Pepstatin inhibition of human renin. Kinetic studies and estimation of enzyme purity.

Pepstatin has been shown to be an extremely potent inhibitor of human renin (Ki = 1.3 X lo-lo M). Kinetic analyses by several techniques show reversible interaction of pepstatin with renin and classical noncofipetitive inhibition. The high affinity of pepstatin for renin allows kinetic determination of the molarity of the enzyme in partially purified preparations. This method has been validated by parallel studies of pepstatin inhibition of pure porcine pepsin. A widely used preparation of human renin has been shown to contain about 0.1% of the pure enzyme. The maximum theoretical specific activity of human renin has been calculated from this value at 118 Goldblatt units per mg of enzyme protein.