Involved in the biosynthesis of phaseolotoxin, a nonhost-specific toxin which is a key component in the development of the halo blight disease of beans (PubMed:11310742). Catalyzes the transfer of an amidino group from arginine to lysine to produce one molecule of homoarginine and one molecule of ornithine, both being precursors in the biosynthesis of phaseolotoxin (PubMed:11310742, PubMed:27419063). Can also use L-canavanine as an alternative amidine donor with L-ornithine as amidine acceptor (PubMed:27419063). L-arginine + L-lysine = L-homoarginine + L-ornithine L-canavanine + L-ornithine = H(+) + L-arginine + L-canaline Mutant loses the ability to synthesize homoarginine and phaseolotoxin under permissive conditions. Belongs to the amidinotransferase family.