The protein encoded by this gene is an extracellular copper enzyme that initiates the crosslinking of collagens and elastin. The enzyme catalyzes oxidative deamination of the epsilon-amino group in certain lysine and hydroxylysine residues of collagens and lysine residues of elastin. In addition to crosslinking extracellular matrix proteins, the encoded protein may have a role in tumor suppression. Defects in this gene are a cause of autosomal recessive cutis laxa type I (CL type I). Two transcript variants encoding different isoforms have been found for this gene.