Transglutaminase in Plasmodium parasites: activity and putative role in oocysts and blood stages

Transglutaminase was identified in malaria parasites by immunofluorescence microscopy using alpha -transglutaminase antiserum. Functional enzyme was d emonstrated in vivo and in vitro using labeled polyamines that become incor porated into protein substrates through TGase activity. In Plasmodium falci parum intraerythrocytic parasites, transglutaminase activity was stage-depe ndent: it was weak in ring-forms but much stronger in trophozoites and schi zonts. High levels of activity were detected in P. gallinaceum zygotes and ookinetes and in capsules of oocysts developing on mosquito midguts. Unlike most known transglutaminases. the enzymatic activity in Plasmodium was Ca2 +-independent. Furthermore. levels of activity were similar at 37 and 26 de greesC Parasite transglutaminase may be responsible for the modification of erythrocytic cytoskeleton in infected cells and it may facilitate the cons truction of oocyst capsules by cross-linking mosquito-derived basement memb rane components with Plasmodium-derived proteins. (C) 2001 Elsevier Science B.V. All rights reserved.