Assay of soluble guanylate cyclase activity by isocratic high-performance liquid chromatography

A HPLC method alternative to labelled or unlabelled procedures was developed for the assay of guanylate cyclase (GC) activity. The substrate (GTP) and the product (cGMP) of the enzymatic reaction were separated in the isocratic mode on a μBondapak C₁₈ column. The activity of GC was linearly dependent on the amount of cGMP produced in the presence of sodium nitroprusside. This approach was applied to follow the purification of GC from bovine lung and to evaluate its stability in different storage conditions.