ISOLATION OF A NITRIC-OXIDE SYNTHASE FROM THE PROTOZOAN PARASITE, LEISHMANIA-DONOVANI

A soluble nitric oxide synthase (NOS) activity was purified 2800-fold from Leishmania donovani, the causative parasite of visceral leishmani asis, by two-step affinity and anion-exchange chromatography. The puri fied enzyme ran as a prominent band of 110 kDa on SDS-PAGE whereas gel filtration experiments estimated the native molecular mass to be 230/-20 kDa indicating that the native enzyme exists as a dimer. The enzy me activity required NADPH and was blocked by EGTA. The enzyme kinetic s, cofactor requirements, inhibition studies and Western blot analysis with brain anti-NOS antibody suggest its similarity with mammalian NO S isoform I.