The Coexistence of Ser84 in Renin and His13 in Angiotensinogen Brings a pH Profile of Two Separate Peaks to the Reaction of Human Renin and Sheep Angiotensinogen

Abstract

The pH dependence and kinetics parameters of renin-angiotensinogen reactions were determined using wild-type and S84G mutant human renins and wild-type and H13Y mutant sheep angiotensinogens. It is explained in this report that (i) renin catalyzes acidic and basic reactions of which the optimum pHs are 5.5 and 7.5–8.2 respectively, both of which produce angiotensin I; (ii) Ser84 specific to human renin accelerates the acidic reaction by 75–110% through elevation of V_max, and shifts the optimum pH of the basic reaction from 7.5 to 8.0–8.2; and (iii) His13 specific to sheep angiotensinogen accelerates the acidic and basic reactions by 25–42% through reduction of K_m. It is concluded from these results that the coexistence of Ser84 in renin and His13 in angiotensinogen brings a pH profile of two separate peaks at pHs 5.5 and 8.2 to the reaction of human renin and sheep angiotensinogen.