34 糸状菌DHN-メラニンの生合成に関わるポリケタイド合成酵素(口頭発表の部)

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All fungal polyketide synthase (PKS) genes so far cloned code for iterative type I PKSs different from bacterial modular type I PKSs and type II PKSs. In order to clarify how fungal PKSs control their reactions to produce specific product compounds, we have expressed several fungal PKSs in heterologous hosts and identified their product compounds. In this study, we carried out functional analysis of two fungal PKSs involved in DHN-melanin biosynthesis. The PKS1 gene cloned from the phytopathogenic fungus Colletotrichum lagenarium was assumed to code for a 1,3,6,8-tetrahydroxynaphthalene (T4HN, 1) synthase. To identify its actual function, the PKS1 gene was expressed in a heterologous fungus Aspergillus oryzae. Production of T4HN (1) by the transformant confirmed the function of PKS1 PKS as T4HN synthase. Cell-free extract prepared from the transformant showed PKS enzyme activity to form T4HN (1). Furthermore, cell-free studies identified that malonyl-CoA serves as not only extender units but also as a starter unit of enzymatic T4HN (1) formation. Aspergillus fumigatus is an important opportunistic pathogen causing aspergillosis and its conidial melanization is a key factor in its virulence. Presence of a PKS gene (alb1) was identified in its melanin biosynthetic gene cluster. T4HN (1) was expected to be a product compound of Alb 1p PKS, but naphthopyrone YWA1 (4) was produced by the heterologous expression of alb1. Homologous complementation and heterologous co-expression studies revealed that Ayg1 protein coded in the gene cluster is involved in T4HN (1) formation with Alb1p PKS. Further cell-free studies identified that Ayg1 protein can convert YWA1 (4) to T4HN (1) possibly by hydrolytic C-C bond cleavage.
天然有機化合物討論会の論文
2000-10-01

34 糸状菌DHN-メラニンの生合成に関わるポリケタイド合成酵素(口頭発表の部)

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