Hydrolyzes N(G),N(G)-dimethyl-L-arginine (ADMA) and N(G)-monomethyl-L-arginine (MMA) which act as inhibitors of NOS. Has therefore a role in the regulation of nitric oxide generation. H2O + N(omega),N(omega)-dimethyl-L-arginine = dimethylamine + L-citrulline Inhibited by zinc ions (By similarity). Enzyme purified in the absence of 1,10-phenanthroline contains on average 0.4 zinc atoms per subunit. Inhibited by 4-hydroxy-nonenal through the formation of a covalent adduct with His-173. Competitively inhibited by N(5)-iminopropyl-ornithine. Optimum pH is 8.5. Monomer. Detected in brain, liver, kidney and pancreas, and at low levels in skeletal muscle. Belongs to the DDAH family.