Activation of renal renin by a protein plasma fraction: a novel enzymatic mechanism.
A 3-fold increase in active renin was found after a kidney cortex extract was incubated with plasma from either normal or nephrectomized rats (0.34 +/- 0.04 to 1.34 +/- 0.08 and 1.60 +/- 0.06 micrograms Angiotensin I/mg tissue/hr, respectively). A plasma protein that activates renal renin 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) system. The protein shows a molecular weight of approximately 54,000 Da. Renin activation was not inhibited by serine protease inhibitors, such as phenylmethyl sulfonylfluoride, aprotinin, soybean trypsin inhibitor and N-tosyl-L-phenylalanine chloromethyl ketone or by the cystein protease inhibitors N-ethylmaleimide and leupeptin. By using enzyme inhibitors, it was found that the activation process is not mediated by kallikrein, plasmin, tonin, cathepsin B or trypsin-like enzymes. From these results, we conclude that there is in circulating plasma a previously unidentified enzyme capable of activating inactive kidney renin. However, the possibility that this protein acts by activating the renin-substrate reaction cannot be dismissed.
De Vito
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Instituto Superior de Investigaciones Biológicas (INSIBIO), Universidad Nacional de Tucumán, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.
Martinez de Melián
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Guardia
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D000818:Animals; D001798:Blood Proteins / Q000302:isolation & purification / Q000494:pharmacology* / Q000502:physiology; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004789:Enzyme Activation; D005260:Female; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000201:enzymology*; D007700:Kinetics; D009392:Nephrectomy; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012083:Renin / Q000378:metabolism*; D014462:Ultrafiltration
D001798:Blood Proteins; D011480:Protease Inhibitors; D012083:Renin