Nara T, Gao G, Yamasaki H, Nakajima-Shimada J, Aoki T
Department of Parasitology, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo 113-8421, Japan.
Biochim Biophys Acta. 1998 Sep 8;1387(1-2):462-8. doi: 10.1016/s0167-4838(98)00127-7.
Genes for carbamoyl-phosphate synthetase II (CPS II), the first enzyme of de novo pyrimidine biosynthesis, were cloned from kinetoplastids, Trypanosoma cruzi and Leishmania mexicana. T. cruzi CPS II gene encodes a protein of 1524 amino acids that encompasses the glutaminase and CPS domains, but incorporates neither aspartate carbamoyltransferase nor dihydroorotase. The residue corresponding to lysine 993 of Escherichia coli CPS, a residue that characterizes the CPS inhibited by UMP and that is replaced by tryptophan in those inhibited by UTP, is in kinetoplastids a hydrophilic glutamine, in line with the preferential inhibition by UDP of kinetoplastid CPS II.
从头嘧啶生物合成的首个酶——氨甲酰磷酸合成酶II（CPS II）的基因，是从动基体生物克氏锥虫和墨西哥利什曼原虫中克隆出来的。克氏锥虫CPS II基因编码一个由1524个氨基酸组成的蛋白质，该蛋白质包含谷氨酰胺酶和CPS结构域，但既不包含天冬氨酸氨甲酰转移酶也不包含二氢乳清酸酶。与大肠杆菌CPS的赖氨酸993相对应的残基，该残基是UMP抑制的CPS的特征性残基，并且在UTP抑制的那些酶中被色氨酸取代，在动基体生物中是一个亲水性谷氨酰胺，这与动基体生物CPS II受UDP优先抑制一致。
