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In enzymology, a protochlorophyllide reductase () is an enzyme that catalyzes the chemical reaction :protochlorophyllide + NADPH + H+ chlorophyllide ''a'' + NADP+ Thus, the three substrates of this enzyme are protochlorophyllide, NADPH, and H+, whereas its 2 products are chlorophyllide a and NADP+ . This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is chlorophyllide-a:NADP+ 7,8-oxidoreductase. Other names in common use include NADPH2-protochlorophyllide oxidoreductase, NADPH-protochlorophyllide oxidoreductase, NADPH-protochlorophyllide reductase, protochlorophyllide oxidoreductase, and protochlorophyllide photooxidoreductase. This enzyme participates in porphyrin and chlorophyll metabolism. There are two structurally unrelated proteins with this activity, referred to as light-dependent and the dark-operative. The light-dependent reductase needs light to function, while the dark-operative version is a completely different protein, consisting of three subunits that exhibit significant sequence similarity to the three subunits of nitrogenase.〔Yuichi FujitaDagger and Carl E. Bauer (2000). Reconstitution of Light-independent Protochlorophyllide Reductase from Purified Bchl and BchN-BchB Subunits. J. Biol. Chem., Vol. 275, Issue 31, 23583-23588. ()〕 This enzyme might be evolutionary older but (being similar to nitrogenase) is highly sensitive to free oxygen and does not work if its concentration exceeds about 3%.〔S.Yamazaki, J.Nomata, Y.Fujita (2006) Differential operation of dual protochlorophyllide reductases for chlorophyll biosynthesis in response to environmental oxygen levels in the cyanobacterium ''Leptolyngbya boryana''. Plant Physiology, 2006, 142, 911-922 ()〕 Hence the alternative, light dependent version needed to evolve. ==References== * * 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Protochlorophyllide reductase」の詳細全文を読む スポンサード リンク
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