Mori M, Matsubasa T, Amaya Y, Takiguchi M
Institute for Medical Genetics, Kumamoto University Medical School, Japan.
Prog Clin Biol Res. 1990;344:683-99.
cDNA clones for rat argininosuccinate lyase, a urea cycle enzyme, were cloned and amino acid sequence of the enzyme was predicted. The rat enzyme is 54% identical with the yeast enzyme, which is involved in arginine biosynthesis, thereby indicating that this urea cycle enzyme evolved from the arginine biosynthetic enzyme. A striking similarity (64% identity) was found between amino acid sequences of rat argininosuccinate lyase and chicken delta-crystallin, a major structural protein of the eye lens. The gene for the rat argininosuccinate lyase was cloned and its structure was determined. This gene is a single-copy gene about 14 kilobases long and is split into 16 exons. A comparison with chicken delta-crystallin genes revealed that all introns interrupt the protein-coding regions at homologous positions. This close similarity in structural organization provides strong evidence for the view that the chicken delta 1- and delta 2-crystallin genes evolved by recruitment and duplication of the preexisting argininosuccinate lyase gene and that delta 2-crystallin is probably the direct homologue of argininosuccinate lyase.
大鼠精氨琥珀酸裂解酶（一种尿素循环酶）的cDNA克隆被成功克隆，并对该酶的氨基酸序列进行了预测。大鼠的这种酶与参与精氨酸生物合成的酵母酶有54%的同源性，这表明这种尿素循环酶是由精氨酸生物合成酶进化而来的。在大鼠精氨琥珀酸裂解酶的氨基酸序列和鸡的δ-晶体蛋白（晶状体的一种主要结构蛋白）之间发现了显著的相似性（64%的同源性）。大鼠精氨琥珀酸裂解酶的基因被克隆并确定了其结构。该基因是一个单拷贝基因，长度约为14千碱基，被分割为16个外显子。与鸡的δ-晶体蛋白基因的比较显示，所有内含子都在同源位置打断了蛋白质编码区。这种结构组织上的紧密相似性为以下观点提供了有力证据：鸡的δ1-和δ2-晶体蛋白基因是通过招募和复制现有的精氨琥珀酸裂解酶基因而进化而来 的，并且δ2-晶体蛋白可能是精氨琥珀酸裂解酶的直接同源物。
