Engineered biosynthesis of bacteriochlorophyll b in Rhodobacter sphaeroides

Canniffe, Daniel P ORCID: 0000-0002-5022-0437 and Hunter, C Neil
(2014) Engineered biosynthesis of bacteriochlorophyll b in Rhodobacter sphaeroides. BIOCHIMICA ET BIOPHYSICA ACTA (BBA) - Bioenergetics, 1837 (10). pp. 1611-1616.

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Bacteriochlorophyll b has the most red-shifted absorbance maximum of all naturally occurring photopigments. It has a characteristic ethylidene group at the C8 position in place of the more common ethyl group, the product of a C8-vinyl reductase, which is carried by the majority of chlorophylls and bacteriochlorophylls used in photosynthesis. The subsequent and first step exclusive to bacteriochlorophyll biosynthesis, the reduction of the C7 = C8 bond, is catalyzed by chlorophyllide oxidoreductase. It has been demonstrated that the enzyme from bacteriochlorophyll a-utilizing bacteria can catalyze the formation of compounds carrying an ethyl group at C8 from both ethyl- and vinyl-carrying substrates, indicating a surprising additional C8-vinyl reductase function, while the enzyme from organisms producing BChl b could only catalyze C7 = C8 reduction with a vinyl substrate, but this product carried an ethylidene group at the C8 position. We have replaced the native chlorophyllide oxidoreductase-encoding genes of Rhodobacter sphaeroides with those from Blastochloris viridis, but the switch from bacteriochlorophyll a to b biosynthesis is only detected when the native conventional C8-vinyl reductase is absent. We propose a non-enzymatic mechanism for ethylidene group formation based on the absence of cellular C8-vinyl reductase activity.

Item Type: Article
Uncontrolled Keywords: Bacteriochlorophyll, Chlorophyll, Chlorophyllide oxidoreductase, Photosynthesis, Pathway engineering
Depositing User: Symplectic Admin
Date Deposited: 17 Jan 2019 08:22
Last Modified: 19 Jan 2023 01:06
DOI: 10.1016/j.bbabio.2014.07.011
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