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Workshop / Seminar

Chemistry PhD Final Defense – Bixia Zhang, Chemistry Graduate Student

Fulmer Hall
Fulmer 438
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About the event

Speaker:       Bixia Zhang, chemistry graduate student

                    Kang Group

Title:              Characterization and Redox interaction between Cytochrome P450 and Cytochrome P450 Reductase from Sorghum bicolor

Abstract:      Bioenergy sorghums (Sorghum bicolor (L.) Moench) are cultivated to produce large volumes of biomass. In the context of bioenergy production, lignin has been the focus of much attention because of the negative role it plays in the enzymatic saccharification of cell wall polysaccharides. Lignin is formed from the oxidative coupling of monolignols, which are hydroxycinnamyl alcohols and related compounds synthesized from 4-coumaroyl-CoA via a series of enzymatic reactions. The detailed mechanical understanding of the monolignol pathway will enable the manipulation of lignin content in biofuel plants, and further benefits biofuel production. Much progress has been made in the understanding of lignin biosynthesis through detailed studies of the enzymes involved in the biosynthesis of monolignols, while the crucial hydroxylation steps are poorly understood. The hydroxylation steps in the monolignol pathway are achieved by cytochrome P450s, including p-coumaroyl shikimate 3′-hydroxylase (C3’H), cinnamate-4-hydroxylase (C4H), and ferulate-5-hydroxylase (F5H). These three enzymes belong to the class II P450 superfamily, where the electrons necessary for the corresponding catalysis are provided by NADPH-dependent cytochrome P450 reductase (CPR), a flavoprotein co-localized with P450 on the exterior surface of the membrane of endoplasmic reticulum (ER). This study investigated the structural and functional characteristics of p-coumaroyl shikimate 3′-hydroxylase (C3’H), cinnamate-4-hydroxylase (C4H) and cytochrome P450 reductases from sorghum, as well as the redox interaction between the P450s and CPRs. The results provide valuable information of the substrate specificity and protein-protein interaction of those key enzymes in the monolignol pathway, thus contribute to the fundamental knowledge to tune the chemical composition in the secondary cell walls of plants.