Dual factors required for cytochrome-P450-mediated hydrocarbon ring contraction in bacterial gibberellin phytohormone biosynthesis

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2023-06-20
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Nagel, Raimund
Alexander, Liza E.
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The Proceedings of the National Academy of Sciences
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Stewart, Charles
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Peters, Reuben
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Biochemistry, Biophysics and Molecular Biology

The Department of Biochemistry, Biophysics, and Molecular Biology was founded to give students an understanding of life principles through the understanding of chemical and physical principles. Among these principles are frontiers of biotechnology such as metabolic networking, the structure of hormones and proteins, genomics, and the like.

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The Department of Biochemistry and Biophysics was founded in 1959, and was administered by the College of Sciences and Humanities (later, College of Liberal Arts & Sciences). In 1979 it became co-administered by the Department of Agriculture (later, College of Agriculture and Life Sciences). In 1998 its name changed to the Department of Biochemistry, Biophysics, and Molecular Biology.

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1959–present

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  • Department of Biochemistry and Biophysics (1959–1998)

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Abstract
Cytochromes P450 (CYPs) are heme-thiolate monooxygenases that prototypically catalyze the insertion of oxygen into unactivated C–H bonds but are capable of mediating more complex reactions. One of the most remarked-upon alternative reactions occurs during biosynthesis of the gibberellin A (GA) phytohormones, involving hydrocarbon ring contraction with coupled aldehyde extrusion of ent-kaurenoic acid to form the first gibberellin intermediate. While the unusual nature of this reaction has long been noted, its mechanistic basis has remained opaque. Building on identification of the relevant CYP114 from bacterial GA biosynthesis, detailed structure–function studies are reported here, including development of in vitro assays as well as crystallographic analyses both in the absence and presence of substrate. These structures provided insight into enzymatic catalysis of this unusual reaction, as exemplified by identification of a key role for the “missing” acid from an otherwise highly conserved acid–alcohol pair of residues. Notably, the results demonstrate that ring contraction requires dual factors, both the use of a dedicated ferredoxin and absence of the otherwise conserved acidic residue, with exclusion of either limiting turnover to just the initiating and more straightforward hydroxylation. The results provide detailed insight into the enzymatic structure–function relationships underlying this fascinating reaction and support the use of a semipinacol mechanism for the unusual ring contraction reaction.
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This article is published as Nagel, Raimund, Liza E. Alexander, Charles E. Stewart Jr, and Reuben J. Peters. "Dual factors required for cytochrome-P450-mediated hydrocarbon ring contraction in bacterial gibberellin phytohormone biosynthesis." Proceedings of the National Academy of Sciences 120, no. 26 (2023): e2221549120. Posted with permission.

This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
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