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

Rat and feline brain and feline spinal cord were examined for the presence of semidehydroascorbate reductase (EC 1.6.5.4) and dehydroascorbate reductase (EC 1.8.5.1). Semidehydroascorbate reductase (SDAR), as monitored by both ascorbyl radical-dependent nicotinamide adenine dinucleotide (NADH) oxidase activity and NADH-dependent ascorbyl radical quenching, was present in all tissues studied. Rat cerebrum exhibited the highest levels and feline spinal cord the lowest. SDAR activity was about twice as high in feline cerebral cortex as in underlying white matter, and paralleled ascorbic acid levels. Subcellular fractionation of rat cerebrum localized most SDAR in a large granular fraction. In contrast, dehydroascorbate reductase was not detectable in any of the tissues examined. The results suggest that semidehydroascorbate reductase is the major enzyme catalyzing the regeneration of reduced ascorbic acid in the central nervous system.
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PMID:Reductive metabolism of ascorbic acid in the central nervous system. 399 84

Superoxide reductase from the hyperthermophilic anaerobe Pyrococcus furiosus uses electrons from reduced nicotinamide adenine dinucleotide phosphate, by way of rubredoxin and an oxidoreductase, to reduce superoxide to hydrogen peroxide, which is then reduced to water by peroxidases. Unlike superoxide dismutase, the enzyme that protects aerobes from the toxic effects of oxygen, SOR does not catalyze the production of oxygen from superoxide and therefore confers a selective advantage on anaerobes. Superoxide reductase and associated proteins are catalytically active 80 degrees C below the optimum growth temperature (100 degrees C) of P. furiosus, conditions under which the organism is likely to be exposed to oxygen.
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PMID:Anaerobic microbes: oxygen detoxification without superoxide dismutase. 1057 91

Ascorbic acid (AsA) maintains redox homeostasis by scavenging reactive oxygen species from prokaryotes to eukaryotes, especially plants. The enzyme monodehydroascorbate reductase (MDHAR) regenerates AsA by catalysing the reduction of monodehydroascorbate, using NADH or NADPH as an electron donor. The detailed recycling mechanism of MDHAR remains unclear due to lack of structural information. Here, we present the crystal structures of MDHAR in the presence of cofactors, nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+), and complexed with AsA as well as its analogue, isoascorbic acid (ISD). The overall structure of MDHAR is similar to other iron-sulphur protein reductases, except for a unique long loop of 63-80 residues, which seems to be essential in forming the active site pocket. From the structural analysis and structure-guided point mutations, we found that the Arg320 residue plays a major substrate binding role, and the Tyr349 residue mediates electron transfer from NAD(P)H to bound substrate via FAD. The enzymatic activity of MDHAR favours NADH as an electron donor over NADPH. Our results show, for the first time, structural insights into this preference. The MDHAR-ISD complex structure revealed an alternative binding conformation of ISD, compared with the MDHAR-AsA complex. This implies a broad substrate (antioxidant) specificity and resulting greater protective ability of MDHAR.
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PMID:Structure and catalytic mechanism of monodehydroascorbate reductase, MDHAR, from Oryza sativa L. japonica. 2765 77

Apple exocarp was used to investigate the effect of acibenzolar-S-methyl (ASM) and dehydroepiandrosterone (DHEA) treatments on reaction oxygen species (ROS) metabolism. The results indicated that ASM enhanced the hydrogen peroxide (H2O2) content, the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PDH). ASM also increased the contents of ascorbic acid (AsA), reduced glutathione (GSH) and nicotinamide ademine dinucleotidephosphate (NADPH), MdSOD and MdAPX expression, but decreased MdMDHAR and dehydroascorbate reductase (MdDHAR) expression. DHEA suppressed H2O2 accumulation and POD, APX, MDHAR, G6PDH activities, but increased SOD, CAT and GR activities compared to the control. ASM and DHEA treatments suppressed the contents of AsA, GSH and NADPH, and expression of MdSOD, MdAPX and MdMDHAR. These results suggest that DHEA treatment prevented ROS metabolism induced by ASM which showed the important role of G6PDH in maintaining redox homeostasis in apple exocarp.
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PMID:The role of glucose-6-phosphate dehydrogenase in reactive oxygen species metabolism in apple exocarp induced by acibenzolar-S-methyl. 3165 74