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Formation of two methylenedioxy bridges by a Sesamum CYP81Q protein yielding a furofuran lignan, (+)-sesamin.

ABSTRACT: (+)-Sesamin, a furofuran class lignan, is widespread in vascular plants and represented by Sesamum spp. (+)-Sesamin has been of rapidly growing interest because of its beneficial biological effects in mammals, but its biosynthesis and physiological roles in plants remain to be clarified. It is speculated to be synthesized from (+)-pinoresinol by means of (+)-piperitol by formation of two methylenedioxy bridges mediated by two distinct Sesamum indicum cytochrome P450 (SiP450) proteins. Here, we report an SiP450, CYP81Q1, that alone catalyzes (+)-sesamin biosynthesis from (+)-pinoresinol by means of (+)-piperitol by forming two methylenedioxy bridges. The CYP81Q1 gene expression profile was temporally consistent with the accumulation pattern of (+)-sesamin during seed development. The CYP81Q1-GFP chimera protein was colocalized with an endoplasmic reticulum (ER)-targeting chimera protein, indicating that (+)-sesamin biosynthesis occurs on the ER cytoplasmic surface. Moreover, we isolated two CYP81Q1 homologs from other Sesamum spp. Sesamum radiatum CYP81Q2 showed dual (+)-piperitol/(+)-sesamin synthetic activity. CYP81Q2, as well as CYP81Q1, therefore, corresponds to a (+)-piperitol/(+)-sesamin synthase in lignan biosynthesis. In contrast, Sesamum alatum CYP81Q3 showed no activity, in accord with (+)-sesamin being deficient in S. alatum. Our findings not only provide insight into lignan biosynthesis but also unravel a unique mode of cytochrome P450 action.

SUBMITTER: Ono E

PROVIDER: S-EPMC1502515 | biostudies-literature | 2006 Jun

REPOSITORIES: biostudies-literature

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Formation of two methylenedioxy bridges by a Sesamum CYP81Q protein yielding a furofuran lignan, (+)-sesamin.

Ono Eiichiro E Nakai Masaaki M Fukui Yuko Y Tomimori Namino N Fukuchi-Mizutani Masako M Saito Masayuki M Satake Honoo H Tanaka Takaharu T Katsuta Masumi M Umezawa Toshiaki T Tanaka Yoshikazu Y

Proceedings of the National Academy of Sciences of the United States of America 20060619 26

(+)-Sesamin, a furofuran class lignan, is widespread in vascular plants and represented by Sesamum spp. (+)-Sesamin has been of rapidly growing interest because of its beneficial biological effects in mammals, but its biosynthesis and physiological roles in plants remain to be clarified. It is speculated to be synthesized from (+)-pinoresinol by means of (+)-piperitol by formation of two methylenedioxy bridges mediated by two distinct Sesamum indicum cytochrome P450 (SiP450) proteins. Here, we r ...[more]

PMID: 16785429

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Project description:Sesamin (SSM) and sesamolin (SesA) are the two major furofuran lignans of sesame oil and they have been previously noticed to exert various biological actions. However, their modulatory actions on different types of ionic currents in electrically excitable cells remain largely unresolved. The present experiments were undertaken to explore the possible perturbations of SSM and SesA on different types of ionic currents, e.g., voltage-gated Na+ currents (INa), erg-mediated K+ currents (IK(erg)), M-type K+ currents (IK(M)), delayed-rectifier K+ currents (IK(DR)) and hyperpolarization-activated cation currents (Ih) identified from pituitary tumor (GH3) cells. The exposure to SSM or SesA depressed the transient and late components of INa with different potencies. The IC50 value of SSM needed to lessen the peak or sustained INa was calculated to be 7.2 or 0.6 μM, while that of SesA was 9.8 or 2.5 μM, respectively. The dissociation constant of SSM-perturbed inhibition on INa, based on the first-order reaction scheme, was measured to be 0.93 μM, a value very similar to the IC50 for its depressant action on sustained INa. The addition of SSM was also effective at suppressing the amplitude of resurgent INa. The addition of SSM could concentration-dependently inhibit the IK(M) amplitude with an IC50 value of 4.8 μM. SSM at a concentration of 30 μM could suppress the amplitude of IK(erg), while at 10 μM, it mildly decreased the IK(DR) amplitude. However, the addition of neither SSM (10 μM) nor SesA (10 μM) altered the amplitude or kinetics of Ih in response to long-lasting hyperpolarization. Additionally, in this study, a modified Markovian model designed for SCN8A-encoded (or NaV1.6) channels was implemented to evaluate the plausible modifications of SSM on the gating kinetics of NaV channels. The model demonstrated herein was well suited to predict that the SSM-mediated decrease in peak INa, followed by increased current inactivation, which could largely account for its favorable decrease in the probability of the open-blocked over open state of NaV channels. Collectively, our study provides evidence that highlights the notion that SSM or SesA could block multiple ion currents, such as INa and IK(M), and suggests that these actions are potentially important and may participate in the functional activities of various electrically excitable cells in vivo.

Dataset Information

Formation of two methylenedioxy bridges by a Sesamum CYP81Q protein yielding a furofuran lignan, (+)-sesamin.

Publications

Formation of two methylenedioxy bridges by a Sesamum CYP81Q protein yielding a furofuran lignan, (+)-sesamin.

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