The Colletotrichum lagenarium PKS1 gene was expressed in the heterologous fungal host, Aspergillus oryzae, under the starch-inducible α-amylase promoter to identify the direct product of polyketide synthase (PKS) encoded by the PKS1 gene. The main compound produced by an A. oryzae transformant was isolated and characterized to be 1,3,6,8-tetrahydroxynaphthalene (T4HN) as its tetraacetate. Since the PKS1 gene was cloned from C. lagenarium to complement the nonmelanizing albino mutant, T4HN was assumed to be an initial biosynthetic intermediate, and thus the product of the PKS reaction, but had not been isolated from the fungus. The production of T4HN by the PKS1 transformant unambiguously identified the gene to encode a PKS of pentaketide T4HN. In addition, tetraketide orsellinic acid and pentaketide isocoumarin were isolated, the latter being derived from a pentaketide monocyclic carboxylic acid, as by-products of the PKS1 PKS reaction. Production of the pentaketide carboxylic acid provided insights into the mechanism for the PKS1 polyketide synthase reaction to form T4HN.
Colletotrichum lagenarium的PKS1
基因在异源真菌宿主——米曲霉(Aspergillus oryzae)中表达,采用淀粉诱导的
α-淀粉酶启动子,以识别PKS1
基因编码的聚酮合酶(PKS)直接产物。通过分离和表征,从A. oryzae转化株中产生的主要化合物被鉴定为1,3,6,8-四羟基
萘(T4HN),其
四乙酸酯形式存在。由于PKS1
基因是从C. lagenarium中克隆出来的,用于补充非
黑色素化的白化突变体,因此T4HN被假定为初始
生物合成中间体,因此被认为是PKS反应的产物,但尚未从真菌中分离出来。PKS1转化株生产的T4HN明确识别了该
基因编码一种五聚酮T4HN的PKS。此外,还分离出了四聚酮或塞林酸和五聚酮异
香豆素,后者来源于一种五聚酮单
环羧酸,作为PKS1 PKS反应的副产物。五聚
酮羧酸的生成为PKS1聚酮合酶反应形成T4HN的机制提供了见解。