Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.10.3.3 (ascorbate oxidase)
 778 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Experiments were carried out to evaluate the production of hydroxyl radical-like species by intact rat liver cells by assaying for the production of ethylene from alpha-keto-4-thiomethylbutyric acid in the absence and presence of added iron. In the absence of iron, a low rate of ethylene production, which was not sensitive to superoxide dismutase, catalase, or competitive scavengers was observed. Ethylene was produced when KMBA was incubated with perfusates of rat liver or the suspension medium obtained after incubating liver cells for varying periods of time, followed by removal of the liver cells. Boiling the perfusate or suspension medium had no effect on ethylene production. This ethylene production does not appear to reflect an oxygen radical-mediated event. The addition of ferric-EDTA, but not ferric-desferrioxamine, increased ethylene production by the hepatocyte suspensions in a reaction sensitive to inhibition by catalase, ascorbate oxidase, and competitive scavengers, but not superoxide dismutase. The sensitivity to externally added catalase and ascorbate oxidase suggested that the ethylene production reflected an extracellular oxygen radical generating system. Ferric alone and several ferric chelates, for example, ferric-ATP, ADP, AMP, histidine, and citrate stimulated ethylene production using perfusates of liver or suspension medium after removal of the hepatocytes. The sensitivity of the added iron system to ascorbate oxidase suggested that during perfusion or incubation of liver cells, efflux of ascorbate occurs, followed by reduction of the iron and subsequently, extracellular production of oxygen radicals.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Ethylene production from alpha-keto-4-thiomethylbutyric acid by isolated rat liver cells, suspension medium, and perfusates in the absence and presence of iron. 301 75

The ascorbate content declined rapidly in broccoli (Brassica oleracea L. var. italica) florets, but not in the stem tissue, during post-harvest senescence. Ascorbate peroxidase (APX), ascorbate oxidase (AO), l-galactono-1,4-lactone dehydrogenase (GLDH), monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were investigated in gene expression after harvest in both florets and the stem tissue of broccoli. Cytosolic gene expressions (BO-APX 1, BO-APX 2, BO-AO, BO-MDAR 2, and BO-GR) were stimulated actively in broccoli florets after harvest. By contrast, it was observed that mRNA levels of chloroplastic APX, BO-sAPX and BO-tbAPX, had decreased by 12 h after harvest in broccoli florets, suggesting that the active oxygen species (AOS) scavenging system in chloroplasts was largely abolished in florets during the early hours of the post-harvest period. In addition, gene expressions in GLDH and other chloroplastic enzymes such as BO-MDAR 1 and BO-DHAR decreased rapidly within 24 h after harvest. Ethylene treatment had no effect on the ascorbate level and the expression of all genes investigated. The expressions of BO-GLDH and chloroplastic genes (BO-sAPX, BO-tbAPX, BO-MDAR 1, and BO-DHAR) mRNA were suppressed by treatment with methyl jasmonate (MJ) and abscisic acid (ABA) and were accompanied by the acceleration of ascorbate degradation. These data suggest that ascorbate metabolism tends to be inactivated in chloroplasts by transcriptional regulation, but not in the cytosol, when ascorbate decreases under stress conditions.
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PMID:Ascorbate metabolism in harvested broccoli. 1451 88