Protochlorophyllide reductase
From Wikipedia, the free encyclopedia
In enzymology, protochlorophyllide reductases (POR)[2][3] are enzymes that catalyze the conversion from protochlorophyllide to chlorophyllide a. They are oxidoreductases participating in the biosynthetic pathway to chlorophylls.[4][5]
This article is missing information about taxonomic distribution of EC 1.3.1.33; InterPro refs for both. (March 2022) |
light-dependent protochlorophyllide reductase | |||||||||
---|---|---|---|---|---|---|---|---|---|
Identifiers | |||||||||
EC no. | 1.3.1.33 | ||||||||
CAS no. | 68518-04-7 | ||||||||
Databases | |||||||||
IntEnz | IntEnz view | ||||||||
BRENDA | BRENDA entry | ||||||||
ExPASy | NiceZyme view | ||||||||
KEGG | KEGG entry | ||||||||
MetaCyc | metabolic pathway | ||||||||
PRIAM | profile | ||||||||
PDB structures | RCSB PDB PDBe PDBsum | ||||||||
Gene Ontology | AmiGO / QuickGO | ||||||||
|
light-independent protochlorophyllide reductase | |||||||||
---|---|---|---|---|---|---|---|---|---|
Identifiers | |||||||||
EC no. | 1.3.7.7 | ||||||||
Databases | |||||||||
IntEnz | IntEnz view | ||||||||
BRENDA | BRENDA entry | ||||||||
ExPASy | NiceZyme view | ||||||||
KEGG | KEGG entry | ||||||||
MetaCyc | metabolic pathway | ||||||||
PRIAM | profile | ||||||||
PDB structures | RCSB PDB PDBe PDBsum | ||||||||
|
There are two structurally unrelated proteins with this sort of activity, referred to as light-dependent (LPOR) and dark-operative (DPOR). The light- and NADPH-dependent reductase is part of the short-chain dehydrogenase/reductase (SDR) superfamily and is found in plants and oxygenic photosynthetic bacteria,[6][7] while the ATP-dependent dark-operative version is a completely different protein, consisting of three subunits that exhibit significant sequence and quaternary structure similarity to the three subunits of nitrogenase.[8] This enzyme may be evolutionary older; due to its bound iron-sulfur clusters is highly sensitive to free oxygen and does not function if the atmospheric oxygen concentration exceeds about 3%.[9] It is possible that evolutionary pressure associated with the great oxidation event resulted in the development of the light-dependent system.
The light-dependent version (EC 1.3.1.33) uses NADPH:
- protochlorophyllide + NADPH + H+ chlorophyllide a + NADP+
While the light-independent or dark-operative version (EC 1.3.7.7) uses ATP and ferredoxin:[10][11][12]
- protochlorophyllide a + reduced ferredoxin + 2 ATP + 2 H2O = chlorophyllide a + oxidized ferredoxin + 2 ADP + 2 phosphate