Inactive Renin — Through a Glass Darkly

Many enzymes (e.g., pepsin) and endocrine hormones (e.g., insulin) are synthesized first in the form of an inactive zymogen, which is then subject to proteolytic cleavage before eventual secretion in active form. By analogy, investigators have focused attention on inactive renin as a possible zymogen. Does inactive renin represent a precursor of renin? Does the transformation of inactive to active form represent one of the modes for regulating renin activity? The study of inactive renin has been hampered by inadequate methods. The inactive forms of renin represent an extremely small fraction of total renal or plasma proteins and are highly . . .