Renin, a protease secreted by the kidney, plays a key role in the renin-angiotensin system. Renin acts by converting the renin substrate, angiotensinogen, to angiotensin I in the blood, where it is further converted into angiotensin II. Since an overactive renin-angiotensin system leads to hypertension, renin is an attractive target for the treatment of this disease. Recombinant rat renin, expressed as prorenin and converted to the active enzyme, can be used in FRET-based enzyme activity assays, e.g. SensoLyte® Rat Renin Assay (cat# 72140) or as a positive control for IP, and ELISA.