Junk Damian J, Mourad George S
Department of Biology, Indiana University-Purdue University Fort Wayne, 2101 E. Coliseum Blvd., Fort Wayne, IN 46805-1499, USA.
J Exp Bot. 2002 Dec;53(379):2453-4. doi: 10.1093/jxb/erf112.
Isopropylmalate synthase (IPMS) is the first enzyme in the leucine biosynthetic pathway. It is the branch point in the biosynthesis of leucine and the other branched-chain amino acids. IPMS is also regulated by negative feedback inhibition by the end-product leucine. There are four highly homologous loci within the Arabidopsis thaliana genome, which contain sequences that code for IPMS. Through library screening and RT-PCR the expression patterns of three of these loci namely IMS1, IMS2, and IMS3 have been isolated and then characterized. cDNAs of IMS2 and IMS3 lacking the 5' chloroplast leader sequence were able to complement a leucine auxotroph of E. coli.
异丙基苹果酸合酶(IPMS)是亮氨酸生物合成途径中的第一个酶。它是亮氨酸和其他支链氨基酸生物合成的分支点。IPMS也受到终产物亮氨酸的负反馈抑制调节。拟南芥基因组中有四个高度同源的基因座,其中包含编码IPMS的序列。通过文库筛选和逆转录聚合酶链反应(RT-PCR),已分离并鉴定了其中三个基因座(即IMS1、IMS2和IMS3)的表达模式。缺失5'叶绿体前导序列的IMS2和IMS3的互补DNA(cDNA)能够互补大肠杆菌的亮氨酸营养缺陷型。