In molecular biology, the Signal Peptide Peptidase (SPP) is a type of protein that specifically cleaves parts of other proteins. It is an intramembraneaspartyl protease with the conserved active site motifs 'YD' and 'GxGD' in adjacent transmembrane domains (TMDs). Its sequences is highly conserved in different vertebrate species. SPP cleaves remnant signal peptides left behind in membrane by the action of signal peptidase[1] and also plays key roles in immune surveillance and the maturation of certain viral proteins.[2]