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Chlorophyllide a, (R=H). In chlorophyllide b, the methyl group show in the green box is replaced with a formyl group. Chlorophyllide a, is a carboxylic acid (R=H). In chlorophyllide b, the methyl group at position 13 (IUPAC numbering for chlorophyllide a) and highlighted in the green box, is replaced with a formyl group.
This conversion forms an ester of the carboxylic acid group in chlorophyllide a with the 20-carbon diterpene alcohol phytol. Chlorophyll b is made by the same enzyme acting on chlorophyllide b. The same is known for chlorophyll d and f, both made from corresponding chlorophyllides ultimately made from chlorophyllide a. [39]
The systematic name of this enzyme class is chlorophyllide-a:NADP+ oxidoreductase. Other names in common use include 3,8-divinyl protochlorophyllide a 8-vinyl-reductase, [4-vinyl]chlorophyllide a reductase, and 4VCR. This enzyme is part of the biosynthetic pathway to chlorophylls. Protochlorophyllide, the product of the reaction
Chlorophyllide a, (R=H) is converted to chlorophyllide b, in which the methyl group show in the green box is oxidised to a formyl group. This enzyme contains a mononuclear iron centre and is part of the biosynthetic pathway to chlorophylls .
The enzyme that converts protochlorophyllide to chlorophyllide a, the next intermediate on the biosynthetic pathway, [4] is protochlorophyllide reductase, [5] EC 1.3.1.33. There are two structurally unrelated proteins with this activity: the light-dependent and the dark-operative. The light-dependent reductase needs light to operate.
Chlorophyllide a reductase (EC 1.3.7.15), also known as COR, is an enzyme with systematic name bacteriochlorophyllide-a:ferredoxin 7,8-oxidoreductase. [ 1 ] [ 2 ] It catalyses the following chemical reaction
Pheophytin a, i.e. chlorophyll a without the Mg 2+ ion.. Pheophytin or phaeophytin is a chemical compound that serves as the first electron carrier intermediate in the electron transfer pathway of Photosystem II (PS II) in plants, and the type II photosynthetic reaction center (RC P870) found in purple bacteria.
A negation is a negative polarity item, abbreviated NPI or NEG. The linguistic environment in which a polarity item appears is a licensing context. In the simplest case, an affirmative statement provides a licensing context for a PPI, while negation provides a licensing context for an NPI. However, there are many complications, and not all ...