The arginase protein sequences of 15 different organisms were aligned and compared to assess their degree of similarity. The branches on the tree represent the bootstrap values. These values were calculated to determine the frequency of similarity of arginase protein sequences among the various organisms. The organisms with a greater degree of similarity have a higher bootstrap value, whereas those organisms with lesser degree of similarity have a lower bootstrap value. The sequences were also compared using a weblogo that consists of a series of stacks, one stack for each position in the sequence. A greater amount of amino acid sequence conservation is represented by taller stacks, while a lesser amount of amino acid sequence conservation is represented by smaller stacks. The height of the symbol within the stack indicates the relative frequency of each amino acid at that particular position. In addition to using computer programs, extensive research was conduction on the structure and function of both isoforms of arginase (ARG I and ARG II) and their metabolic roles in the urea cycle, as well as in ammonotelic and uricotelic organisms. 

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The results from the phylogenetic tree display high bootstrap values between species previously known to be closely genetically related. A bootstrap value of 98 is displayed between the human and sooty mangabey (primate), 100 between the Japanese killifish and Japanese Pufferfish, and 99 between the Yangtze River Dolphin and North Pacific Minke Whale. Even a bootstrap value of 99 is observed linking three different avian species to the Chinese Alligator and the Chinese Softshell Turtle. Also, the presence of high stacks and tall symbols as seen in the weblogo alignment also suggest a high degree of arginase amino acid sequence similarity. The data obtained from both of these programs is consistent with our hypothesis that similar arginase amino acid sequences can be seen among many diverse species, supporting a degree of genetic relationship and possible common ancestry. 

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In the organisms that were observed, the following was found: Despite the ammonotelic nature of fish, arginase activity was found in the liver of lungfish. In marine elasmobranchs and most ammoniotelic teleosts, arginase activity was mainly mitochondrial. In some freshwater and marine fishes, cytosolic and mitochondrial arginases were found. A study was conducted that indicated the subcellular localization of different urea cycle enzymes in freshwater nonneurogenic fishes as well. In three adult teleosts and a holstein fish, arginase activity is mostly mitochondrial (84–98%) (Srivastava and Ratha, 2013). An additional study reported the presence of both cytosolic and mitochondrial in the liver of a marine toadfish (Srivastava and Ratha, 2013). The gulf toadfish, oyster toadfish, and plainf in midshipman were also observed. The gulf fish cytosolic arginase varies from 35-62% and mitochondrial arginase 29-44% of the total liver arginase activity (Srivastava and Ratha, 2013). The two arginases were reported to have similar properties. The study found that fish use arginase II in the process of alternative activation of macrophages in type II immune responses (Srivastava and Ratha, 2013). 

 

Another study was conducted on rats that focused on the effects of arginase I and arginase II (Choi et al., 2012). These effects were studied using Western blot analysis and Immunohistochemistry. ​In the various rat organs, tissues were analyzed through western blot analysis. The results showed that arginase I was high in the liver while arginase II was high in the kidneys and the pancreas (Choi et al., 2012). The results suggested that the levels of arginase I and arginase  II varied in different organs, and that each isoform plays a specific role in the urea cycle. When the organs were studied using immunohistochemistry, it was found that there is a high presence of arginase I in the liver specifically in the nuclei and cytosol and higher levels of the arginase II in the pancreas (Choi et al., 2012). It is suggested that arginase 1 is involved in detoxification. Both arginase I and arginase II were present in the organs of the digestive system. Immunohistochemical analysis showed that arginase I is present in the pancreatic islets and arginase II is present in the acini. This suggests that arginase II plays a key role with exocrine glands in the digestive system (Choi et al. 2012).