L-Arginine identified as an endogenous activator for soluble guanylate cyclase from neuroblastoma cells

Guanylate cyclase in neuroblastoma N1E 115 cells was readily solubilized upon homogenization of the cells with hypotonic buffer. When the supernatant was passed through cation exchangers such as a Chelex 100 Na+ column, the guanylate cyclase activity in the effluent fraction decreased to 4-6% of the original supernatant. The addition of the acid extract of neuroblastoma cells or rat tissues to the effluent restored guanylate cyclase activity, indicating that the supernatant of neuroblastoma cells contained an acid-soluble endogenous activator for guanylate cyclase which was adsorbed on cation exchangers. The activator was purified from rat brain and identified as L-arginine by 13C- and 1H-NMR spectroscopy and paper partition chromatography. L-Arginine, at a concentration of 1-2 x 10(-5) M, stimulated guanylate cyclase activity in the effluent fraction 15-25-fold, whereas D-arginine and other basic L-amino acids were ineffective. Peptides that contained L-arginine at the NH2- or COOH-terminal also resulted in an activation of guanylate cyclase to the extent similar to that of L-arginine, while peptides that contained L-arginine inside the peptide chain failed to stimulate the activity. The activation of L-arginine seemed to operate by a mechanism similar to that induced by nitroso compounds.