In vitro metabolism of LVV-Hemorphin-7 by renal cytosol and purified prolyl endopeptidase

The metabolism of LVVH7, an endogenous peptide obtained by cathepsin D hydrolysis of the beta chain of hemoglobin, was studied, in vitro, in the presence of cytosol of rat kidney and compared with angiotensin IV. High metabolic activity was found against these two peptides (half life time < 2 min) in this subcellular fraction. The main products of LVVH7 metabolism by renal cytosol are VVH7, H7 and LVVH6 suggesting both aminopeptidase and carboxypeptidase activities. The use of PEP inhibitor in kidney cytosol permitted to demonstrate the major role of prolyl endopeptidase (PEP) in LVVH7 degradation. This fact was reinforced by a kinetic study investigated with purified enzyme (Km/Vmax about 238 mM-1 s-1 and close to that observed for angiotensin related peptides).