Yamamoto Kohji, Higashiura Akifumi, Suzuki Mamoru, Aritake Kosuke, Urade Yoshihiro, Uodome Nobuko, Nakagawa Atsushi
Kyushu University Graduate School, Fukuoka, Japan.
Biochim Biophys Acta. 2013 Jun;1830(6):3711-8. doi: 10.1016/j.bbagen.2013.02.021. Epub 2013 Mar 1.
Glutathione transferases (GSTs) are members of a major family of detoxification enzymes. Here, we report the crystal structure of a sigma-class GST of Bombyx mori, bmGSTS1, to gain insight into the mechanism catalysis.
The structure of bmGSTS1 and its complex with glutathione were determined at resolutions of 1.9Å and 1.7Å by synchrotron radiation and the molecular replacement method.
The three-dimensional structure of bmGSTS1 shows that it exists as a dimer and is similar in structure to other GSTs with respect to its secondary and tertiary structures. Although striking similarities to the structure of prostaglandin D synthase were also detected, we were surprised to find that bmGSTS1 can convert prostaglandin H2 into its E2 form. Comparison of bmGSTS1 with its glutathione complex showed that bound glutathione was localized to the glutathione-binding site (G-site). Site-directed mutagenesis of bmGSTS1 mutants indicated that amino acid residues Tyr8, Leu14, Trp39, Lys43, Gln50, Met51, Gln63, and Ser64 in the G-site contribute to catalytic activity.
We determined the tertiary structure of bmGSTS1 exhibiting prostaglandin E synthase activity.
These results are, to our knowledge, the first report of a prostaglandin synthase activity in insects.
谷胱甘肽转移酶（GSTs）是主要的解毒酶家族成员。在此，我们报道家蚕sigma类GST（bmGSTS1）的晶体结构，以深入了解其催化机制。
通过同步辐射和分子置换法，分别在1.9Å和1.7Å的分辨率下测定了bmGSTS1及其与谷胱甘肽复合物的结构。
bmGSTS1的三维结构表明它以二聚体形式存在，其二级和三级结构与其他GSTs相似。尽管也检测到与前列腺素D合酶结构有显著相似性，但我们惊讶地发现bmGSTS1能将前列腺素H2转化为其E2形式。bmGSTS1与其谷胱甘肽复合物的比较表明，结合的谷胱甘肽定位于谷胱甘肽结合位点（G位点）。bmGSTS1突变体的定点诱变表明，G位点的氨基酸残基Tyr8、Leu14、Trp39、Lys43、Gln50、Met51、Gln63和Ser64有助于催化活性。
我们确定了具有前列腺素E合酶活性的bmGSTS1的三级结构。
据我们所知，这些结果是昆虫中前列腺素合酶活性的首次报道。
