HEME METABOLISM IN PROMASTIGOTES OF LEISHMANIA-DONOVANI

Promastigotes of Leishmania donovani (Dd-8 strain) showed presence of important key enzymes of heme synthesizing (delta-aminolevulinic acid synthase and ferrochelatase) and degrading theme oxygenase and biliver din reductase) systems, classical leishmanicidal drugs viz allopurinol , amphotericin B, pentamidine and CDRI compound 93/202 inhibited the h eme oxygenase activity of the parasite, whereas, 6-aminolevulinic acid synthase activity practically remained unaffected. The K-m, V-max and pH values of heme oxygenase of promastigotes were found to be 1666 mu M hemin, 625 nmol of bilirubin formed h(-1) mg protein(-1) and 7.5 re spectively. The findings suggest the presence and importance of heme m etabolism in the de novo synthesis of different hemoproteins of the Le ishmania parasite as well as the detoxification and its defence agains t biological insults.