Cytochromes P450 in the biosynthesis of glucosinolates and indole alkaloids

Abstract

Characteristic of cruciferous plants is the synthesis of nitrogen-and sulfur-rich compounds, such as glucosinolates and indole alkaloids. The intact glucosinolates have limited biological activity, but give rise to an array of bioactive breakdown products when hydrolysed by endogenous b-thioglucosidases (myrosinases) upon tissue disruption. Both glucosinolates and indole alkaloids constitute an important part of the defence of plants against herbivores and pathogens, with the difference that a basal level of glucosinolates is ever-present in the plant whereas indole alkaloids are true phytoalexins that are de novo synthesised upon pathogen attack. With the completion of the genome sequence of the model plant, Arabidopsis thaliana, which is a crucifer, many genes involved in the biosynthesis of glucosinolates and indole alkaloids have been identified and cytochromes P450 are key players in these pathways. In the present review, we will focus on the cytochromes P450 in the biosynthesis of both groups of compounds. Their functional roles and regulation will be discussed.

Arabidopsis cytochrome P450s through the looking glass: a window on plant biochemistry

“…Two of those in the chloroP list, CYP79B2 and CYP79B3 involved in the synthesis of glucosinolates that are thought to be chloroplast-localized (described further in Nafisi et al (2006) in this volume) display activities when expressed in E. coli and reconstituted with purified sorghum or rat microsomal P450 reductases (Hull and Celenza 2000;Mikkelsen et al 2000). Others predicted by chloroP to be chloroplast-localized, such as CYP707A1 and CYP707A3 mediating ABA degradation (Kushiro et al 2004;Saito et al 2004), have been expressed in yeast and insect cells in the presence of the ER-localized Arabidopsis P450 reductase and are likely to be ER-localized.…”

HPLC method validation for measurement of sulforaphane level in broccoli by‐products

“…This isothiocyanate is derived from a family of compounds called glucosinolates, which are relatively unique to cruciferous vegetables such as broccoli, Brussels sprouts, caulifl ower and cabbage (Matusheski et al, 2001). Sulforaphane is formed from its glucosinolate (glucoraphanin) by the enzyme myrosinase (thioglucoside glucohydrolase 3.2.3.1), which is released when plant cells are damaged, as occurs during cutting or chewing (Zhang and Talalay, 1998;Nafi si et al, 2006). The sulforaphane has attracted much recent interest since it was found to be the most potent naturally occurring inducer of the detoxifi cation of potential carcinogenic substances (Zhang et al, 1992;Zhang and Callaway, 2002;Morimitsu et al, 2002).…”

Controlled indole-3-acetaldoxime production through ethanol-induced expression of CYP79B2

“…The double cyp79b2 cyp79b3 mutant (2X) correspondingly is devoid of I-GLSs (Zhao et al 2002), displays reduced amounts and synthesis rates of IAA (Zhao et al 2002;Ljung et al 2005), and is unable to mount induced production of camalexin (Glawischnig et al 2004). Metabolic blocking of the post-aldoxime steps by loss-of-function mutations in CYP83B1 and SUR1 results in high-auxin superroot phenotypes (for review see NaWsi et al 2006). Overexpression of CYP83B1 causes depletion of the IAOx pool and leads to a characteristic low-auxin phenotype .…”