Catabolic pathways for arginine and methylated arginines by plant and mammalian copper amine oxidases

The oxidation of L-arginine, monomethyl L-arginine and asymmetric dimethyl arginine catalyzed by copper/TPQ-amine oxidases from lentil (Lens esculenta) seedlings and pig kidney was investigated by optical spectroscopy and HPLC analyses. L-Arginine and its methylated derivatives were shown to be poor substrates for both enzymes and were oxidized by an unusual mechanism yielding glutamate-5-semialdehyde, ammonia, urea and their derivatives as reaction products. These findings suggest that amine oxidases might represent an alternative metabolic pathway of the arginine and its methylated derivatives, yielding new metabolites like urea, methylurea and dimethylurea.