Fu Cheng-Yu, Tang Man-Cheng, Peng Chao, Li Lei, He Yan-Ling, Liu Wen, Tang Gong-Li
School of Life Science and Technology, Xi'an Jiaotong University, 28 Xianning West Road, Xi'an, Shaanxi 710049, China.
J Microbiol Biotechnol. 2009 May;19(5):439-46. doi: 10.4014/jmb.0808.484.
The biosynthesis study of antibiotics saframycin (SFM) in Streptomyces lavendulae and safracin (SAC) in Pseudomonas fluorescens demonstrated that 3-hydroxy-5-methyl-Omethyltyrosine (3h5mOmTyr), a nonproteinogenic amino acid, is the precursor of the tetrahydroisoquinoline molecular core. In the biosynthetic gene cluster of SAC/SFM, sacD/ sfmD encodes a protein with high homology to each other but no sequence similarity to other known enzymes; sacF/ sfmM2 and sacG/sfmM3 encode methyltransferases for Cmethylation and O-methylation; and sacE/sfmF encodes a small protein with significant sequence similarity to the MbtH-like proteins, which are frequently found in the biosynthetic pathways of nonribosomal peptide antibiotics and siderophores. To address their function, the biosynthetic cassette of 3h5mOmTyr was heterologously expressed in S. coelicolor and P. putida, and an in-frame deletion and complementation in trans were carried out. The results revealed that (i) SfmD catalyzes the hydroxylation of aromatic rings;(ii) sacD/sacF/sacG in the SAC gene cluster and sfmD/sfmM2/sfmM3 in the SFM cluster are sufficient for the biosynthesis of 3h5mOmTyr; and (iii) the mbtH-like gene is not required for the biosynthesis of the 3h5mOmTyr precursor.
对薰衣草链霉菌中抗生素沙弗霉素（SFM）和荧光假单胞菌中沙弗拉辛（SAC）的生物合成研究表明，非蛋白质ogenic氨基酸3-羟基-5-甲基-O-甲基酪氨酸（3h5mOmTyr）是四氢异喹啉分子核心的前体。在SAC/SFM的生物合成基因簇中，sacD/sfmD编码彼此具有高度同源性但与其他已知酶无序列相似性的蛋白质；sacF/sfmM2和sacG/sfmM3编码用于C-甲基化和O-甲基化的甲基转移酶；sacE/sfmF编码与MbtH样蛋白具有显著序列相似性的小蛋白质，这些蛋白质常见于非核糖体肽抗生素和铁载体的生物合成途径中。为了研究它们的功能，3h5mOmTyr的生物合成盒在天蓝色链霉菌和恶臭假单胞菌中进行了异源表达，并进行了框内缺失和反式互补。结果表明：（i）SfmD催化芳香环的羟基化；（ii）SAC基因簇中的sacD/sacF/sacG和SFM簇中的sfmD/sfmM2/sfmM3足以进行3h5mOmTyr的生物合成；（iii）3h5mOmTyr前体的生物合成不需要mbtH样基因。
