Specifically catalyzes the decarboxylation of L-arginine to agmatine. Is also able to decarboxylate L-canavanine, although less efficiently. Has no S-adenosylmethionine decarboxylase (AdoMetDC) activity. H(+) + L-arginine = agmatine + CO2 Binds 1 pyruvoyl group covalently per subunit. Highly competitively inhibited by L-argininamide and L-arginine methyl ester. Also inhibited by alpha-difluoromethylarginine. Is not stimulated by potassium chloride as observed for other decarboxylases. Optimum pH is 6. Optimum temperature is 80 degrees Celsius. Highly thermostable. Retains 80% activity after incubation at 90 degrees Celsius for 10 minutes. Amine and polyamine biosynthesis; agmatine biosynthesis; agmatine from L-arginine: step 1/1. Heterooctamer of four alpha and four beta chains arranged as a tetramer of alpha/beta heterodimers. Is synthesized initially as an inactive proenzyme. Formation of the active enzyme involves a self-maturation process in which the active site pyruvoyl group is generated from an internal serine residue via an autocatalytic post-translational modification. Two non-identical subunits are generated from the proenzyme in this reaction, and the pyruvate is formed at the N-terminus of the alpha chain, which is derived from the carboxyl end of the proenzyme. The post-translation cleavage follows an unusual pathway, termed non-hydrolytic serinolysis, in which the side chain hydroxyl group of the serine supplies its oxygen atom to form the C-terminus of the beta chain, while the remainder of the serine residue undergoes an oxidative deamination to produce ammonia and the pyruvoyl group blocking the N-terminus of the alpha chain. Pyruvoyl group-containing alpha subunit. A chimeric protein containing the beta subunit of SSO0536 and the alpha subunit of SSO0585 (SpeH) has ArgDC activity and no AdoMetDC activity, implicating residues responsible for substrate specificity in the beta subunit. But additional factors in the alpha subunit are required for efficient cleavage and turnover. Belongs to the prokaryotic AdoMetDC family. Type 1 subfamily.