Mouse submaxillary renin: a useful model for the study of renal renin

The submaxillary gland of mouse contains a renin-like enzyme which represents as much as 5% of the total protein content. Its physico-chemical and enzymatic characteristics are similar to those of renal renin. Recently, the amino-acid sequence of the submaxillary pre-prorenin molecule has been deduced from the nucleotide sequence of the renin structural gene. A model for pre-prorenin processing into active renin has been proposed. Comparison of the structures of mouse submaxillary renin and of aspartyl proteases shows that renin belongs to this class of proteins and shares a similar catalytic site. Although the structure of renal renin is not yet known, preliminary studies suggest that the renal pro-enzyme is processed as the submaxillary enzyme. However, glycosylation would occur in the case of renal renin, whereas submaxillary renin is not glycosylated. Genetic studies and DNA hybridization experiments in mouse with high or low renin content in the submaxillary gland show that submaxillary renin in high renin producing strains results from a gene duplication. Submaxillary renin is therefore an isoenzyme and a useful model for the study of renal renin.