Substrate Specificity of Human Renin: The Effect of Substitutions at the Amino Terminus and P3 Position of the Substrate
Renin (E.C. 220.127.116.11) regulates the initial step in the generation of the potent pressor octapeptide angiotensin II by cleaving the decapeptide angiotensin I from the amino terminus of angiotensinogen (Ondetti & Cushman, 1982). In contrast to structurally homologous cellular aspartic proteases, renin specificity is restricted to angiotensinogen and little variation from the substrate sequence is tolerated. Inspection of the crystal structure (Sielecki et al., 1989) indicates substrate residues P4 to P3′ (nomenclature of Schechter & Berger, 1967, where P1−P1′ is the scissile peptide bond) interact directly with renin. We have determined the steady-state kinetic parameters of human renin with substrates (Table 1) that differ in the amino terminal P7 to P10 residues (PTDP and KIHPFHLLVYS) and P3 residue (KIHPXHLLVYS). Our results are consistent with the structural predictions; that is, substitutions outside of the P4 to P3′ sequence have no significant effect on renin activity but substituting p-nitro-phenylalanine (pNF, X) for phenylalanine at the P3 position decreases the reactivity of renin.
KeywordsHuman Renin Scissile Bond Substrate Residue 1040A Diode Array Scissile Peptide Bond
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