Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Chlorophyll b is an ubiquitous accessory pigment in land plants, green algae, and prochlorophytes. Its biosynthesis plays a key role in the adaptation to various light environments. We isolated six chlorophyll b-less mutants by insertional mutagenesis by using the nitrate reductase or argininosuccinate lyase genes as tags and examined the rearrangement of mutant genomes. We found that an overlapping region of a nuclear genome was deleted in all mutants and that this encodes a protein whose sequence is similar to those of methyl monooxygenases. This coding sequence also contains putative binding domains for a [2Fe-2S] Rieske center and for a mononuclear iron. The results demonstrate that a chlorophyll a oxygenase is involved in chlorophyll b formation. The reaction mechanism of chlorophyll b formation is discussed.
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PMID:Chlorophyll a oxygenase (CAO) is involved in chlorophyll b formation from chlorophyll a. 977 May 52

A comparative study of copper (Cu) toxicity and tolerance in two species of Ulva from Korea, the native Ulva pertusa and alien Ulva armoricana, was conducted by examining the effects on growth, pigmentation, chlorophyll fluorescence, antioxidant capacity and nitrate reductase activity. Toxic effects of Cu were less expressed in U. armoricana than in U. pertusa. At lower concentrations (25-50 microgL(-1)), exposure to Cu did not affect thallus growth of U. armoricana, whilst growth was significantly reduced in U. pertusa. An increase in chlorophyll concentrations was observed in U. armoricana exposed up to 100 microgL(-1), whereas Cu caused a significant chlorophyll reduction in U. pertusa. Chlorophyll b was reduced to a lesser extent than chlorophyll a by higher Cu concentrations. In U. armoricana, the maximum efficiency of photosystem II, minimum fluorescence, maximum electron transport rate and non-photochemical quenching were unaffected by Cu except at the highest concentration tested. U. pertusa showed a significant decrease in those parameters at much lower Cu concentrations. It was notable that in this alga the maximum efficiency of photosystem II was reduced at higher Cu concentrations than relative electron transport rate. Elevated concentrations of Cu induced a strong activation of antioxidant activity in U. armoricana, whereas the generation of high levels of reactive oxygen species probably decreased the non-enzymatic antioxidant defense system in U. pertusa. An increase in the nitrate reductase activity of U. armoricana at 50-100 microgL(-1) Cu coincided with the increase in chlorophyll contents, whereas U. pertusa showed a significant decrease at the higher Cu concentration. Differences in the sensitivity of the two species of Ulva to Cu may influence their competitive interactions in Korean coastal waters experiencing temporal increases in the loading of heavy metals.
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PMID:Physiological responses of Ulva pertusa and U. armoricana to copper exposure. 1808 44