (NADPH-diaphorase)
 3,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A rapid enzymatic method was developed for the assay of serum argininosuccinate lyase (ASAL: EC 4.3.2.1) which is a useful marker enzyme for diagnosis of parenchymal liver diseases. Fumarate, liberated from argininosuccinate in the lyase-mediated reaction, was converted to pyruvate via L-malate by the actions of fumarase and malic enzyme in the presence of NADP+. The NADPH formed was then oxidized with a diaphorase-resazurin system to give a highly fluorescent resorufin. All the enzymatic reactions proceeded continuously in 0.1 M Tris-HCl buffer (pH 7.5) and allowed direct assay of ASAL in serum by monitoring the increase in the fluorescence intensity due to resorufin. The method is rapid and sensitive; only 50 microliter of serum is required. This method was used to detect increases in the activities in sera from patients with liver diseases.
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PMID:An enzymatic method for the assay of serum argininosuccinate lyase. 367 95

Neurons that synthesize nitric oxide from arginine produce stoichiometric amounts of citrulline. We investigated whether nitric oxide-releasing enteric neurons have the capacity to recycle citrulline to arginine and thereby sustain nitrergic neurotransmission. Argininosuccinate synthetase-like immunoreactivity and argininosuccinate lyase-like immunoreactivity, enzymes capable of citrulline to arginine conversion, were both localized in discrete populations of myenteric and submucosal neurons in the canine proximal colon. Argininosuccinate synthetase-like immunoreactivity and argininosuccinate lyase-like immunoreactivity co-localized with neuronal beta-nicotinamide adenine dinucleotide phosphate diaphorase staining, a marker for nitric oxide synthase. The functional significance of argininosuccinate synthetase-like immunoreactivity and argininosuccinate lyase-like immunoreactivity was shown by testing the effects of exogenous citrulline on responses to enteric inhibitory nerve stimulation, which were assessed by measuring contractions, inhibitory junction potentials and electrical slow waves. As shown previously, arginine analogues (L-nitroarginine methyl ester or L-nitroarginine; 100 microM) inhibited nitric oxide-dependent responses, and excess L-arginine restored inhibitory responses. Citrulline alone (0.1-2 mM) had no effect on nitrergic transmission under control conditions, but in the presence of L-nitroarginine methyl ester or L-nitroarginine, citrulline (0.1-2 mM) restored nitrergic transmission in a concentration-dependent manner. Other neutral amino acids (L-serine, L-leucine) did not mimic the effects of citrulline. Taken together, these data suggest that enteric nitrergic neurons have the enzymatic apparatus and functional capability of recycling citrulline to arginine.
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PMID:Recycling of L-citrulline to sustain nitric oxide-dependent enteric neurotransmission. 854 1

Results from biochemical and pharmacologic studies suggest that Lcitrulline is taken up by cerebral perivascular nerves and is converted to Larginine for synthesizing nitric oxide (NO). The current study was designed using morphologic techniques to determine whether Lcitrulline is taken up into axoplasm of perivascular nerves and to explore the possibility that conversion of Lcitrulline to Larginine in these nerves is through the argininosuccinate pathway in porcine cerebral arteries. Results from light and electron microscopic autoradiographic studies indicated that dense silver grains representing L-[3H] citrulline uptake were found in cytoplasm of perivascular nerves, smooth muscle cells, and endothelial cells. The neuronal silver grains were significantly decreased in arteries pretreated with glutamine, which has been shown biochemically to block neuronal uptake of Lcitrulline. Results from light and electron microscopic immunohistochemical and histochemical studies indicate that dense nitric oxide synthase-immunoreactive (NOS-I), argininosuccinate synthetase-immunoreactive (ASS-I), and argininosuccinate lyase-immunoreactive (ASL-I) fibers were found in the adventitia of cerebral arteries. NOS-, ASS-, and ASL-immunoreactivities fibers were found in the axoplasm and in the endothelium. In whole-mount preparations, the NOS-I, ASS-I, and ASL-I fibers were completely coincident with NADPH diaphorase fibers, suggesting that axoplasmic ASS, ASL, and NOS were co-localized in the same neurons. These studies provide the first morphologic evidence indicating that Lcitrulline is taken up into cytoplasm of cerebral perivascular nerves and that the axoplasmic enzymes catalyzing the conversion of Lcitrulline to Larginine (for synthesizing NO) by argininosuccinate pathway always are co-localized in same neurons. These results support the hypothesis that Lcitrulline, the by-product of NO synthesis, is recycled to form Larginine for synthesizing NO in perivascular nerves to mediate cerebral neurogenic vasodilation. Results of the current morphologic studies also support the presence of Lcitrulline-Larginine cycle in cerebral vascular endothelium.
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PMID:Morphologic evidence for L-citrulline conversion to L-arginine via the argininosuccinate pathway in porcine cerebral perivascular nerves. 929 May 86

Nitric oxide synthase (NOS), argininosuccinate synthetase (ASS), and argininosuccinate lyase (ASL) compose a cyclic pathway to form nitric oxide (NO). These enzymes, however, are localized differentially in most regions of the brain. To find out whether NOS, ASS, and ASL are colocalized in neurons of the spinal cord, we examined the distribution of these enzymes by using a double-labeling procedure combining fluorescent immunohistochemistry with an assay for reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d). Results indicate that neurons in the dorsal horn, the intermediolateral nucleus, and the central canal region were NADPH-d active (+) and NOS-, ASS-, and ASL-like immunoreactive (-LI). In laminae II and III of the dorsal horn, some NADPH-d (+) neurons were ASL-LI (8-30%) but only a few were ASS-LI (0.5-7%). In the nucleus intermediolateralis, a large portion of NADPH-d (+) neurons were ASL-LI (30-60%), whereas only a small portion of NADPH-d (+) neurons were ASS-LI (10-20%). In the central canal region, some NADPH-d (+) neurons were ASL-LI (15-40%), and a few NADPH-d (+) neurons were ASS-LI (3-16%). Thus, the results suggest that, in the nucleus intermediolateralis and the central canal region, NOS, ASS, and ASL are colocalized and form a cyclic pathway to produce NO, whereas, in the dorsal horn, these enzymes are more characteristically localized in different neurons, which may transport the substrates intercellularly.
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PMID:NADPH-diaphorase and cytosolic urea cycle enzymes in the rat spinal cord. 930 8

The presence of nitric oxide synthase (NOS), argininosuccinate synthetase (ASS), and argininosuccinate lyase (ASL) and their coexistence with NADPH-diaphorase (NADPHd), a marker for NOS, in the porcine sphenopalatine ganglia (SPG), pial veins, and the anterior cerebral arteries was examined using immunohistochemical and histochemical staining techniques. NOS-immunoreactive (I), ASS-I, and ASL-I fibers were found in pial veins and the anterior cerebral arteries. NOS, ASS, and ASL immunoreactivities were also found in neuronal cell bodies in the SPG. Almost all neuronal cell bodies in the SPG and nerve fibers in pial veins and the anterior cerebral arteries that were reactive to ASS, ASL, and NOS were also stained positively with NADPHd, suggesting that ASS, ASL, and NOS were colocalized in the same neurons in the SPG and perivascular nerves. With the use of in vitro tissue bath techniques, L-citrulline but not D-citrulline reversed inhibition of neurogenic vasodilation in isolated porcine pial veins produced by NOS inhibitors such as NG-nitro-L-arginine methyl ester. In the presence of L-aspartate, L-arginine was synthesized from L-citrulline in homogenates of SPG and endothelium-denuded cerebral arteries and pial veins. These results provide evidence indicating that perivascular nerves in pial veins like cerebral arteries can convert L-citrulline to L-arginine for synthesizing nitric oxide. The conversion is most likely via an argininosuccinate pathway.
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PMID:L-citrulline conversion to L-arginine in sphenopalatine ganglia and cerebral perivascular nerves in the pig. 937 53

The nitric oxide cycle consists of nitric oxide synthase, argininosuccinate synthetase and argininosuccinate lyase to form nitric oxide. We have examined the colocalization of nitric oxide synthase and the cytosolic urea cycle enzymes (argininosuccinate synthetase, argininosuccinate lyase and arginase) in the accessory olfactory bulb of the rat by using a double labeling procedure combining reduced-nicotinamide-adenine-dinucleotide-phosphate-diaphorase (NADPH-d) reaction with fluorescent immunocytochemistry. Each glomerulus showed a different NADPH-d activity, and those with the strongest NADPH-d activities were assembled in the caudomedial part of the accessory olfactory bulb. Argininosuccinate synthetase-like immunoreactive glomeruli were distributed in the caudomedial part of the accessory olfactory bulb, and most of them were also strongly NADPH-d positive. The mitral or tufted cells were argininosuccinate synthetase-, argininosuccinate lyase- and arginase-like immunoreactive, but were not NADPH-d positive. The granule cells were NADPH-d positive or argininosuccinate lyase-like immunoreactive, but were not argininosuccinate synthetase- or arginase-like immunoreactive. Some granule cells were both NADPH-d positive and argininosuccinate lyase-like immunoreactive. The results indicate the heterogeneity of glomeruli of the accessory olfactory bulb with respect to the distribution of these enzymes. The granule cells have nitric oxide synthase and argininosuccinate lyase, and thus may efficiently produce nitric oxide.
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PMID:NADPH-diaphorase and cytosolic urea cycle enzymes in the rat accessory olfactory bulb. 1058 62

Recycle of L-citrulline to form L-arginine in cerebral perivascular nerves has been well described, providing direct evidence that nitric oxide (NO) is synthesized and released from these nerves to act as the transmitter for vasodilation. NO is also synthesized and released from cerebral endothelial cells, involving L-citrulline conversion to L-arginine. Evidence for the presence of enzymes involved in the conversion, however, has not been shown. The presence of nitric oxide synthase (NOS), argininosuccinate synthetase (ASS), and argininosuccinate lyase (ASL), and their coexistence with NADPH-diaphorase (NADPHd), a marker for NOS, in endothelial cells of middle cerebral arteries and the circle of Willis of the pig, therefore, were examined using combined immunohistochemical and histochemical techniques. NOS-, ASS-, and ASL-immunoreactivities were found in almost all endothelial cells of all cerebral arteries examined. All ASS-, ASL-, and NOS-immunoreactive (I) endothelial cells also stained positively for NADPHd, suggesting that ASS, ASL, and NOS were colocalized in endothelial cells of middle cerebral arteries and the circle of Willis. These results provide morphological evidence that cerebral vascular endothelial cells like cerebral perivascular nerves contain enzymes necessary for recycling L-citrulline to L-arginine to synthesize NO via an argininosuccinate (AS) pathway.
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PMID:L-Citrulline recycle for synthesis of NO in cerebral perivascular nerves and endothelial cells. 1207 64

Endogenous nitric oxide (NO) is generated by nitric oxide synthases (NOSs), which convert arginine (Arg) and oxygen to citrulline (Cit) and NO. Cit can be enzymatically transformed back to Arg by argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL) via a pathway involving argininosuccinate (ArgSuc). Arg, Cit, and ArgSuc levels have been measured in single neurons, neuronal clusters, and neuropil from the nervous system of the common neurobiological model Aplysia californica. Using capillary electrophoresis with laser-induced fluorescence detection, ArgSuc was found to be present in the nervous system in millimolar concentrations at levels significantly exceeding Cit levels (p<0.01). ArgSuc levels are proportional to Arg concentrations in single neurons, whereas they have no clear correlation to the Cit or Arg/Cit ratio. NOS-expressing neurons often exhibit fixative-resistant nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) staining. Incubation of ganglia with Arg results in an increase in Cit and ArgSuc levels in the NADPH-d-positive neuropil with no effect on ArgSuc levels in NADPH-d-negative neurons, suggesting NOS activity in the neuropil. Similar incubation with Cit leads to decreased ArgSuc levels in NADPH-d-negative neurons. These results can be explained by localization of NOS and ASS in different neurons; therefore, the complete Arg-Cit-NO cycle may not be present in the same neuron. The surprisingly high intracellular ArgSuc concentration suggests alternative sources of ArgSuc and that at least a portion may be formed by the reverse reaction of ASL (catalyzing the conversion of Arg to ArgSuc), which can be inhibited by Cit.
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PMID:Ubiquitous presence of argininosuccinate at millimolar levels in the central nervous system of Aplysia californica. 1725 Jun 53