Furin is also known as paired basic Amino acid Cleaving Enzyme (PACE), is an enzyme which belongs to the subtilisin-like proprotein convertase family. The members of this family are proprotein convertases that process latent precursor proteins into their biologically active products. Furin is enriched in the Golgi apparatus, where it functions to cleave other proteins into their mature/active forms. The expression of furin in T-cells is required for maintenance of peripheral immune tolerance. Furin cleaves proteins just downstream of a basic amino acid target sequence (canonically, Arg-X-(Arg/Lys) -Arg'). PACE is a calcium-dependent serine endoprotease that can efficiently cleave precursor proteins at their paired basic amino acid processing sites. In addition to processing cellular precursor proteins, furin is also utilized by a number of pathogens. For example, the envelope proteins of viruses such as HIV, influenza and dengue fever viruses must be cleaved by furin or furin-like proteases to become fully functional. PACE also play a role in tumor progression.