PCSK4(Proprotein Convertase, Subtilisin/Kexin-Type, 4), is an enzyme that in humans is encoded by the PCSK4 gene. The gene for PC4(Pcsk4 locus) was mapped to mouse chromosome 10, close to the adipsin locus and near the gene encoding anti-mullerian hormone. Qiu et al.(2005) found that aberrant processing of pro-IGF2 by PC4 may be a cause of IUGR. PC4 cleaved pro-IGF2 to generate the intermediate processed form, IGF2(1-102). Mature IGF2(1-67), likely resulting from further processing by carboxypeptidases, is capable of activating invasive trophoblast cells through AKT phosphorylation. Inhibition of PC4 by a PC4-specific inhibitor blocked pro-IGF2 processing and reduced trophoblast cell migration.