PCSK4 is involved in the processing of hormone and other protein precursors at sites comprised of pairs of basic amino acid residues. PCSK4 plays a role in transcriptional coactivation. PCSK4 may be involved in stabilizing the multiprotein transcription complex.Proprotein convertases, including PCSK4, are calcium-dependent serine proteases related to bacterial subtilisins and to yeast kexin. These enzymes process precursor proteins to their active forms by selective cleavage of the polypeptide at sites following paired basic amino acids. In mammals, this family comprises PC1 (MIM 162150), PC2 (MIM 162151), PC4, PC5 (MIM 600488), furin (FUR, MIM 136950), and PACE4 (MIM 167405). Substrates for these enzymes range from prohormones to precursors for growth factors to cell surface receptors and viral surface glycoproteins (Cao et al., 2001 [PubMed 11776387]).