An active urea cycle and carbamoyl-phospahte synthetase ffl in muscle of an alkaline lake-adapted fish

Most fish are ammonotelic, but under certain circumstances some fish excrete urea as a major excretory product and have an active urea cycle. An example is the alkaline lake-adapted tilapia (Orcochromis alcalicus grahami) that lives in waters at pH 10 and excretes nitrogen wastes as urea instead of ammonia. The units in liver of the glutaminc- and acetylglutamate-dependent carbamoyl-phosphate synthetase lu (CPSase HI), which catalyzes the first …