[Change of the thermostability of renin by glycosylation]

Inbred strains of mice, which produce high levels of submaxillary gland (SMG) renin have two renin genes, Ren 1 and Ren 2, per haploid genome, while strains with low levels of SMG renin have only the Ren 1 gene. Ren 1 codes for a glycosylated protein and Ren 2 codes for a highly homologous but unglycosylated and less thermostable protein. In order to determine if this difference in thermostability is related to the absence of glycosylation of renin-2 and/or to some amino acid difference between both renins we have compared the thermostability of renin-2 and a renin-2 mutant containing two potential N-glycosylation sites added by in vitro mutagenesis. Both mutant and wild type renins were expressed in AtT20 cells. Wild type renin was significantly less stable than the glycosylated mutant form upon heating. Moreover, the kinetics of heat inactivation of the mutant, in vitro deglycosylated form was similar to that of the wild type renin. This result indicates that glycosylation affects the thermostability of renin.