Oxytocin is produced by cleavage of the protein of the oxytocin/neurophysin I prepropeptide gene. The precursor peptide is cleaved by Proprotein-Convertase 1 . Mice lacking the gene which encodes for this enzyme have reduced levels of oxytocin. The final step in the biosynthesis of oxytocin is carried out by Peptidyl glycine alpha-amidating mono-oxygenase.