(-)-valencene (5) in a 94:4:2 ratio. By contrast, the closely related aristolochene synthase from Aspergillus terreus cyclized farnesyl diphosphate only to (+)-aristolochene (4). Site-directed mutagenesis of amino acid residues in two highly conserved Mg(2+)-binding domains led in most cases to reductions in both k(cat) and k(cat)/K(m) as well as increases in the proportion of (S)-(-)germacrene A (2)
法呢基二
磷酸 (1) 与 Penicillium roqueforti aristolochene 合酶的孵育产生 (+)-
马兜铃烯 (4),伴随着少量提议的中间体 (S)-(-)germacrene A (2) 和副产物 (-) -价 (5) 的比例为 94:4:2。相比之下,来自土曲霉的密切相关的马兜铃合成酶仅将法呢基二
磷酸环化为 (+)-马兜铃 (4)。在大多数情况下,两个高度保守的 Mg(2+) 结合域中
氨基酸残基的定点诱变导致 k(cat) 和 k(cat)/K(m) 的减少以及(S)-(-)germacrene A (2),P. roqueforti aristolochene 合酶的 E252Q 突变体仅产生 (-)-2。P. roqueforti D115N、N244L 和 S248A/E252D 突变体是无活性的,A. terreus 突变体 E227Q 也是如此。P。roqueforti