Involved in the processing of hormone and other protein precursors at sites comprised of pairs of basic amino acid residues. Substrates include POMC, renin, enkephalin, dynorphin, somatostatin, insulin and AGRP. Release of protein hormones, neuropeptides and renin from their precursors, generally by hydrolysis of -Lys-Arg-|- bonds. Localized in the secretion granules. O-glycosylated. Genetic variations in PCSK1 define the body mass index quantitative trait locus 12 (BMIQ12) [MIM:612362]. Variance in body mass index is a susceptibility factor for obesity. The disease is caused by variants affecting the gene represented in this entry. Belongs to the peptidase S8 family. Furin subfamily.