Molecular and Biochemical Parasitology, 12 (1984) 95-99 95 Elsevier MBP 00443 AN IRON-CONTAINING SUPEROXIDE DISMUTASE IN TRITRICHOMONAS FOETUS KARL R. KITCHENER l, STEVEN R. MESHNICK l, ALEXANDRA S. FAIRFIELD ~ and CHING C. WANG 2 ~Division of lnternational Medicine, Department of Medicine, Cornell University Medical College, New York, N Y 10021, U.S.A. and 2Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, San Francisco, CA 94143, U.S.A. (Received 22 December 1983, accepted 26 January 1984) Dialysed extracts of Tritrichomonas foetus were found to have superoxide dismutase at substantially higher levels than those found in trypanosomatids and mouse red blood cells. The activity was sensitive to inhibition by H202 but not by cyanide, suggesting that this organism has iron-containing superoxide dismutase(s). Three isozymes were seen by isoelectric focusing which appeared to be sensitive to inhibition by H202. Key words: Iron; Superoxide anion; Superoxide dismutase; Tritrichomonasfoetus INTRODUCTION Superoxide dismutase (SOD) catalyzes the dismutation of superoxide anion (02-) to hydrogen peroxide (H202). It has been found in almost every aerotolerant or- ganism. 02- is the one-electron reduction product of molecular oxygen which is formed both spontaneously and as a byproduct of numerous enzymatic reactions. SOD protects living organisms against the direct and indirect toxic effects of 02- [1]. Three different classes of SOD are known which differ in their metal content and in their sensitivities to cyanide, azide and hydrogen peroxide. Cu, Zn-containing SODs, which have been found in higher animals and plants, are inhibited by cyanide and H202. Mn-containing SODs have been found in prokaryotes, mitochondria and chloroplasts and are insensitive to cyanide and H202. Fe-containing SODs have been found in prokaryotes, plants and protozoa and are inhibited by H202 but not by cyanide [1,2]. Fe-containing SODs are also more sensitive to inhibition by azide than are Cu, Zn- and Mn-containing SODs [3]. We have been studying SODs from parasitic protozoa with the aim of using them as Abbreviations: Bis-C6-DHB, Na, N~-bis (2,3-dihydroxybenzoyl)-1,6-diaminohexane; SOD, superoxide dis- mutase. 0166-6851/84/$03.00 © 1984 Elsevier Science Publishers B.V.