This report examines the presence of proteolytic activity detected in media collected from in vitro cultures of Giardia intestinalis, and the partial characterization by
gelatin-substrate
polyacrylamide gel electrophoresis and inhibition studies.
Gelatin-substrate
polyacrylamide gel electrophoresis revealed 6 bands with proteolytic activity, with estimated molecular weights of 36, 59, 63, 72, 103, and 175 kDa. These bands were not present in the control medium. On the other hand, G. intestinalis trophozoite lysates showed proteolytic bands at 16, 20, 66, 82, 108, and 120 kDa, thus indicating that intracellular
proteases could be different from the excretory/secretory (E/S) products. Based on inhibition studies, 2 bands of 59 and 63 kDa were inhibited by
iodoacetic acid, indicating the presence of
cysteine proteases. Partial inhibition of a band of 36 kDa was found with
EDTA, a
metal-
chelating agent, suggesting the possible presence of
metalloproteases. The presence of aspartic and
serine proteases were not detected under the assay conditions used. As G. intestinalis E/S may be involved in differentiation mechanisms of the parasite and also be responsible for the mucosal alterations that occur in
giardiasis, the characterization of these
proteases may facilitate their evaluation as targets in the
therapy of the disease.