Chicken Ornithine Transcarbamylase: Tissue Specific Expression.

在输尿管动物中，鸟氨酸转氨甲酰酶（OTC）[E.C.2.1.3.3]是参与尿素合成的尿素循环酶之一。该酶位于线粒体中。在尿酸血症动物中，OTC没有生理学意义。但是，雏鸡肾脏中的酶活性变化很大。这意味着鸡已经保守了OTC基因，并且在结构和调节基因上积累了许多突变，导致活性的变化。作者发现OTC基因在鸡的所有器官中都有翻译，但其活性仅在肾脏中表达。这表明，除了肾脏外，鸡的所有器官都缺乏OTC前体的加工过程;通过这个过程，前体酶转化为成熟酶，在线粒体中形成活性酶。在进化过程中，鸡获得了利用嘌呤核苷酸合成过程产生尿酸的新途径。同时，它们通过改变加工过程来阻止尿素的合成，并使尿素合成的基因保持不变。

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.