Industrial Microbiology, Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.
Appl Environ Microbiol. 2011 Oct;77(19):6926-30. doi: 10.1128/AEM.05035-11. Epub 2011 Aug 5.
We determined the enzymatic characteristics of an industrially important biocatalyst, α-ketoglutarate-dependent l-isoleucine dioxygenase (IDO), which was found to be the enzyme responsible for the generation of (2S,3R,4S)-4-hydroxyisoleucine in Bacillus thuringiensis 2e2. Depending on the amino acid used as the substrate, IDO catalyzed three different types of oxidation reactions: hydroxylation, dehydrogenation, and sulfoxidation. IDO stereoselectively hydroxylated several hydrophobic aliphatic l-amino acids, as well as l-isoleucine, and produced (S)-3-hydroxy-l-allo-isoleucine, 4-hydroxy-l-leucine, (S)-4-hydroxy-l-norvaline, 4-hydroxy-l-norleucine, and 5-hydroxy-l-norleucine. The IDO reaction product of l-isoleucine, (2S,3R,4S)-4-hydroxyisoleucine, was again reacted with IDO and dehydrogenated into (2S,3R)-2-amino-3-methyl-4-ketopentanoate, which is also a metabolite found in B. thuringiensis 2e2. Interestingly, IDO catalyzed the sulfoxidation of some sulfur-containing l-amino acids and generated l-methionine sulfoxide and l-ethionine sulfoxide. Consequently, the effective production of various modified amino acids would be possible using IDO as the biocatalyst.
我们确定了一种工业上重要的生物催化剂——α-酮戊二酸依赖性 l-异亮氨酸双加氧酶（IDO）的酶学特性，该酶负责生成苏云金芽孢杆菌 2e2 中（2S，3R，4S）-4-羟基异亮氨酸。根据用作底物的氨基酸，IDO 催化了三种不同类型的氧化反应：羟化、脱氢和磺氧化。IDO 立体选择性地羟化了几种疏水性脂肪族 l-氨基酸，以及 l-异亮氨酸，并产生（S）-3-羟基-l-allo-异亮氨酸、4-羟基-l-亮氨酸、（S）-4-羟基-l-正缬氨酸、4-羟基-l-正亮氨酸和 5-羟基-l-正亮氨酸。l-异亮氨酸的 IDO 反应产物（2S，3R，4S）-4-羟基异亮氨酸，再次与 IDO 反应并脱氢生成（2S，3R）-2-氨基-3-甲基-4-酮戊酸，这也是苏云金芽孢杆菌 2e2 中发现的一种代谢物。有趣的是，IDO 催化一些含硫 l-氨基酸的磺氧化，并生成 l-蛋氨酸亚砜和 l-乙硫氨酸亚砜。因此，使用 IDO 作为生物催化剂可以有效地生产各种修饰的氨基酸。
