title: The reversible activation of inactive renin in human plasma: role of acid and of plasma kallikrein and plasmin.
abstract: Inactive renin in normal plasma, Factor XII-deficient plasma and prekallikrein-deficient plasma was fully activated by dialysis to pH 3.0 for 24 hours at 4 degrees C. This activation was reversed after neutralization and incubation of the plasma at 37 degrees C. The reversible activation-inactivation was not affected by the presence of soya bean trypsin inhibitor. If acidified normal plasma was neutralized and stood at 4 degrees C, plasma kallikrein, but not plasmin, was generated. This rendered the initial acid-activation irreversible. Since no kallikrein was generated in the deficient plasmas, the acid-activation was reversible in these plasmas even after neutralization and standing at 4 degrees C. Thus the apparent activation of inactive renin by kallikrein in acidified, neutralized plasma is not a direct action by the serine protease on inactive renin but a two-stage process in which the inactive renin is first fully activated by acid treatment and the reverse reaction is prevented by plasma kallikrein.
mesh_terms: D003080:Cold Temperature; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000097:blood*; D005175:Factor XII Deficiency / Q000201:enzymology; D005341:Fibrinolysin / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007610:Kallikreins / Q000097:blood*; D007700:Kinetics; D008297:Male; D012083:Renin / Q000097:blood*
chemical_list: D004792:Enzyme Precursors; D007610:Kallikreins; D005341:Fibrinolysin; D012083:Renin