Key Points
- To determine the molecular mechanism and reaction kinetics of acid-induced conversion of prorenin into active renin in human fluid samples and purified preparations.
- Evaluated acid activation kinetics of prorenin in human plasma, amniotic fluid, and purified prorenin preparations across acidic and neutral pH conditions.
- Separated the intermediate activated prorenin (pRa) from active renin (R) using Cibacron blue F3GA-agarose affinity chromatography and monoclonal antibody immunoassays.
- Measured second-order rate constants (kcat/Km) for the proteolytic cleavage of pRa to R by plasmin and plasma kallikrein at pH 7.4 and 37 °C.
- Prorenin conversion operates via a two-step mechanism: an acid-induced reversible conformational shift governed by polar group protonation (pK ≈ 3.4), followed by non-autocatalytic proteolytic cleavage.
- Proteolytic cleavage of pRa into active renin is mediated by an endogenous aspartic protease at low pH in amniotic fluid, and by plasma kallikrein at neutral pH in plasma.
- Catalytic efficiencies (kcat/Km) at pH 7.4 and 37 °C were 7.8 × 10^6 M^-1 min^-1 for plasmin and 5.2 × 10^6 M^-1 min^-1 for plasma kallikrein, representing a 50- to 70-fold increase compared with native prorenin.
Structured PICO
PPopulationHuman amniotic fluid and plasma, and preparations of purified prorenin isolated from amniotic fluid and plasma
IInterventionAcid activation (low pH) and proteolytic cleavage (plasmin, plasma kallikrein)
OOutcomeKinetics of acid activation of prorenin and conversion to active reninsurrogate
Prorenin activation is a two-step process involving an acid-induced reversible conformational change to an intermediary form, followed by proteolytic cleavage.