Lysyl oxidase is a secreted copper containing enzyme that initiates the crosslinking of collagen and elastin by catalyzing oxidative deamination of lysine and hydroxylysine residues. Coded by the LOX gene at 5q23.3-q31.2 whose expression level seems to be very important in the metastatic process with cancer. It is expressed the most in heart, placenta, skeletal muscle, kidney, lung and pancreas. Mutations can cause autosomal recessive cutis laxa type I. There are a number of very similar genes which also may contribute to developmental and cell regulation or senescence and chemotaxis:
- LOXL1 - Widely expressed apart from CNS and which may code by analogy to a specific enzyme with elastin specificity
- Defects produce exfoliation glaucoma which is very common in the elderly.
- LOXL2 - Overexpressed in Werner syndrome. Highest expression in reproductive tissues, placenta, uterus and prostate.
- LOXL3 - Only member of the family to be expressed in the central nervous system. High levels expressed in placenta, heart, ovary, testis, small intestine and spleen.
- LOXL4 - Not expressed in leukocytes or many cancers but widely expressed at variable levels in other tissues. Highest levels in skeletal muscle, testis and pancreas with moderate expression in cartilage.