A recently discovered 3,5-dihydro-5-methylidene-4H-imidazol-4-one (MIO)-dependent tyrosine aminomutase (OsTAM) from rice [Yan, J., et al. (2015) Plant Cell 27, 1265] converts (S)-α-tyrosine to a mixture of (R)- and (S)-β-tyrosines, with high (94%) enantiomeric excess, which does not change with pH, like it does for two bacterial TAMs. The KM of 490 μM and the kcat of 0.005 s–1 are similar for other TAM enzymes. OsTAM is unique and also catalyzes (R)-β- from (S)-α-phenylalanine. OsTAM principally retains the configuration at the reactive Cα and Cβ centers during catalysis much like the phenylalanine aminomutase on the Taxol biosynthetic pathway in Taxus plants.
最近发现的一种来自
水稻的3,
5-二氢-5-亚甲基-
4H-咪唑-4-酮(MIO)依赖性
酪氨酸氨基变构酶(OsTAM)[Yan, J., et al. (2015) Plant Cell 27, 1265]可将(S)-α-
酪氨酸转化为(R)-和(S)-β-
酪氨酸的混合物,对映体过量率高(94%),不会像两种细菌TAM那样随pH值变化。其 KM 为 490 μM,kcat 为 0.005 s-1,与其他 TAM 酶相似。OsTAM 是独特的,它也能催化 (S)-α- 苯丙
氨酸生成 (R)-β-。OsTAM 在催化过程中主要保留了反应性 Cα 和 Cβ 中心的构型,这与 TAxus 植物中 TAxol
生物合成途径上的苯丙
氨酸
氨基变构酶非常相似。