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Kent Academic Repository Full text document (pdf) Citation for published version Bryant, Donald A. and Hunter, C. Neil and Warren, Martin J. (2020) Biosynthesis of the modified tetrapyrroles: the pigments of life. Journal of Biological Chemistry . ISSN 0021-9258. DOI https://doi.org/10.1074/jbc.REV120.006194 Link to record in KAR https://kar.kent.ac.uk/80865/ Document Version Author's Accepted Manuscript Copyright & reuse Content in the Kent Academic Repository is made available for research purposes. Unless otherwise stated all content is protected by copyright and in the absence of an open licence (eg Creative Commons), permissions for further reuse of content should be sought from the publisher, author or other copyright holder. Versions of research The version in the Kent Academic Repository may differ from the final published version. Users are advised to check http://kar.kent.ac.uk for the status of the paper. Users should always cite the published version of record. Enquiries For any further enquiries regarding the licence status of this document, please contact: [email protected] If you believe this document infringes copyright then please contact the KAR admin team with the take-down information provided at http://kar.kent.ac.uk/contact.html JBC Papers in Press. Published on April 2, 2020 as Manuscript REV120.006194 The latest version is at https://www.jbc.org/cgi/doi/10.1074/jbc.REV120.006194 Biosynthesis of the modified tetrapyrroles—the pigments of life Donald A. Bryant1,2*, C. Neil Hunter3,‡, and Martin J. Warren4,5,§ 1Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802 2Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717 3Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom 4School of Biosciences, University of Kent, Canterbury, CT2 7NJ, United Kingdom Downloaded from 5Quadram Institute Bioscience, Norwich Research Park, Norwich NR4 7UQ, United Kingdom. http://www.jbc.org/ *Corresponding author: Donald A. Bryant E-mail: [email protected] by guest on April 14, 2020 ‡Corresponding author: C. Neil Hunter E-mail: [email protected] §Corresponding author: Martin J. Warren E-mail: [email protected] Running Title: Biosynthesis of modified tetrapyrroles Key Words: heme; chlorophyll, bilin; vitamin B12; cobalamin, coenzyme F430; heme d1; biosynthesis; tetrapyrrole; 5-aminolevulinic acid; uroporphyrinogen III; precorrin. 1 Abstract dubbed the “pigments of life” (1). These life pigments include the hemes, Modified tetrapyrroles are large chlorophylls (Chls), bilins, corrins (vitamin macrocyclic compounds, consisting of B12), siroheme, and coenzyme F430. They diverse conjugation and metal chelation are all made from a single, extensively systems and imparting an array of colors to branched biosynthetic pathway and are the biological structures that contain them. based on the blueprint of a common Tetrapyrroles represent some of the most biosynthetic primogenitor, complex small molecules synthesized by uroporphyrinogen III (Fig. 1). These cells and are involved in many essential different modified tetrapyrroles vary in the processes that are fundamental to life on nature of their peripheral side chains, the Earth, including photosynthesis, oxidation state of the macrocycle itself and respiration, and catalysis. These molecules the centrally chelated metal ion. Perhaps the are all derived from a common template most distinctive of all is vitamin B12, which through a series of enzyme-mediated contains a ring-contracted macrocycle and transformations that alter the oxidation state also houses upper and lower ligands in of the macrocycle, and also modify its size, order to provide the octahedral geometry to side chain composition, and the nature of coordinate the cobalt ion. Downloaded from the centrally chelated metal ion. The The differences in the structures of different modified tetrapyrroles include these molecules are reflected in diverse chlorophylls, hemes, siroheme, corrins biological functions. Some of the modified (including vitamin B12), coenzyme F430, tetrapyrroles are involved in very specific http://www.jbc.org/ heme d1 and bilins. After nearly a century processes; for example heme d is required of study, almost all of the more than 90 1 as a prosthetic group only for the cd1 nitrite different enzymes that synthesize this reductase (2), whereas others, such as family of compounds are now known, and heme, are involved in a myriad of distinct expression of reconstructed operons in biological roles, from sensing to catalysis by guest on April 14, 2020 heterologous hosts has confirmed that most (3). A brief description of the roles played pathways are complete. Aside from the by these molecules is outlined below. highly diverse nature of the chemical reactions catalyzed, an interesting aspect of Chls and the related comparative biochemistry is to see how bacteriochlorophylls (BChls) are the different enzymes and even entire pathways molecules that not only give plants their have evolved to perform alternative green pigmentation but are intricately chemical reactions to produce the same end involved in the process of photosynthesis products in the presence and absence of (4). Chls play two roles in photosynthesis: oxygen. Although there is still much to firstly, they act as antenna molecules and learn, our current understanding of harvest solar energy; and secondly, they tetrapyrrole biogenesis represents a transfer this energy to the reaction centers, remarkable biochemical milestone that is where photochemistry occurs that results in summarized in this review. the splitting of water or the production of strong reductants for carbon dioxide fixation and ATP generation. With only a Introduction few exceptions in which Zn2+ replaces Modified tetrapyrroles play essential roles Mg2+, Chls are Mg2+-containing chlorins, in a broad range of essential biological and the electronic properties of the chlorin processes. Their large macrocyclic ring allow for the efficient formation of a structures and diverse conjugation and singlet excited state upon visible light metal chelation systems also provide an absorption. In contrast to the metal ions array of colors such that they have been found in other modified tetrapyrroles, Mg2+ 2 is not redox active and the metal does not homolytic cleavage of the Co-adenosyl play a direct role in the light-trapping bond. These reactions include, among many process. However, the metal does appear to others, methylmalonyl CoA mutase, help potentiate the chemistry of the chlorin ribonucleotide reductase and the diol ring to make energy transfer more efficient. dehydratases (7). Adenosylcobalamin has also recently been shown to be involved as Heme is technically an Fe-containing a light sensor in a transcription factor (8). porphyrin. It has one more double bond in Corrinoids without an upper ligand act as the macrocycle than Chls and the extra the catalytic center for reductive conjugation helps produce the red colour dehalogenases, in which the cobalt ion is associated with the molecule. The central thought to form a direct bond with the Fe ion is crucial to the functions for which halide component of the substrate in order heme is used (5). Iron exists in several to mediate its abstraction (9). Finally, both oxidation states and, for this reason, heme methylcorrinoids and adenosylcorrinoids has evolved a broad range of roles within also appear to be involved in a specific biological systems, from acting as a one- group of radical SAM enzymes (6); B electron carrier in respiratory cytochromes 12- to a sensing role for a range of diatomic radical SAM enzymes are the largest group within this broad enzyme class (10). Downloaded from gases including CO, NO and O2. Heme also acts as the prosthetic group in a range of Coenzyme F430 is a nickel-containing enzymes including catalases, peroxidases tetrahydroporphyrinogen and acts as a and cytochromes P450, and is known to be coenzyme in both forward and reverse associated with certain transporters and methanogenesis (11). As a coenzyme http://www.jbc.org/ transcription factors (3). within coenzyme M reductase, the central nickel ion is able to mediate the reversible The corrinoids, sometimes also reduction/oxidation of a methyl group to referred to as cobamides, encompass produce methane in both the processes of cofactors and coenzymes that harbor by guest on April 14, 2020 methanogenesis and anaerobic methane cobalt-containing, ring-contracted corrin oxidation. In some respects, the binding of macrocycles. In biologically active nickel in coenzyme F corrinoids the cobalt atom is covalently 430 mirrors the binding linked to either a methyl or adenosyl group of cobalt in corrins, reflecting similarities in on the upper face of the macrocycle. The their respective catalytic activities in corrin ring is also attached to a lower forming metal-carbon bonds. However, in nucleotide loop via one of its propionate coenzyme F430, nickel promotes methyl side chains. The nature of the base in this group reduction, whilst in corrinoid- nucleotide loop varies among bacteria, and dependent methyltransferases the cobalt over 20 different bases are known to be promotes methyl group transfer (12). incorporated into corrinoids. The base is Demonstrating the importance of these specifically dimethylbenzimidazole in tetrapyrrole catalysts, the process of methanogenesis is responsible for the vitamin B