Investigation on the characteristic pattern of enzymes in various organisms may be of particular importance, as this type of information can help to understand certain physiological and biochemical processes in living organisms. Thiosulfate: cyanide sulfurtransferase (rhodanese) is a ubiquitous multifunctional enzyme, which its major function is generally believed to be in cyanide detoxification. The present study was conducted to determine the activity of this enzyme in some parasitic helminths including, cestodes (Moniezia benedeni, Helicometra giardi), trematodes (Fasciola hepatica, Fasciola gigantica, Dicrocoelium dendriticum) and nematodes (Haemonchus longistipes, Marshalagia marshalli). The data resultant from this study indicates that at least some rhodanese activity was present in all the seven investigated parasites, although its activity was much lower in comparison with previously reported values for some tissues of their vertebrate hosts. With respect to some degrees of cyanide insensitivity in parasitic helminths, it may be suggested that cyanide detoxification may not be a primary benefit of rhodanese in parasitic helminths and the true physiological and biochemical functions of the enzyme remains to be further defined in such organisms.

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