Masamura Noriya, Ohashi Wakana, Tsuge Nobuaki, Imai Shinsuke, Ishii-Nakamura Anri, Hirota Hiroshi, Nagata Toshiyuki, Kumagai Hidehiko
Somatech Center, House Foods Corporation, Yotsukaido, Chiba, Japan.
Biosci Biotechnol Biochem. 2012;76(3):447-53. doi: 10.1271/bbb.110652.
Lachrymatory factor synthase (LFS), an enzyme essential for the synthesis of the onion lachrymatory factor (propanethial S-oxide), was identified in 2002. This was the first reported enzyme involved in the production of thioaldehyde S-oxides via an intra-molecular H(+) substitution reaction, and we therefore attempted to identify the catalytic amino acid residues of LFS as the first step in elucidating the unique catalytic reaction mechanism of this enzyme. A comparison of the LFS cDNA sequences among lachrymatory Allium plants, a deletion analysis and site-directed mutagenesis enabled us to identify two amino acids (Arg71 and Glu88) that were indispensable to the LFS activity. Homology modeling was performed for LFS/23-169 on the basis of the template structure of a pyrabactin resistance 1-like protein (PYL) which had been selected from a BLASTP search on SWISS-MODEL against LFS/23-169. We identified in the modeled structure of LFS a pocket corresponding to the ligand-binding site in PYL, and Arg71 and Glu88 were located in this pocket.
催泪因子合酶（LFS）是一种对于洋葱催泪因子（丙烷硫醛S-氧化物）的合成至关重要的酶，于2002年被鉴定出来。这是首次报道的通过分子内H(+)取代反应参与硫代醛S-氧化物生成的酶，因此我们试图鉴定LFS的催化氨基酸残基，作为阐明该酶独特催化反应机制的第一步。通过对催泪葱属植物中LFS cDNA序列的比较、缺失分析和定点诱变，我们得以鉴定出两个对LFS活性不可或缺的氨基酸（Arg71和Glu88）。基于从SWISS-MODEL上针对LFS/23-169进行的BLASTP搜索中选出的类似抗脱落酸蛋白1（PYL）的模板结构，对LFS/23-169进行了同源建模。我们在LFS的模拟结构中鉴定出一个与PYL中的配体结合位点相对应的口袋，Arg71和Glu88位于这个口袋中。
