Unleashing the Synthetic Power of Plant Oxygenases: From Mechanism to Application

Abstract

ORCID IDs: 0000-0003-3726-6569 (A.J.M.); 0000-0003-3059-0075 (J.-K.W.).Plant-specialized metabolites account for arguably the largest and most diverse pool of natural products accessible to humans. Conferring the plants' selective traits, such as UV defense, pathogen resistance, and enhanced nutrient uptake, these chemicals are crucial to a species' viability. During biosynthesis of these compounds, a vast array of specialized enzymes catalyze diverse chemical modifications, with oxidation being one of the most predominant (Smanski et al., 2016;Dong et al., 2018). Considering these observations, it is not surprising that within plant genomes, two families of oxygenases are the most abundant: the cytochrome P450 monooxygenases (P450s) and the iron/2-oxoglutaratedependent oxygenases (Fe/2OGs). These and other oxygenases represent the synthetic workhorses of plantspecialized metabolism and also play key roles in primary metabolism, cellular regulation, and fitness. Furthermore, the challenging and selective chemistry they catalyze cannot currently be matched by synthetic chemists. Since many plant natural products serve as valuable pharmaceuticals and commodity chemicals, plant oxygenases represent a promising toolset for synthetic biologists to manipulate plant traits or develop biocatalysts (Harvey et al., 2015). Here, we review families of plant oxygenases and their chemistry and suggest potential applications.• Oxygenases can be used as a means to manipulate many facets of plant physiology. Alfieri A, Malito E, Orru R, Fraaije MW, Mattevi A (2008) Revealing the moonlighting role of NADP in the structure of a flavin-containing monooxygenase. Proc Natl Acad Sci USA 105: 6572-6577 Arnold FH (2018) Directed evolution: Bringing new chemistry to life.

The “Green” FMOs: Diversity, Functionality and Application of Plant Flavoproteins

“…Interestingly, plants possess a higher number of monooxygenases compared to species in other kingdoms, and are especially diversified regarding major classes of CYPs [24] and the iron/2-oxoglutaratedependent oxygenases (Fe/2OGs) [6]; with several hundred CYP and Fe/2OG enzymes encoded by genes within a single plant genome. Whilst not as numerous as other monooxygenase classes, FMOs are also highly diversified compared to the number of FMOs present within other kingdoms.…”

“…The oxidation of these molecules, sometimes with high chemo-, regio-and enantio-selectivity, alters their physical and chemical properties, such as polarity, solubility, reactivity, and susceptibility for further enzymatic modifications [1]. Accordingly, FMOs are important oxidoreductases with large potential for development as biocatalysts within the biotechnological and pharmaceutical industries [1][2][3][4][5][6]. Traditionally, other oxygenase enzymes, such as cytochromes P450 (CYPs), have received comparatively more attention for their endogenous roles in vivo [7][8][9], and in regard to the identification and development of new enzyme reactions.…”

The chloroalkaloid (−)-acutumine is biosynthesized via a Fe(II)- and 2-oxoglutarate-dependent halogenase in Menispermaceae plants

“…2ODHs were previously identified in bacteria, such as SyrB2 from syringomycin E biosynthesis in Pseudomonas syringae 18 , WelO5 from welwitindolinone biosynthesis in Hapalosiphon welwischii 26 , and recently reported amino acid halogenases from Streptomyces cattleya 20 . 2ODHs are evolutionarily derived from the 2ODDs, a large enzyme family spanning all kingdoms of life 27 . Canonical 2ODDs activate molecular oxygen using a ferrous cofactor and a 2-oxoglutarate (2OG) cosubstrate to oxidize aliphatic C-H bonds at a highly conserved iron-binding facial triad (HxD/EX n H) 28 , typically resulting in a hydroxylation outcome.…”

New frontiers: harnessing pivotal advances in microbial engineering for the biosynthesis of plant-derived terpenoids

“…CYPs, in particular, are hypothesized to be a main driving force of terpenoid diversification in plants through hydroxylation, sequential oxidations of specific positions (generating anchoring points for additional modifications by transferases), as well as catalyzing ring closure and rearrangement reactions that significantly increase terpenoid complexity [21]. Most CYPs react with a distinct carbon on the terpene backbone, reactions that are challenging for synthetic chemistry, making biosynthesis of oxidized terpenoids a preferable option for production [22]. These CYPs are generally localized to the ER of the native host in close proximity to the terpene synthase producing the substrate for the reaction [23].…”