Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.5.4 (SOR)
 720 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Coated vesicles were isolated from rat liver in about 80% fraction purity as determined from electron microscopy and analyses of marker enzymes and compared with Golgi apparatus and other membrane fractions isolated in parallel. The fractions were enriched in NADH-monodehydroascorbate reductase, ascorbate oxidase and ascorbic acid. The NADH-monodehydroascorbate reductase and ascorbate oxidase of the Golgi apparatus and coated vesicles differed from that of the endoplasmic reticulum in being inhibited by the sodium selective ionophore, monensin, at physiological concentrations while these activities were stimulated by ethylenediaminetetraacetic acid in coated vesicles but not in Golgi apparatus. Activities of both coated vesicles and Golgi apparatus fractions depleted in the coat protein, clathrin, were activated by the addition of clathrin-rich supernatant fractions. The results are discussed in the context of monodehydroascorbate as an acceptor for electron transport-mediated transfer of electrons from NADH by coated vesicles as part of a possible mechanism to drive membrane translocations or to acidify the interiors of vesicles.
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PMID:Monodehydroascorbate as an electron acceptor for NADH reduction by coated vesicle and Golgi apparatus fractions of rat liver. 614 8

NADH semidehydroascorbate oxidoreductase activity is present in clathrin coated vesicles isolated from rat liver. The activity of the enzyme on the coated vesicles and Golgi apparatus but not that of endoplasmic reticulum is stimulated by calmodulin and is inhibited by three different drugs which are known inhibitors of calmodulin function including trifluoperizine, pimozide and R24571. Extraction of clathrin from the vesicles causes a decrease in activity which can be partially restored when the extracted clathrin is added back. Added calmodulin also restores much of the activity which is lost when the clathrin is removed and the specific activity of added pure calmodulin is similar to that of the crude clathrin on a protein basis. There is a decrease in enzyme activity if coated vesicles or Golgi apparatus are treated with a calcium antagonist (8-[N,N-diethylamino]-octyl-3,4,5-trimethoxybenzoate) (TMB-8). However, the enzyme activity can be recovered to that of the untreated control if calcium (6.0 mM) is added. An additive stimulatory effect on enzyme activity is also observed when both calcium (1.0 mM) and calmodulin (40 micrograms/ml) are present in the vesicles simultaneously. The results show that the NADH-semidehydroascorbate oxidoreductase of coated vesicles and Golgi apparatus have regulatory properties different from those of the microsomal electron transport system. Calmodulin-calcium control mediated through the semidehydroascorbate reductase, may be among the components that regulate Golgi apparatus secretion.
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PMID:Calmodulin-NADH semidehydroascorbate oxidoreductase interactions of clathrin coated vesicles. 662 33

Hereditary methemoglobinemia with generalized deficiency of NADH-cytochrome b5 reductase (b5R) (type II) is a rare disease characterized by severe developmental abnormalities, which often lead to premature death. Although the molecular relationship between the symptoms of this condition and the enzyme deficit are not understood, it is thought that an important cause is the loss of the lipid metabolizing activities of the endoplasmic reticulum-located reductase. However, the functions of the form located on outer mitochondrial membranes have not been considered previously. In this study, we have analyzed the gene of an Italian patient and identified a novel G-->T transversion at the splice-acceptor site of the 9th exon, which results in the complete absence of immunologically detectable b5R in blood cells and skin fibroblasts. In cultured fibroblasts of the patient, NADH-dependent cytochrome c reductase, ferricyanide reductase, and semidehydroascorbate reductase activities were severely reduced. The latter activity is known to be due to b5R located on outer mitochondrial membranes. Thus, our results demonstrate that the reductase in its two membrane locations, endoplasmic reticulum and outer mitochondrial membranes, is the product of the same gene and suggest that a defect in ascorbate regeneration may contribute to the phenotype of hereditary methemoglobinemia of the generalized type.
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PMID:A novel point mutation in a 3' splice site of the NADH-cytochrome b5 reductase gene results in immunologically undetectable enzyme and impaired NADH-dependent ascorbate regeneration in cultured fibroblasts of a patient with type II hereditary methemoglobinemia. 766 55

Outer mitochondrial membrane cytochrome b5 (OMb) originally found in rat liver is an isoform of cytochrome b5 (b5) of the endoplasmic reticulum. In contrast to accumulated data on the physiological roles of b5, functions of OMb have not been well characterized except for its involvement in regeneration of ascorbic acid [i.e., in a semidehydroascorbate reductase (SDAR) system]. By using highly specific antibodies against rat OMb, we found immunohistochemically that OMb in the rat adrenal gland was most abundant in the zona glomerulosa (zG) among the three cortical zones, and the expression level was enhanced on angiotensin II-stimulation. SDAR activity was found in zG and inhibited by anti-OMb antibody. Moreover, the increase in plasma aldosterone concentration under Na+ -deficiency was suppressed by limited ascorbic acid (Asc) availability in rat mutants unable to synthesize Asc, while plasma corticosterone concentration was not affected. These data suggest that OMb, present abundantly in zG, participates in aldosterone formation in zG of rat under angiotensin II-stimulation through regeneration of Asc.
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PMID:Possible participation of outer mitochondrial membrane cytonchrome B5 in steroidogenesis in zona glomerulosa of rat adrenal cortex. 1566 5

Redox activities, NADH:ferricyanide reductase, NAD(P)H:cytochrome reductases, and NADH:ascorbate free-radical reductase, are present in endoplasmic reticulum (ER) and glyoxysomal membranes from the endosperm of germinating castor bean (Ricinus comminus L. var Hale). The development of these functions was followed in glyoxysomes and ER isolated on sucrose gradients from castor bean endosperm daily from 0 through 6 days of germination. On a per seed basis, glyoxysomal and ER protein, glyoxysomal and ER membrane redox enzyme activities, and glyoxylate cycle activities peaked at day 4 as did the ER membrane content of cytochrome P-450. NADH:ferricyanide reductase was present in glyoxysomes and ER isolated from dry seed. This activity increased only about twofold in glyoxysomes and threefold in ER during germination relative to the amount of protein in the respective fractions. The other reductases, NADH:cytochrome reductase and NADH:ascorbate free-radical reductase, increased about 10-fold in the ER relative to protein up to 4 to 5 days, then declined. NADPH:cytochrome reductase reached maximum activity relative to protein at day 2 in both organelles. The increases in redox activities during germination indicate that the membranes of the ER and glyoxysome are being enriched with redox proteins during their development. The development of redox functions in glyoxysomes was found to be coordinated with development of the glyoxylate cycle.
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PMID:Development of Endoplasmic Reticulum and Glyoxysomal Membrane Redox Activities during Castor Bean Germination. 1666 25