The study describes the purification and characterization of adenylate cyclase activity from Trypanosoma cruzi. Adenylate cyclase activity associated with sedimentable fractions of T. cruzi was solubilized using non-ionic detergent Lubrol PX and 0.5 M (NH4)2SO4. Hydrodynamic and molecular parameters were determined for a partially purified enzyme-detergent complex, including a sedimentation coefficient of 6.2 S, Stokes radius of 5.65 nm, partial specific volume of 0.83 ml/g, molecular weight (M_r) of 244,000, and a frictional ratio of 1.33. The detergent-free protein had an M_r of about 124,000. The pI of the enzyme was 6.2. A monoclonal antibody to T. cruzi adenylate cyclase was obtained, which inhibited cyclase activities from several lower eukaryotic organisms. The T. cruzi adenylate cyclase was further purified using this antibody in immunoaffinity chromatographic columns. SDS/polyacrylamide-gel electrophoresis showed a main polypeptide band with an apparent M_r of about 56,000, which specifically reacted with the monoclonal antibody. The enzyme system responsible for cyclic AMP synthesis in lower eukaryotic organisms may be an important tool for functional and structural studies of the catalytic entity of adenylate cyclase. Adenylate cyclase activity in T. cruzi has two interesting properties: dependency on Mn²+ and insensitivity to fluoride. The enzyme may interact with regulatory factors from avian erythrocyte membranes and may interact with calmodulin, inducing Ca²+-dependent stimulation. The study suggests that some adenylate cyclases from lower eukaryotic organisms may consist of catalytic entities similar to those found in avian or mammalian membranes, but lacking most of the regulatory factors. Immunological studies indicate that some epitopic areas in the enzyme molecule were not conserved during evolution. The present study extends previous research on Neurospora adenylate cyclase to T. cruzi adenylate cyclase, focusing on purification, characterization, and interaction with a monoclonal antibody. The enzyme was purified using immunoaffinity chromatography, and the purified enzyme showed a main polypeptide band with an apparent M_r of about 56,000. The monoclonal antibody to T. cruzi adenylate cyclase also inhibited Neurospora adenylate cyclase activity, indicating that the same epitope exists in the enzyme from these two lower eukaryotic organisms. The study highlights the importance of adenylate cyclase in lower eukaryotic organisms and its potential for functional and structural studies.The study describes the purification and characterization of adenylate cyclase activity from Trypanosoma cruzi. Adenylate cyclase activity associated with sedimentable fractions of T. cruzi was solubilized using non-ionic detergent Lubrol PX and 0.5 M (NH4)2SO4. Hydrodynamic and molecular parameters were determined for a partially purified enzyme-detergent complex, including a sedimentation coefficient of 6.2 S, Stokes radius of 5.65 nm, partial specific volume of 0.83 ml/g, molecular weight (M_r) of 244,000, and a frictional ratio of 1.33. The detergent-free protein had an M_r of about 124,000. The pI of the enzyme was 6.2. A monoclonal antibody to T. cruzi adenylate cyclase was obtained, which inhibited cyclase activities from several lower eukaryotic organisms. The T. cruzi adenylate cyclase was further purified using this antibody in immunoaffinity chromatographic columns. SDS/polyacrylamide-gel electrophoresis showed a main polypeptide band with an apparent M_r of about 56,000, which specifically reacted with the monoclonal antibody. The enzyme system responsible for cyclic AMP synthesis in lower eukaryotic organisms may be an important tool for functional and structural studies of the catalytic entity of adenylate cyclase. Adenylate cyclase activity in T. cruzi has two interesting properties: dependency on Mn²+ and insensitivity to fluoride. The enzyme may interact with regulatory factors from avian erythrocyte membranes and may interact with calmodulin, inducing Ca²+-dependent stimulation. The study suggests that some adenylate cyclases from lower eukaryotic organisms may consist of catalytic entities similar to those found in avian or mammalian membranes, but lacking most of the regulatory factors. Immunological studies indicate that some epitopic areas in the enzyme molecule were not conserved during evolution. The present study extends previous research on Neurospora adenylate cyclase to T. cruzi adenylate cyclase, focusing on purification, characterization, and interaction with a monoclonal antibody. The enzyme was purified using immunoaffinity chromatography, and the purified enzyme showed a main polypeptide band with an apparent M_r of about 56,000. The monoclonal antibody to T. cruzi adenylate cyclase also inhibited Neurospora adenylate cyclase activity, indicating that the same epitope exists in the enzyme from these two lower eukaryotic organisms. The study highlights the importance of adenylate cyclase in lower eukaryotic organisms and its potential for functional and structural studies.