Chicken Ornithine Transcarbamylase: Tissue Specific Expression.

在输尿管动物中，鸟氨酸转氨基甲酰基酶（OTC） [ec .2.1.3.3]是参与尿素合成的尿素循环酶之一。这种酶位于线粒体中。对于尿毒症动物，OTC无生理学意义。然而，雏鸡肾脏的酶活性差异很大。这意味着鸡已经保守了OTC基因，并且在导致活性变化的结构基因和规则基因上积累了大量突变。作者发现OTC基因在鸡的所有器官中都有翻译，但其活性在肾脏中有限制性表达。提示除肾外，鸡各脏器均缺乏预成型OTC的加工过程；通过这个过程，前体酶转化为成熟酶，在线粒体中形成一种活性酶。在进化过程中，鸡获得了利用嘌呤核苷酸合成过程为废氮生成尿酸的新途径。同时，它们会通过改变加工过程来阻止尿素合成，并在很小的变化下保留了尿素合成的基因。

In ureoteric animals, ornithine transcarbamylase(OTC) [E.C.2.1.3.3] is one of the urea cycle enzmyes involving in the synthesis of urea. The enzyme locates in mitochondria. In uricoteric animals OTC would have no physiological meaning. How-ever, chicks show the enzyme activity in their kidney with great variation. This means that chicken have conserved the gene for OTC and have accumulated much mutations at the structural and the regularoty genes causing the variation in activity. The auther found that the gene for OTC is translated in all chicken organs, but the activity is restrictively expressed in the kidney. This suggests lack of the processing process of preform OTC in all chicken organs, but the kidney; by the process the precursor enzyme is converted to the mature one to make an active enzyme in mitochondria. During evolution, chicken acquired new pathway to produce uric acid for waste nitrogen using the process of purine nucleotides synthesis. at the same time, they would prevent urea synthesis by making change the processing process and have conserved the genes of urea synthesis with a little change.