Biosynthesis of the fungal metabolite, piliformic acid (2-hexylidene-3-methylsuccinic acid)
作者:Nicola C. J. E. Chesters、David O'Hagan
DOI:10.1039/a606589i
日期:——
The biosynthesis of piliformic acid, a secondary
metabolite of various xylariaceous fungi, has been studied in
Poronia piliformis and Xylaria mali. The
metabolite can be retro-biosynthetically cleaved to generate a
C8 and a C3 moiety. The study reveals that
the C8 unit is derived directly from octanoate and
that the octanoate in turn originates from a fatty acid synthase
(FAS) rather than from a polyketide synthase (PKS). This
conclusion is drawn after assaying the stereochemical course of
the enoyl reductase involved in the synthesis of the octanoate
unit. The C3 unit is efficiently labelled by succinate
and the citric acid cycle intermediate oxaloacetate is implicated
as a key biosynthetic precursor. The location of deuterium after
isotopic labelling with sodium
[2H15]octanoate reveals a 1,3-hydrogen
shift, indicative of a double-bond isomerisation, operating at
a late stage in the biosynthesis. A hypothesis for piliformic
acid biosynthesis is presented and discussed in the context of
structurally related fungal and lichen metabolites.
研究了 Poronia piliformis 和 Xylaria mali 中多种木犀属真菌的次级代谢产物--木犀酸的生物合成。这种代谢物可以通过逆生物合成裂解生成一个 C8 和一个 C3 分子。研究发现,C8 单元直接来自辛酸盐,而辛酸盐又来自脂肪酸合成酶(FAS)而非聚酮苷合成酶(PKS)。这一结论是在测定了参与辛酸单元合成的烯酰还原酶的立体化学过程后得出的。C3 单元被琥珀酸有效标记,柠檬酸循环中间体草酰乙酸被认为是关键的生物合成前体。用[2H15]辛酸钠进行同位素标记后,氘的位置发生了 1,3-氢转移,表明在生物合成后期发生了双键异构化。本文提出了一种梨形酸生物合成假说,并结合结构相关的真菌和地衣代谢物进行了讨论。