Adenylyl cyclase Rv2212 fromMycobacterium tuberculosishas a domain composition identical to the pH-sensing isoform Rv1264, an N-terminal regulatory domain and a C-terminal catalytic domain. The maximal velo-city of Rv2212 was the highest of all 10 mycobacterial cyclases investigated to date ( cAMPÆmg )1 Æmin )1 ), whereas ATP substrate affinity was low (SC50¼ mmATP).