Chicken Ornithine Transcarbamylase: Tissue Specific Expression.

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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.