EC Number   |
General Information |
Reference |
|---|
   1.3.7.2 | evolution |
ferredoxin-dependent bilin reductases (FDBRs) are a class of enzymes reducing the heme metabolite biliverdin IXa (BV) to form open-chain tetrapyrroles used for light-perception and light-harvesting in photosynthetic organisms. Evolution and molecular mechanism of four-electron reducing ferredoxin-dependent bilin reductases from oceanic phages, overview. PcyX is originally identified from metagenomics data derived from phage. PcyA (EC 1.3.7.2) is the closest relative catalysing the reduction of biliverdin (BV) to phycocyanobilin. But PcyX converts the same substrate to phycoerythrobilin, resembling the reaction catalysed by cyanophage PebS. But the change in regiospecificity from PcyA to PcyX is not only caused by individual catalytic amino acid residues. Rather the combination of the architecture of the active site with the positioning of the substrate triggers specific proton transfer yielding the individual phycobilin products. Phylogenetic analysis and tree suggest PcyX sequences forming a distinct clade |
763016 |
| 1.3.7.2 | evolution |
the enzyme belongs to the ferredoxin-dependent bilin reductase family. All members of the FDBR family are radical enzymes |
-, 724228 |
| 1.3.7.2 | metabolism |
during the biosynthesis of light-harvesting phycobilins in cyanobacteria, two members of the ferredoxin-dependent bilin reductases are involved in the reduction of the open-chain tetrapyrrole biliverdin IXa to the pink pigment phycoerythrobilin. The first reaction is catalyzed by 15,16-dihydrobiliverdin:ferredoxin oxidoreductase (PebA) and produces the unstable intermediate 15,16-dihydrobiliverdin (DHBV). This intermediate is subsequently channeled to and converted by phycoerythrobilin:ferredoxin oxidoreductase to the final product phycoerythrobilin. An on-column assay employing immobilized enzyme in combination with UV-Vis and fluorescence spectroscopy reveals that both enzymes transiently interact and that transfer of the intermediate is facilitated by a significantly higher binding affinity of DHBV toward phycoerythrobilin:ferredoxin oxidoreductase (PebB, EC 1.3.7.3). The intermediate DHBV is transferred via proximity channeling |
763020 |
| 1.3.7.2 | metabolism |
PebB, phycoerythrobilinPEB:ferredoxin oxidoreductase, EC 1.3.7.3, acts in tandem with PebA, 15,16-DHBV:ferredoxin oxidoreductase, which reduces biliverdin IXalpha at the C15-C16 double bond to produce 15,16-dihydrobiliverdin. Both enzymes function in close contact for metabolic channeling of 15,16-dihydrobiliverdin |
-, 724228 |
| 1.3.7.2 | metabolism |
phycobilins are light-harvesting pigments of cyanobacteria, red algae, and cryptophytes. The biosynthesis of phycoerythrobilin (PEB) is catalyzed by the subsequent action of two ferredoxin-dependent bilin reductases (FDBRs). 15,16-Dihydrobiliverdin (DHBV):ferredoxin oxidoreductase (PebA) catalyzes the two-electron reduction of biliverdin IXalpha to 15,16-DHBV, and PEB:ferredoxin oxidoreductase (PebB) reduces this intermediate further to PEB. The biosynthetic intermediate DHBV is transferred via proximity channeling to PEB:ferredoxin oxidoreductase (PebB) |
763264 |
| 1.3.7.2 | more |
a conserved aspartate-histidine pair is critical for activity of PcyA. PcyA contains the catalytic Asp-His-Glu triad. Strutcure comparisons of FDBRs, PcyA and PcyX, overview. Ile86 in PcyA is replaced by Met67, whereas Val90 is substituted by Cys71 in PcyX. Both are strictly conserved in all PcyX sequences, but small hydrophobic residues in all other FDBR. Due to the disorder on the distal side of the binding pocket, residues corresponding to Asn219 in PcyA or to Asp206 in PebS are not visible in our PcyX structure. Glu76 of PcyA is central for exovinyl-reduction |
763016 |
| 1.3.7.2 | more |
structure comparisons of Synechococcus WH8020 PebA and Guillardia theta PebB, overview. The Asp-99/Asp-219 pair is structurally conserved in most FDBRs, while the corresponding residues are relevant for PebB, for PebA only the homologue of Asp99 (Asp84) is essential for catalytic activity. The homologue of Asp219 (Asp205) is not essential and is rotated out of the active site. PebB binds DHBV analogous to the binding of BV in PebA/PebS |
763264 |
| 1.3.7.2 | more |
the highly conserved aspartate residue Asp105 is critical for the reduction. In addition to the importance of certain catalytic residues, the shape of the active site and consequently the binding of the substrate highly determines the catalytic properties |
-, 724228 |
| 1.3.7.2 | physiological function |
phycobilins are light-harvesting pigments of cyanobacteria, red algae, and cryptophytes. The biosynthesis of phycoerythrobilin (PEB) is catalyzed by the subsequent action of two ferredoxin-dependent bilin reductases (FDBRs). 15,16-Dihydrobiliverdin (DHBV):ferredoxin oxidoreductase (PebA) catalyzes the two-electron reduction of biliverdin IXalpha to 15,16-DHBV, and PEB:ferredoxin oxidoreductase (PebB) reduces this intermediate further to PEB |
763264 |
