ChEBI: 8-bromo-3',5'-cyclic GMP is a 3',5'-cyclic purine nucleotide that is 3',5'-cyclic GMP bearing an additional bromo substituent at position 8 on the guanine ring. A membrane permeable cGMP analogue that activates protein kinase G (PKG). It is 4.3-fold more potent than cGMP in activating PKG1alpha and promotes relaxation of tracheal and vascular smooth muscle tissue in vitro. It has a role as a muscle relaxant and a protein kinase G agonist. It is a 3',5'-cyclic purine nucleotide and an organobromine compound. It derives from a 3',5'-cyclic GMP.