Chalcone synthase superfamily of type III polyketide synthases from rhubarb (Rheum palmatum)
Chalcone synthase superfamily of type III polyketide synthases from rhubarb (Rheum palmatum)
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DOI：
10.2183/pjab.81.434
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发表时间：
2005-12-01
影响因子：
3.1
通讯作者：
Noguchi, H
中科院分区：
文献类型：
--
作者：
Abe, I;Watanabe, T;Noguchi, H
查尔酮合酶（Chalcone synthase，CHS）是一类植物特异性的III型聚酮合酶（polyketide synthase，PKS），催化4-香豆酰辅酶A（4-coumaroyl-CoA）与3分子丙二酰辅酶A（malonyl-CoA）缩合生成柚皮素查尔酮（naringenin chalcone）。首次从富含芳香聚酮化合物的药用植物大黄（Rheumpalmatum）中克隆了两个新的CHS基因。重组CHS 1和CHS 2具有90%的氨基酸序列同一性，对4-香豆酰辅酶A的K-M = 61.1 μ M，k（cat）= 1.12 min（-1），K-M = 36.1 μ M，k（cat）= 0.79 min（-1）。有趣的是，CHSs保守的Thr 197，活性位点腔的残基衬里，是唯一的Cys取代CHS 1和CHS 2。值得注意的是，两种酶都接受高达C-20链长的长链脂肪酰基CoA作为起始底物，以有效地产生三酮化合物和四酮化合物α-吡喃酮。
Chalcone synthase (CHS), the pivotal enzyme in the biosynthesis of flavonoids, is a plantspecific type III polyketide synthase (PKS) that catalyzes a sequential condensation of 4-coumaroyl-CoA with three molecules of malonyl-CoA to produce naringenin chalcone. Two novel CHSs were for the first time cloned and sequenced from rhubarb (Rheum palmatum), a medicinal plant rich in aromatic polyketides. Recombinant CHS1 and CHS2, sharing 90% amino acid sequence identity, showed K-M = 61.1 mu M, k(cat) = 1.12 min(-1), and K-M = 36.1 mu M, k(cat) = 0.79 min(-1) for 4-coumaroyl-CoA, respectively. Interestingly, CHSs conserved Thr197, the residue lining the active-site cavity, is uniquely replaced with Cys in CHS1 and CHS2. It was remarkable that both enzymes accepted long-chain fatty acyl CoAs up to the C-20 chain length as a starter substrate to efficiently produce triketide and tetraketide alpha-pyrones.