Comparative Analysis And Parasitic Adaptation Studies Of The Flat Animal Degradation Group

Proteases distribute widely in organisms,the degradome is the complete set of proteases that are expressed at a specific moment or circumstance by a cell,tissue or organism.Their catalytic function is to hydrolyze peptide bonds,and they have many important physiological functions.Comparative genomic analysis of degradomes between different categories may help us to understand their function.There are three categories of organisms in Platyhelminthes,including the free-living planaria and the parasitic trem atode and tapeworm.Although the trematode and tapeworm are both helminths,but their living environments and feeding ways are obviously different.The differences may result in the degradomes producing some corresponding biological characteristics,especially in parasites.We retrieved and culled the redundant protease sequences of Schmidtea mediterranea,Schistosoma japonicum,Schistosoma mansoni,Clonorchis sinensis,Echinococcus granulosus,Echinococcus multilocularis and Hymenolepis microstoma public databases utilizing bioinformatic approaches.We compared the proteases among different platyhelminthes for researching their diversity and respective traits.Then a further research with emphasis on Schistosome proteases for adaptive evolution was done.The followings were concluded:We firstly perform homologous search on genomes of several platyhelminthes,got seven degradomes.Then multiple comparisons of the functions of their specific proteases among three categories of platyhelminthes was performed.The results of the comparison among planaria,trematode and tapeworm show that planaria have the most proteases,and those proteases have more functions and join more biological processes.Trematode and tapeworm possess of less specific proteases than planaria,their functions are approximately the same as planaria.Compare to trematode and tapeworm,the specific proteases of planaria are mainly have functions on movement,biological adhesion and so on.Those divergences are consistent with the different life styles and living environment between planaria and two parasitic worms.The free-living planaria develop better than trematode and tapeworm in locomotion,nervous system and so on,while the latter degenerate in those aspects because of autoeciousness,so planaria have more development protease system.The comparison between trematode and tapeworm found that their proteases are different in several functions,but this functions are mainly basal biological processes.The comparison between Schistosome and Clonorchis sinensis revealed similar numbers and kinds of proteases.This is related to their near evolutionary relationship and similar life styles.We also make a further analysis on proteases of Schistosome,the result revealed that Schistosome proteases have happened a series of adaptive evolution which are related to the parasitic life,mainly reflected in the digestion and invasion.In order to efficiently digest hemoglobin,involved in the digestion of cathepsin B,D developed a new enzyme subtype,and some of the enzyme subtypes have replication phenomenon,resulting in multiple copies,and select the pressure analysis found that cathepsin D was significantly selected effect.Clonorchis sinensis involved in the digestion of the aspartic protease A01 family has amplification phenomenon.Invasion of the host,the schistosomiasis produced several new enzymes:elastase and cercaria protease(S01 family),invadolysin(M08 family).Tapeworm degradome lose some proteases,genome comparison found that tapeworm loss of proteases and metabolic pathways.Tapeworms and flukes have lost some enzyme of amino acid and nucleic acid metabolism.