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Stereoselective C3‐substituent modification and substrate channeling by oxidoreductase BchC in bacteriochlorophyll a biosynthesis
Author(s) -
Teramura Misato,
Tsukatani Yusuke,
Harada Jiro,
Hirose Mitsuaki,
Tamiaki Hitoshi
Publication year - 2019
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1002/1873-3468.13372
Subject(s) - bacteriochlorophyll , rhodobacter , biosynthesis , oxidoreductase , nad+ kinase , chemistry , stereochemistry , epimer , enzyme , cofactor , biochemistry , photosynthesis , mutant , gene
We report the in vitro activity of recombinant BchC oxidoreductase involved in bacteriochlorophyll a biosynthesis. BchC of Rhodobacter capsulatus preferentially oxidizes 3 1 R ‐3‐(1‐hydroxyethyl)‐chlorophyllide a and 3 1 R ‐3‐(1‐hydroxyethyl)‐bacteriochlorophyllide a in the presence of NAD + to 3‐acetyl‐chlorophyllide a and bacteriochlorophyllide a , respectively, leaving the unreacted 3 1 S ‐epimers. In the reverse reaction, BchC with NADH predominately produces 3 1 R ‐epimeric alcohols from the 3‐acetyl‐(bacterio)chlorins. BchC of Chlorobaculum tepidum demonstrates the same 3 1 R ‐selectivity, suggesting that utilization of 3 1 R ‐epimers in BchC‐catalyzed reductions may be conserved across different phyla of photosynthetic bacteria. Additionally, the presence of BchC accelerates the 3‐vinyl hydration by BchF hydratase of Chlorobaculum tepidum during conversion of chlorophyllide a to 3‐acetyl‐chlorophyllide a through 3‐(1‐hydroxyethyl)‐chlorophyllide a , indicating that these enzymes work cooperatively to promote efficient bacteriochlorophyll a biosynthesis.