Magni et al. 2012 describe a novel serine-endopeptidase activity with cleavage specificity to twin-arginine pairs (-R-R-) in mature dry Lupinus albus seeds. The authors suggest that the activity of the novel endopeptidase is essential for degradation at germination and generates polypeptide fragments with specific biological activity. 
 Magni C, Sessa F, Tedeschi G, Negri A, Scarafoni A, Consonni A, Duranti M: Identification in Lupin Seed of a Serine-Endopeptidase Activity Cleaving between Twin Arginine Pairs and Causing Limited Proteolysis of Seed Storage Proteins. Mol Plant. 2012 Jan 4.