Skin Aspartic Protease (SASP)

SASP has a calculated molecular mass of 37 kD, and an alternate isoform of 259 amino acids has a molecular mass of 28.5 kD. SASP shares similarity with aspartyl proteases with a retroviral-type signature, such as the equine anemia virus (EIAV) protease. SASP contains a predicted N-myristoylation domain, a dileucine site, N-glycosylation, sulfation, phosphorylation, myristoylation, and amidation sites, and a putative transmembrane domain. SASP shares 87% amino acid homology with its mouse ortholog. Northern blot analysis of human tissues detected SASP expression primarily in skin with lower expression in brain. Western blot analysis of human epidermis detected 14-kD and 28-kD isoforms, and the authors suggested that the 14-kD form represents the activated protease while the 28-kD form is an epidermal proform SASP.