Presence and formation of heme and occurrence of certain heme proteins in the filarial parasite Setaria digitata

There is currently renewed interest in the biological significance of heme proteins. The most common heme proteins include hemoglobin, myoglobin, cyto chromes, and redox enzymes such as catalase and peroxidase, MATERIALS AND M ETHODS Setaria digitata is a cattle filarial parasite, which is devoid of t ypical cytochrome systems. However, studies showed activities of delta Amin olevulinate synthase (ALAS), delta Aminolevulinate dehydratase (ALAD), and heme oxygenase in appreciable amounts, suggesting the presence of necessary equipment for the biosynthesis of heme, This is further confirmed by the e nd product inhibition of ALAS by heme and the observation of the death of t he parasite by succinyl acetone, an inhibitor of the biosynthesis of heme, Though typical cytochrome systems are absent, microsomal cytochrome P 450 a nd elevated levels of heme containing enzymes such as catalase and peroxida se are present in the parasite. A unique hemoglobin is also detected which shows a difference in biological functions from the host system and that of the much-studied nematode parasite Ascaris sum. (C) 1998 Academic Press.