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The activity of acid proteases hydrolysing haemoglobin in parasitic helminths with special reference to interspecific and intraspecific distribution

, : The activity of acid proteases hydrolysing haemoglobin in parasitic helminths with special reference to interspecific and intraspecific distribution. Parasitology 84(1): 137-147

Acid proteases hydrolyzing Hb, first described by Timms et Bueding (1959), were studied to investigate the interspecific and intraspecific distribution in adult parasitic helminths. Acid protease activity was detected in a variety of adult helminths, irrespective of their habitats, namely, parasitic nematodes, Angiostrongylus cantonensis, Dirofilaria immitis, Trichuris muris and Ascaris suum, a trematode, Paramphistomum sp. and cestodes, Diphyllobothrium erinacei and Hymenolepis nana. Much higher specific activity was observed in the blood nematodes, A. cantonensis and D. immitis than in the gastrointestinal helminths examined. The intraspecific distribution of the acid protease activity within organs was studied in those nematodes from which the organs could be anatomically separated. The highest specific activity was observed in the intestine of A. cantonensis, D. immitis and A. suum. The activity was also found in other organs such as the reproductive organs and the body wall, but to a much lesser extent. The pH optima for the hydrolysis of Hb were in the pH range 3.1-4.6. Each of the enzyme solutions from the 7 spp. of helminths hydrolyzed Hb faster than the other proteins examined but some activity on myoglobin, casein, albumin and other proteins was demonstrated. Pepstatin, a potent inhibitor of carboxyl proteases, inhibited the hydrolysis of Hb by the acid proteases of these parasites. Acid protease activity from A. cantonensis and A. suum was not inhibited in the presence of thiol-, serine- and metallo-protease inhibitors at a concentration of 10-6 M. This fact, together with the inhibitory effect of pepstatin, suggests that the enzyme activity may be due to carboxyl protease(s). Acid proteases such as cathepsin D and pepsin were simultaneously used for comparison of some enzymological characteristics. The substrate specificity of the enzyme solutions from the helminths seemed to resemble that of cathepsin D rather than that of pepsin. The effects of pH and pepstatin on the acid protease activity of the helminths were similar to those on pepsin and cathepsin D.


PMID: 7038595

DOI: 10.1017/s0031182000051738

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