LOXL3-sv2, a novel variant of human lysyl oxidase-like 3 (LOXL3), functions as an amine oxidase.

Abstract

Human lysyl oxidase-like 3(LOXL3) functions as a copper-dependent amine oxidase toward collagen and elastin. The LOXL3protein contains four scavenger receptor cysteine-rich(SRCR) domains in the N-terminus in addition to the C-terminal characteristic domains of the lysyl oxidase(LOX) family, such as a copper-binding domain, a cytokine receptor‑like domain and residues for the lysyl-tyrosyl quinone cofactor. Using BLASTNsearches, we identified a novel variant of LOXL3(termed LOXL3-sv2), which lacked the sequences corresponding to exons4 and5 of LOXL3. The LOXL3-sv2mRNA is at least 2,398bp in length, encoding a 608amino acid-long polypeptide with a calculated molecular mass of 67.4kDa. The deletion of exons4 and5 do not change the open-reading frame of LOXL3 but results in deletion of the SRCR domain2. The recombinant LOXL3-sv2protein showed a β-aminopropionitrile-inhibitable amine oxidase activity toward collagen typeI. In RT-PCR analysis, LOXL3-sv2 was detected in all human tissues tested, along with LOXL3 and LOXL3-sv1, a previously identified variant of LOXL3. These findings indicate that the human LOXL3gene encodes at least three variants, LOXL3, LOXL3-sv1 andLOXL3-sv2, all of which function as amine oxidases.