The adenylyl cyclase activity of the fission yeast Schizosaccharomyces pombe is localized to the plasma membrane of the cell. The enzyme utilizes Mn 2 + /ATP as substrate and free Mn 2 + ions as an effector. Unlike the baker yeast Saccharomyces cerevisiae, S. pombe adenylyl cyclase does not utilize Mg 2 + /ATP as substrate and the activity is not stimulated by guanyl nucleotides. The optimal pH for the S. pombe adenylyl cyclase activity is 6.0. The activity dependence on ATP is cooperative with a Hill coefficient of 1.68 +/- 0.14.