1.1.1.294: chlorophyll(ide) b reductase
This is an abbreviated version!
For detailed information about chlorophyll(ide) b reductase, go to the full flat file.
Word Map on EC 1.1.1.294
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1.1.1.294
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stay-green
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oxygenase
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light-harvesting
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pheophorbide
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7-hydroxymethyl
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dark-induced
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thylakoids
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ryegrass
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lhcii
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lolium
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perenne
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perennial
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etioplasts
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grana
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pheophytinase
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pao
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chlorophyll-binding
- 1.1.1.294
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stay-green
- oxygenase
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light-harvesting
- pheophorbide
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7-hydroxymethyl
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dark-induced
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thylakoids
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ryegrass
- lhcii
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lolium
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perenne
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perennial
- etioplasts
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grana
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pheophytinase
- pao
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chlorophyll-binding
Reaction
Synonyms
BoNYC1, CBR, Chl b reductase, chlorophyll b reductase, chlorophyll(ide) b reductase, LpNYC1, More, NOL, NON-YELLOW COLORING 1, NON-YELLOW COLORING1, NYC-like, NYC1, NYC1-LIKE
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1.1.1.294 chlorophyll(ide) b reductaseAdvanced search results
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General Information on EC 1.1.1.294 - chlorophyll(ide) b reductase
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GENERAL INFORMATION 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
evolution
malfunction
metabolism
physiological function
additional information
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rice mutants lacking either NYC1 or NOL are deficient in chlorophyll b reductase activity during leaf senescence. Recombinant NOL enzyme shows in vitro chlorophyll b reductase activity in the absence of NYC1, it is possible that NOL could function independently of NYC1. It is possible that the heterodimer formation of NYC1 and NOL is necessary only under specific developmental conditions such as leaf senescence
evolution
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chlorophyll b reductase belongs to the short-chain dehydrogenase superfamily
evolution
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chlorophyll b reductase belongs to the short-chain dehydrogenase superfamily
evolution
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chlorophyll b reductase belongs to the short-chain dehydrogenase superfamily
evolution
LpNYC1 shares the highest amino acid sequence similarity with BdNYC1 (91.5%) in Brachypodium distachyon, and the lowest with Arabidopsis NYC1 (63.6%). Despite the sequence divergence, the NYC1 orthologues all share the classical chloroplast-localized short-chain dehydrogenase/reductase (SDR) domain with the TGXXGXXG cofactor binding motif and the YXXXK active site for catabolizing Chl b into 7-hydroxymethyl-chl a
malfunction
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Arabidosis thaliana mutants lacking either NYC1 or NOL are deficient in chlorophyll b reductase activity during leaf senescence. Impairment in the chlorophyll b reduction leads to LHC stabilization during leaf senescence in the rice mutant lacking chlorophyll b reductase
malfunction
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germination rates of mutants rapidly decrease during storage, the non-yellow coloring1 (nyc1)/nyc1-like (nol) mutant seeds fail to germinate after storage for 23 months, whereas 75% of the wild-type seeds germinate after 42 months. Mutations in the chlorophyll degradation enzymes, e.g. in chlorophyll b reductase, result in the stay-green phenotype in leaves, only a nyc1 mutation was accompanied by a stay-green phenotype in Arabidopsis thaliana. Lack of chlorophyll b reductase results in the retention of LHC proteins as well as both chlorophyll a and b that are associated with LHC proteins in leaves. Large amount of LHCII apoproteins accumulated in the nyc1 and nyc1/nol mutants
malfunction
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rice mutants lacking either NYC1 or NOL are deficient in chlorophyll b reductase activity during leaf senescence. Impairment in the chlorophyll b reduction leads to LHC stabilization during leaf senescence in the rice mutant lacking chlorophyll b reductase
malfunction
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in broccoli, treatments with UV-C can delay Chl degradation, diminish respiration rates and reduce the loss of sugars and proteins during postharvest storage
malfunction
knocking out the Chl b reductase gene might lead to a stay-green phenotype. Overexpression of LpNYC1 activates leaf senescence in Nicotiana benthamiana and rescues the stay-green trait in the Arabidopsis thaliana nyc1 null mutant
metabolism
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the enzyme is part of the chlorophyll metabolism pathway, overview. Chlorophyll b reductase catalyzes the conversion of chlorophyll b to 7-hydroxymethyl chlorophyll a, which is the first step in chlorophyll b degradation
metabolism
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three enzymes participating in the chlorophyll cycle, namely, chlorophyllide a oxygenase, chlorophyll b reductase, and 7-hydroxymethylchlorophyll reductase, overview. In the reverse reactions from chlorophyll b to chlorophyll a, the 7-formyl group of chlorophyll b is first reduced to a hydroxyl group by the action of chlorophyll b reductase. The activities of chlorophyll b reductase and7-hydroxymethylchlorophyll reductase are coordinated in their regulation, otherwise, imbalance of those activities may lead to accumulation of the intermediate of the pathway. The conversion of chlorophyll b into chlorophyll a precedes the degradation of LHC during leaf senescence
metabolism
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three enzymes participating in the chlorophyll cycle, namely, chlorophyllide a oxygenase, chlorophyll b reductase, and 7-hydroxymethylchlorophyll reductase, overview. In the reverse reactions from chlorophyll b to chlorophyll a, the 7-formyl group of chlorophyll b is first reduced to a hydroxyl group by the action of chlorophyll b reductase. The activities of chlorophyll b reductase and7-hydroxymethylchlorophyll reductase are coordinated in their regulation, otherwise, imbalance of those activities may lead to accumulation of the intermediate of the pathway. The conversion of chlorophyll b into chlorophyll a precedes the degradation of LHC during leaf senescence
metabolism
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three enzymes participating in the chlorophyll cycle, namely, chlorophyllide a oxygenase, chlorophyll b reductase, and 7-hydroxymethylchlorophyll reductase, overview. In the reverse reactions from chlorophyll b to chlorophyll a, the 7-formyl group of chlorophyll b is first reduced to a hydroxyl group by the action of chlorophyll b reductase. The activities of chlorophyll b reductase and7-hydroxymethylchlorophyll reductase are coordinated in their regulation, otherwise, imbalance of those activities may lead to accumulation of the intermediate of the pathway. The conversion of chlorophyll b into chlorophyll a precedes the degradation of LHC during leaf senescence
metabolism
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during senescence, chlorophylls are degraded with the purpose of avoiding presence of photoactive molecules. Chlorophyll b must be previously converted to chlorophyll a in order to be catabolized. This reduction process is catalyzed by two enzymes, chlorophyll b reductase (CBR) and hydroxymethyl chlorophyll a reductase (HCAR)
physiological function
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chlorophyll b reductase plays an essential role in maturation and storability of seeds. Both isozymes NYC1 and NOL participate in chlorophyll degradation during seed maturation
physiological function
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when greening seedlings are transferred back to darkness, conversion of chlorophyll b to chlorophyll a occurs, which results in degradation of LHC and an increase in the core antenna complexes
physiological function
inflorescence degreening is associated with increased mRNA abundance of NYC1, pheophytin pheophorbide hydrolase and pheophorbide a oxygenase. Mutants of NYC1 show preferential retention of chlorophyll b during dark incubation
physiological function
isoform NYC1 degrades the chlorophyll b on photosystem II under high-light conditions, thus decreasing the photosystem II content. During high-light treatment, the chlorophyll a/b ratio is stable in the wild-type and plants lacking NYC1-Like (NOL) activity, and the photosystem II content decreases in wiild-type plants. The chlorophyll a/b ratio decreases in the NYC1 and NYC1/NOL deficient plants, and a substantial degree of photosystem II is retained in NYC1/NOL deficient plants after the high-light treatment
physiological function
NOL is not the primary enzyme responsible for degradation. During high-light treatment, the chlorophyll a/b ratio is stable in the wild-type and plants lacking NYC1-Like (NOL) activity, and the photosystem II content decreases in wiild-type plants. The chlorophyll a/b ratio decreases in NYC1/NOL deficient plants, and a substantial degree of photosystem II is retained in NYC1/NOL deficient plants after the high-light treatment
physiological function
when the level of chlorophyll b is enhanced by the introduction of a truncated chlorophyllide a oxygenase gene and leaves are incubated in the dark, the amount of NYC1 is greatly increased compared while the amount of NYC1 mRNA is the same as in the wild type. In contrast, NYC1 does not accumulate in the mutant without chlorophyll b. The NYC1 level is related to the energetically uncoupled light-harvesting chlorophyll a/b protein complex
physiological function
chlorophyll (Chl) degradation leads to leaf senescence and adversely affects biomass production of forage grasses and aesthetic appearance of turfgrasses. Transcriptional regulation of chlorophyll b reductase gene non-yellow coloring 1 associated with leaf senescence in perennial ryegrass. Predicted functional roles of LpNYC1 in Chl catabolism in green tissues and in leaf senescence. LpNYC1 catalyzes Chl degradation. Upstream transcription factors from Lolium perenne, LpABI5, LpABF3, and LpEIN3, directly regulating the expression of LpNYC1 in perennial ryegrass during leaf senescence
physiological function
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chlorophyll molecules (Chl a and Chl b) are located in the thylakoid membranes inside the chloroplasts forming part of the light-harvesting chlorophyll a/b-protein complex of photosystem II (LHCII). During senescence, thylakoid membranes are dismantled and chlorophyll molecules are released and catabolized. Chlorophyll degradation is under strict control because free chlorophyll molecules or their intermediates are photoactive and can generate highly reactive toxic radicals. During senescence, chlorophylls are degraded, therefore chlorophyll b must be previously converted to chlorophyll a in order to be catabolized. This reduction process is catalyzed by two enzymes, chlorophyll b reductase (CBR) and hydroxymethyl chlorophyll a reductase (HCAR). Chlorophyll b degradation is required for the degradation of light-harvesting complex II and thylakoid grana during leaf senescence
