10 - Renin

Abstract

This chapter describes the structural chemistry and the biological aspects of renin. Renin has no known physiological effect other than the proteolysis of renin substrate, angiotensinogen. It belongs to the class of enzyme called aspartyl proteinases. Renin differs from the other members of this class by having a pH optimum of 5.5–7.5 instead of 2.0–3.4. The pH dependence of renin activity using native substrates, and synthetic substrates has an optimum range from 5.5 to 7.0 depending on renin species and the substrate used. The affinity constant of renin for its native substrate is approximately the same as the synthetic substrates. Native renin is a two-chain protein of about 36–42 kDa, pI 5.0–5.2, which contains two disulfide bonds. Two N-glycosylation sites can be indicated by amino acid sequence deduced from renin cDNAs of human and rat. The recombinant enzyme is a single-chain protein of about 42 kDa. The reaction mechanism of renin has been investigated with respect to both substrate and enzyme. The His residues at the P2 site in angiotensinogen has been proposed to participate in the catalytic step.