Bacteriochlorophylls a, b, and g are bacteriochlorins, meaning their molecules have a bacteriochlorin macrocycle ring with two reducedpyrrole rings (B and D). Bacteriochlorophylls c, d, e, and f are chlorins, meaning their molecules have a chlorin macrocycle ring with one reduced pyrrole ring (D).[4]
Bacteriochlorophylls c to f occur in the form of closely related homologs with different alkyl groups attached to pyrrole rings B and C and are illustrated above in their simplest versions, esterified with the sesquiterpene alcohol farnesol.[5] Most of the variation occurs in the 8 and 12 positions and can be attributed to methyltransferase variation.[6] BChl cS is a term for 8-ethyl,12-methyl homolog of BChl c.[7]
Bacteriochlorophyll g has a vinyl group in ring (A), at position 8.[8]
Biosynthesis
There are a large number of known bacteriochlorophylls[4][9] but all have features in common since the biosynthetic pathway involves chlorophyllide a (Chlide a) as an intermediate.[10]
Chlorin-cored BChls (c to f) are produced by a series of enzymatic modifications on the sidechain of Chlide a, much like how Chl b, d, e are made. The bacteriochlorin-cored BChls a, b, g require a unique step to reduce the double bound between C7 and C8, which is performed by Chlorophyllide a reductase (COR).[9]
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^ a bBryant DA, et al. (2007-07-27), "Candidatus Chloracidobacterium thermophilum: An Aerobic Phototrophic Acidobacterium", Science, 317 (5837): 523–526, Bibcode:2007Sci...317..523B, doi:10.1126/science.1143236, PMID 17656724, S2CID 20419870
^Vogl K, et al. (2012-08-10). "Bacteriochlorophyll f: properties of chlorosomes containing the "forbidden chlorophyll"". Front. Microbiol. 3: article 298, pages 1–12. doi:10.3389/fmicb.2012.00298. PMC 3415949. PMID 22908012.
^ a bSenge, Mathias O.; Smith, Kevin M. (2004). "Biosynthesis and Structures of the Bacteriochlorophylls". Anoxygenic Photosynthetic Bacteria. Advances in Photosynthesis and Respiration. Vol. 2. pp. 137–151. doi:10.1007/0-306-47954-0_8. ISBN 0-7923-3681-X.
^Harada, Jiro; Shibata, Yutaka; Teramura, Misato; Mizoguchi, Tadashi; Kinoshita, Yusuke; Yamamoto, Ken; Tamiaki, Hitoshi (2018). "In Vivo Energy Transfer from Bacteriochlorophyll c , d , e , or f to Bacteriochlorophyll a in Wild-Type and Mutant Cells of the Green Sulfur Bacterium Chlorobaculum limnaeum". ChemPhotoChem. 2 (3): 190–195. doi:10.1002/cptc.201700164.
^Gomez Maqueo Chew, A; Frigaard, NU; Bryant, DA (September 2007). "Bacteriochlorophyllide c C-8(2) and C-12(1) methyltransferases are essential for adaptation to low light in Chlorobaculum tepidum". Journal of Bacteriology. 189 (17): 6176–84. doi:10.1128/JB.00519-07. PMC 1951906. PMID 17586634.
^Gloe, A; Risch, N (1 August 1978). "Bacteriochlorophyll cs, a new bacteriochlorophyll from Chloroflexus aurantiacus". Archives of Microbiology. 118 (2): 153–6. doi:10.1007/BF00415723. PMID 697505. S2CID 20011765.
^Tsukatani, Yusuke; Yamamoto, Haruki; Mizoguchi, Tadashi; Fujita, Yuichi; Tamiaki, Hitoshi (2013). "Completion of biosynthetic pathways for bacteriochlorophyll g in Heliobacterium modesticaldum: The C8-ethylidene group formation". Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1827 (10): 1200–1204. doi:10.1016/j.bbabio.2013.06.007. PMID 23820336.
^ a bChew, Aline Gomez Maqueo; Bryant, Donald A. (2007). "Chlorophyll Biosynthesis in Bacteria: The Origins of Structural and Functional Diversity". Annual Review of Microbiology. 61: 113–129. doi:10.1146/annurev.micro.61.080706.093242. PMID 17506685.
^Willows, Robert D. (2003). "Biosynthesis of chlorophylls from protoporphyrin IX". Natural Product Reports. 20 (6): 327–341. doi:10.1039/B110549N. PMID 12828371.
^Battersby, Alan R. (2000). "Tetrapyrroles: The pigments of life: A Millennium review". Natural Product Reports. 17 (6): 507–526. doi:10.1039/B002635M. PMID 11152419.