Protochlorophyllide reductase

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.^[1] 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%.^[2] Hence the alternative, light dependent version needed to evolve.

References

↑ 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.
↑ 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

Apel K, Santel HJ, Redlinger TE, Falk H (1980). "The protochlorophyllide holochrome of barley (Hordeum vulgare L.) Isolation and characterization of the NADPH:protochlorophyllide oxidoreductase". Eur. J. Biochem. 111 (1): 251–8. doi:10.1111/j.1432-1033.1980.tb06100.x. PMID 7439188.
Griffiths WT (1978). "Reconstitution of chlorophyllide formation by isolated etioplast membranes". Biochem. J. 174 (3): 681–92. PMC 1185970. PMID 31865.

Oxidoreductases: CH–CH oxidoreductases (EC 1.3)

1.3.1: NAD/NADP acceptor	Enoyl-acyl carrier protein reductase/Enoyl ACP reductase 7-Dehydrocholesterol reductase Biliverdin reductase 2,4 Dienoyl-CoA reductase Dihydroxymethyloxo-tetrahydroquinoline dehydrogenase

1.3.3: Oxygen acceptor	Dihydroorotate dehydrogenase Coproporphyrinogen III oxidase Protoporphyrinogen oxidase Bilirubin oxidase Acyl-CoA oxidase Dihydrouracil oxidase Tetrahydroberberine oxidase Secologanin synthase Tryptophan alpha,beta-oxidase Pyrroloquinoline-quinone synthase L-galactonolactone oxidase

1.3.5: Quinone	Succinate dehydrogenase SDHA SDHB SDHC SDHD

1.3.99: Other acceptors	Fumarate reductase Butyryl-CoA dehydrogenase Acyl CoA dehydrogenase ACADSB ACADS 5α-reductase SRD5A1 SRD5A2 SRD5A3 Glutaryl-CoA dehydrogenase Isovaleryl coenzyme A dehydrogenase 3-oxo-5beta-steroid 4-dehydrogenase

Enzymes

Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Catalytically perfect enzyme Coenzyme Cofactor Enzyme catalysis Enzyme kinetics Lineweaver–Burk plot Michaelis–Menten kinetics

Regulation	Allosteric regulation Cooperativity Enzyme inhibitor

Classification	EC number Enzyme superfamily Enzyme family List of enzymes

Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list)

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