Isolation and characterizaion of renin processing enzyme from renin granule

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Processing mechanism of prorenin to renin is still controversial. It is postulated that renin is synthesized and processed in the rough endoplasmic reticulum and the Golgi complex and stored in the renin granules and secreted by exocytosis. Recently several processing enzymes which process prohormones or protein precursors were found and identified as intrinsic processing enzymes.The purpose of this study was to clarify the nature of the intrinsic renin processing enzyme in the subcellular fraction of the kidney cortex. Generally prohormone convertases or protein precursor processing enzymes were reported to a common catalytic domain homologous to that of the subtilisin serine protease family.Hence in the first step of the present study, we investigated whether subtilisin per se can process prorenin to renin. When radiolabelled[^<35>S]-human recombinant prorenin was incubated with subtilisin BNP^-, human recombinant prorenin which showed a molecular weight of 43,000 dalton was cleaved … More to renin, a molecular weight of 38,000 dalton. In addition, when semipurified human amniotic prorenin(or inactive renin) was incubated with subtilisin, we confirmed the activation of prorenin by subtilisin by detection of active renin which was quantitated by a specific immunoradiometric assay system. These results indicate that subtilisin per se can process and activate prorenin to active form.In the next study, we investigated whether renin granule fraction of the kidney can process recombinant human prorenin to renin by cleaving prosegment of the prorenin. Human prorenin (molecular weight 43,000) was cleaved to renin (molecular weight 38,000) by renin granule fraction. This result suggests that renin granule fraction contained prorenin processing enzyme. In this study, we tried to isolate the prorenin processing enzyme from renin granule fraction, but we could noto isolate or identified prorenin processing enzyme in the renin granule because of loss of activity probably due to its lability during isolation. Less