4 植物ポリケタイド合成酵素の触媒機能の多様性と非天然型新規化合物ライブラリーの構築(口頭発表の部)

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1. The physiological function of chalcone synthase and stilbene synthase are the formation of naringenin chalcone and resveratrol, respectively. The enzymes use 4-coumaroyl-CoA, performs three condensations with malonyl-CoA, and folds the resulting tetraketide into a new aromatic ring system. We investigated the capacity to build novel and unusual polyketides from alternative substrates. Three types of products were obtained: (i) complete reaction (chlcone-or stilbene-type), (ii) three condensations without formation of aromatic ring (CTAL-type pyrone derailment), (iii) two condensations (BNY-type pyrone derailment). For both enzymes, all product types were obtained from 4-fluorocinnamoyl-CoA and analogs in which the coumaroyl moiety was replaced by furan or thiophene. The results show that minor modifications can be used to direct the enzyme reaction to form a variety of different and new products. Manipulation of the biosynthesis of polyketides by synthetic analogs could lead to development of a chemical library of pharmaceutically interesting novel polyketides. 2. Benzalacetone synthase (BSA) is a novel plant-specific polyketide synthase that catalyzes a one step decarboxylative condensation of 4-coumaroyl-CoA with malonyl-CoA. A cDNA encoding BAS was for the first time cloned and sequenced from Rheum palmatum, a medicinal plant rich in pharmaceutically important phenylbutanone glucosides. The cDNA encoded a 42 kDa protein that shares 60-75% amino acid sequence identity with other members of the CHS-superfamily enzymes. Interestingly, R. palmatum BAS lacks the active-site Phe215 residue (numbering in CHS) which has been proposed to help orient substrates and intermediates during the sequential condensation of 4-coumaroyl-CoA with malonyl-CoA in CHS.
天然有機化合物討論会の論文
2001-09-01

4 植物ポリケタイド合成酵素の触媒機能の多様性と非天然型新規化合物ライブラリーの構築(口頭発表の部)

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