E. Devito et al., ACTIVATION OF RENAL RENIN BY A PROTEIN PLASMA FRACTION - A NOVEL ENZYMATIC MECHANISM, Comparative biochemistry and physiology. B. Comparative biochemistry, 113(2), 1996, pp. 433-438
A 3-fold increase in active renin was found after a kidney cortex extr
act was incubated with plasma from either normal or nephrectomized rat
s (0.34 +/- 0.04 to 1.34 +/- 0.08 and 1.60 +/- 0.06 mu g Angiotenson I
/mg tissue/hr, respectively). A plasma protein that activates renal re
nin was purified 900-fold. Purification of the protein was achieved by
a combination of ammonium sulfate fractionation, molecular filtration
on Sephacryl S-200 HR and ion-exchange chromatography on Mono Q HR 5/
5 associated to an fast performance liquid chromatography (FPLC) syste
m. The protein shows a molecular weight of similar to 54,000 Da. Renin
activation was not inhibited by serine protease inhibitors, such as p
henylmethyl sulfonylfluoride, aprotinin, soybean trypsin inhibitor and
N-tosyl-L-phenylalanine chloromethyl ketone or by the cystein proteas
e inhibitors N-ethylmaleimide and leupeptin. By using enzyme inhibitor
s, it was found that the activation process is not mediated by kallikr
ein, plasmin, tonin, cathepsin B or trypsin-like enzymes. From these r
esults, we conclude that there is in circulating plasma a previously u
nidentified enzyme capable of activating inactive kidney renin. Howeve
r, the possibility that this protein acts by activating the renin-subs
trate reaction cannot be dismissed.