Samach A, Hareven D, Gutfinger T, Ken-Dror S, Lifschitz E
Technion, Israel Institute of Technology, Department of Biology, Haifa.
Proc Natl Acad Sci U S A. 1991 Apr 1;88(7):2678-82. doi: 10.1073/pnas.88.7.2678.
The gene encoding the plant biosynthetic threonine deaminase (Td; EC 4.2.1.16) has been cloned as a result of its unusual upregulation in tomato flowers. The Td gene of tomato encodes a polypeptide of 595 residues, the first 80 of which comprise a putative two-domain transit peptide cleaved at position 51. Comparison of the amino acid sequence with the corresponding enzymes from yeast and bacteria reveals a near identity of the important catalytic regions and greater than 40% overall similarity. The Td gene is unique in the tomato genome and its coding region is interrupted by eight introns. Its expression is greater than 50-fold higher in sepals and greater than 500-fold higher in the rest of the flower than in leaves or roots. Its overexpression, however, is strictly confined to the parenchymal cells of the floral organs. In young tomato leaves, the chloroplast-bound enzyme is found almost exclusively in the subepidermal spongy mesophyll cells.
由于其在番茄花中异常上调，编码植物生物合成苏氨酸脱氨酶（Td；EC 4.2.1.16）的基因已被克隆。番茄的Td基因编码一个由595个残基组成的多肽，其中前80个残基构成一个假定的双结构域转运肽，在第51位被切割。将该氨基酸序列与来自酵母和细菌的相应酶进行比较，发现重要催化区域几乎完全相同，总体相似度超过40%。Td基因在番茄基因组中是独特的，其编码区被8个内含子打断。它在萼片中的表达比在叶子或根中高50倍以上，在花的其他部分比在叶子或根中高500倍以上。然而，其过表达严格局限于花器官的实质细胞。在幼嫩的番茄叶片中，与叶绿体结合的酶几乎只存在于表皮下的海绵状叶肉细胞中。
