Lysyl oxidase

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Lysyl oxidase
Lysyl oxidase.png
Symbols LOX ; MGC105112
External IDs OMIM153455 MGI96817 HomoloGene1741 ChEMBL: 2249 GeneCards: LOX Gene
EC number
RNA expression pattern
PBB GE LOX 215446 s at tn.png
PBB GE LOX 204298 s at tn.png
PBB GE LOX 213640 s at tn.png
More reference expression data
Species Human Mouse
Entrez 4015 16948
Ensembl ENSG00000113083 ENSMUSG00000024529
UniProt P28300 P28301
RefSeq (mRNA) NM_001178102 NM_010728
RefSeq (protein) NP_001171573 NP_034858
Location (UCSC) Chr 5:
121.4 – 121.41 Mb
Chr 18:
52.52 – 52.53 Mb
PubMed search [1] [2]

Lysyl oxidase (LOX), also known as protein-lysine 6-oxidase, is a protein that, in humans, is encoded by the LOX gene.[1][2] Its inhibition can cause lathyrism, but, at the same time, its upregulation by tumor cells may promote metastasis of the existing tumor, causing it to become malignant and cancerous.


In the yeast strain Pichia pastoris, lysyl oxidase constitutes a homodimeric structure. Each monomer consists of an active site that includes a Cu(II) atom coordinated with three histidine residues as well as 2,4,5-trihydroxyphenalanine quinone (TPQ), a crucial cofactor.[3]

In humans, the LOX gene is located on chromosome 5q23.3-31.2. The DNA sequence encodes a polypeptide of 417 amino acids, the first 21 residues of which constitute a signal peptide,[2] with a weight of approximately 32 kDa.[4] The carboxyterminus contains the active copper (II) ion, lysine, tyrosine, and cysteine residues that comprise the catalytically active site.[5] The three-dimensional structure of human lysyl oxidase has not yet been resolved.[6]


Lox mechanism

The mechanism of lysyl oxidase occurs via modification of the ε-amino group of a lysine side chain.[4] The enzyme falls into the category of quinone-containing copper amine oxidases, and the reaction is highly dependent on the cofactor lysyl tyrosylquinone (LTQ). The LTQ cofactor is unique among quinones due to its ortho/benzoquinone structure and neutral charge under physiological pH. This can be contrasted with the similar ubiquitous quinocofactor TPQ, which exists as a negatively charged structure under physiological conditions and includes ortho/para-carbonyl resonance functionality.[7]

LTQ is crucial in LOX-catalyzed conversion of lysine residues to α-aminoadipidic-δ-semialdehydes, generally referred to as allysines.[8] In the oxidation of lysine, the ε-amine is first converted to a Schiff base via reaction with LTQ. While LTQ is still bound to the substrate, rate-limiting removal of the ε-proton yields an imine intermediate. Subsequent hydrolysis of the imine leads to release of the aldehyde product, allysine. Molecular oxygen and the copper ion are utilized to reoxidize the cofactor and yield another imine, producing hydrogen peroxide as a side product. Additional hydrolysis releases ammonia and the original cofactor, completing the catalytic cycle.[9]

Biological function[edit]

Lysyl oxidase is an extracellular copper enzyme that catalyzes formation of aldehydes from lysine residues in collagen and elastin precursors.[10][11] These aldehydes are highly reactive, and undergo spontaneous chemical reactions with other lysyl oxidase-derived aldehyde residues, or with unmodified lysine residues. This results in cross-linking collagen and elastin, which is essential for stabilization of collagen fibrils and for the integrity and elasticity of mature elastin.[1]

Complex cross-links are formed in collagen (pyridinolines derived from three lysine residues) and in elastin (desmosines derived from four lysine residues) that differ in structure.[12]

The importance of lysyl oxidase-derived cross-linking was established from animal studies in which lysyl oxidase was inhibited either by nutritional copper-deficiency or by supplementation of diets with β-aminopropionitrile (BAPN), an inhibitor of lysyl oxidase.[13] This resulted in lathyrism, characterized by poor bone formation and strength, hyperextensible skin, weak ligaments, and increased occurrence of aortic aneurysms. These abnormalities correlated well with decreased cross-linking of collagen and elastin.[14]

Developmentally, reduced lysyl oxidase levels have been implicated in Menkes disease and Occipital horn syndrome, two X-linked recessive disorders characterized by a mutation in a gene for copper transportation. Thus, not only is LOX crucial to cardiovascular development, it is thought to play a major role in connective tissue development and may also be important in neurological function.[15]

Lysyl oxidase has also proven crucial to the development of the respiratory system and the skin, as collagen and elastin represent 50-60% of the composition of the lung, and 75% of the skin. In LOX double knockout models (Lox -/-), function of LOX was reduced by up to 80%, and the phenotype of the lungs resembles those of human patients with emphysema and dilated distal airways.[15]

Finally, lysyl oxidase plays a crucial role in the commitment step of adipocyte, or fat cell, formation from pluripotent stem cells during development. Its absence may lead to defects in the transforming growth factor beta superfamily of proteins, which control cell growth and differentiation.[16]

Clinical significance[edit]

LOX expression is regulated by hypoxia-inducible factors (HIFs), and, hence, LOX expression is often upregulated in hypoxic breast and head and neck tumors. Patients with high LOX-expressing tumors have poor overall survival. Furthermore, inhibition of LOX has been demonstrated to eliminate metastases in mice. Secreted LOX is responsible for the invasive properties of hypoxic cancer cells through focal adhesion kinase activity and cell-to-matrix adhesion. LOX may be required to create a niche permissive for metastatic growth and, thus, may be required for hypoxia-induced metastasis.[17] In fact, recent research has shown overexpression of LOX as crucial to promoting tumor growth and metastasis in several cancers, including breast cancer,[18] melanoma,[19] non-small cell lung cancer,[20] and colorectal cancer.[21]

LOX expression was also detected in megakaryocytes, or bone marrow cells responsible for the production of platelets. Data derived from a mouse model of myelofibrosis implicated LOX in bone marrow fibrosis.

In a rodent model of breast cancer, a small-molecule or antibody inhibitors of LOX abolished metastasis.[22] LOX secreted by hypoxic breast tumor cells crosslinks collagen in the basement membrane and is essential for CD11b+ myeloid cell recruitment. CD11b+ cells in turn adhere to crosslinked collagen and produce matrix metalloproteinase-2, which cleaves collagen, enhancing the invasion of metastasizing tumor cells. In contrast, LOX inhibition prevents CD11b+ cell recruitment and metastatic growth.[23]

In cells lacking TGF-β receptors, a deficiency that is characteristic of lung cancer, lysyl oxidase is found in high concentrations. LOX immunostaining has revealed that high LOX expression is associated with high extent of carcinoma invasion in samples obtained from surgically removed lung adenocarcinomas. Additionally, LOX expression is an indicator of 5-year survival in patients, with a 71% chance of survival for patients with low LOX levels, compared to 43% for patients with high LOX levels. Thus, upregulation of lysyl oxidase is a predictor of poor prognosis in early-stage adenocarcinoma patients.[24]

Lysyl oxidase has been newly implicated in tumor angiogenesis, or blood vessel formation, both in vivo and in vitro. Subcutaneous tumor-derived LOX was shown to increase vascular endothelial growth factor (VEGF) expression and secretion, which then promotes angiogenesis by phosphorylation of protein kinase B, or Akt, through platelet-derived growth factor receptor β (PDGFRB). High levels of LOX were associated with high blood vessel density in patient samples. Clinically relevant LOX inhibitors may help slow cancer progression by downregulating crucial growth factors that promote solid tumor progression.[25]

Hence, inhibitors of the LOX enzyme may be useful in preventing angiogenesis, tumor progression, and metastasis as well as treating other fibrotic disease involving remodeling of the extracellular matrix, including neurodegenerative and cardiovascular diseases.[26]

See also[edit]


  1. ^ a b "Entrez Gene: LOX lysyl oxidase". 
  2. ^ a b Hämäläinen ER, Jones TA, Sheer D, Taskinen K, Pihlajaniemi T, Kivirikko KI (November 1991). "Molecular cloning of human lysyl oxidase and assignment of the gene to chromosome 5q23.3-31.2". Genomics 11 (3): 508–16. doi:10.1016/0888-7543(91)90057-L. PMID 1685472. 
  3. ^ Duff AP, Cohen AE, Ellis PJ, Kuchar JA, Langley DB, Shepard EM, Dooley DM, Freeman HC, Guss JM (December 2003). "The crystal structure of Pichia pastoris lysyl oxidase". Biochemistry 42 (51): 15148–57. doi:10.1021/bi035338v. PMID 14690425. 
  4. ^ a b Gacheru SN, Trackman PC, Shah MA, O'Gara CY, Spacciapoli P, Greenaway FT, Kagan HM (November 1990). "Structural and catalytic properties of copper in lysyl oxidase". J. Biol. Chem. 265 (31): 19022–7. doi:10.1016/0162-0134(89)84532-5. PMID 1977746. 
  5. ^ Thomassin L, Werneck CC, Broekelmann TJ, Gleyzal C, Hornstra IK, Mecham RP, Sommer P (December 2005). "The Pro-regions of lysyl oxidase and lysyl oxidase-like 1 are required for deposition onto elastic fibers". J. Biol. Chem. 280 (52): 42848–55. doi:10.1074/jbc.M506832200. PMID 16251195. 
  6. ^ Kagan HM, Li W (March 2003). "Lysyl oxidase: properties, specificity, and biological roles inside and outside of the cell". J. Cell. Biochem. 88 (4): 660–72. doi:10.1002/jcb.10413. PMID 12577300. 
  7. ^ Wang SX, Nakamura N, Mure M, Klinman JP, Sanders-Loehr J (November 1997). "Characterization of the native lysine tyrosylquinone cofactor in lysyl oxidase by Raman spectroscopy". J. Biol. Chem. 272 (46): 28841–4. doi:10.1074/jbc.272.46.28841. PMID 9360949. 
  8. ^ Bedell-Hogan D, Trackman P, Abrams W, Rosenbloom J, Kagan H (May 1993). "Oxidation, cross-linking, and insolubilization of recombinant tropoelastin by purified lysyl oxidase". J. Biol. Chem. 268 (14): 10345–50. PMID 8098038. 
  9. ^ Akagawa M, Suyama K (February 2001). "Characterization of a model compound for the lysine tyrosylquinone cofactor of lysyl oxidase". Biochem. Biophys. Res. Commun. 281 (1): 193–9. doi:10.1006/bbrc.2001.4315. PMID 11178979. 
  10. ^ Alberts, Bruce (2002). Molecular biology of the cell. New York: Garland Science. p. 1099. ISBN 0-8153-3218-1. 
  11. ^ Csiszar K (2001). "Lysyl oxidases: a novel multifunctional amine oxidase family". Prog. Nucleic Acid Res. Mol. Biol. Progress in Nucleic Acid Research and Molecular Biology 70: 1–32. doi:10.1016/S0079-6603(01)70012-8. ISBN 9780125400701. PMID 11642359. 
  12. ^ Siegel RC, Fu JC, Uto N, Horiuchi K, Fujimoto D (October 1982). "Collagen cross-linking: lysyl oxidase dependent synthesis of pyridinoline in vitro: confirmation that pyridinoline is derived from collagen". Biochem. Biophys. Res. Commun. 108 (4): 1546–50. doi:10.1016/S0006-291X(82)80083-1. PMID 6129847. 
  13. ^ Dawson DA, Rinaldi AC, Pöch G (August 2002). "Biochemical and toxicological evaluation of agent-cofactor reactivity as a mechanism of action for osteolathyrism". Toxicology 177 (2–3): 267–84. doi:10.1016/S0300-483X(02)00233-0. PMID 12135629. 
  14. ^ Wilmarth KR, Froines JR (November 1992). "In vitro and in vivo inhibition of lysyl oxidase by aminopropionitriles". J Toxicol Environ Health 37 (3): 411–23. doi:10.1080/15287399209531680. PMID 1359158. 
  15. ^ a b Mäki JM, Sormunen R, Lippo S, Kaarteenaho-Wiik R, Soininen R, Myllyharju J (October 2005). "Lysyl oxidase is essential for normal development and function of the respiratory system and for the integrity of elastic and collagen fibers in various tissues". Am. J. Pathol. 167 (4): 927–36. doi:10.1016/S0002-9440(10)61183-2. PMC 1603668. PMID 16192629. 
  16. ^ Huang HY, Chen SZ, Zhang WT, Wang SS, Liu Y, Li X, Sun X, Li YM, Wen B, Lei QY, Tang QQ (January 2013). "Induction of EMT-like response by BMP4 via up-regulation of lysyl oxidase is required for adipocyte lineage commitment". Stem Cell Res 10 (3): 278–287. doi:10.1016/j.scr.2012.12.005. PMID 23395997. 
  17. ^ Erler JT, Bennewith KL, Nicolau M, Dornhöfer N, Kong C, Le QT, Chi JT, Jeffrey SS, Giaccia AJ (April 2006). "Lysyl oxidase is essential for hypoxia-induced metastasis". Nature 440 (7088): 1222–6. doi:10.1038/nature04695. PMID 16642001. 
  18. ^ El-Haibi CP, Bell GW, Zhang J, Collmann AY, Wood D, Scherber CM, Csizmadia E, Mariani O, Zhu C, Campagne A, Toner M, Bhatia SN, Irimia D, Vincent-Salomon A, Karnoub AE (October 2012). "Critical role for lysyl oxidase in mesenchymal stem cell-driven breast cancer malignancy". Proc. Natl. Acad. Sci. U.S.A. 109 (43): 17460–5. doi:10.1073/pnas.1206653109. PMID 23033492. 
  19. ^ Kirschmann DA, Seftor EA, Fong SF, Nieva DR, Sullivan CM, Edwards EM, Sommer P, Csiszar K, Hendrix MJ (August 2002). "A molecular role for lysyl oxidase in breast cancer invasion". Cancer Res. 62 (15): 4478–83. PMID 12154058. 
  20. ^ Shi W, Yang B, Li X, Sun S, Wang L, Jiao S (December 2012). "The effect of lysyl oxidase polymorphism on susceptibility and prognosis of nonsmall cell lung cancer". Tumour Biol. 33 (6): 2379–83. doi:10.1007/s13277-012-0501-5. PMID 22948781. 
  21. ^ Baker AM, Cox TR, Bird D, Lang G, Murray GI, Sun XF, Southall SM, Wilson JR, Erler JT (March 2011). "The role of lysyl oxidase in SRC-dependent proliferation and metastasis of colorectal cancer". J. Natl. Cancer Inst. 103 (5): 407–24. doi:10.1093/jnci/djq569. PMID 21282564. 
  22. ^ Erler JT, Giaccia AJ (November 2006). "Lysyl oxidase mediates hypoxic control of metastasis". Cancer Res. 66 (21): 10238–41. doi:10.1158/0008-5472.CAN-06-3197. PMID 17079439. 
  23. ^ Erler JT, Bennewith KL, Cox TR, Lang G, Bird D, Koong A, Le QT, Giaccia AJ (January 2009). "Hypoxia-induced lysyl oxidase is a critical mediator of bone marrow cell recruitment to form the premetastatic niche". Cancer Cell 15 (1): 35–44. doi:10.1016/j.ccr.2008.11.012. PMC 3050620. PMID 19111879. 
  24. ^ Wilgus ML, Borczuk AC, Stoopler M, Ginsburg M, Gorenstein L, Sonett JR, Powell CA (May 2011). "Lysyl oxidase: a lung adenocarcinoma biomarker of invasion and survival". Cancer 117 (10): 2186–91. doi:10.1002/cncr.25768. PMID 21523732. 
  25. ^ Baker AM, Bird D, Welti JC, Gourlaouen M, Lang G, Murray GI, Reynolds AR, Cox TR, Erler JT (January 2013). "Lysyl oxidase plays a critical role in endothelial cell stimulation to drive tumor angiogenesis". Cancer Res. 73 (2): 583–94. doi:10.1158/0008-5472.CAN-12-2447. PMID 23188504. 
  26. ^ Rodríguez C, Rodríguez-Sinovas A, Martínez-González J (May 2008). "Lysyl oxidase as a potential therapeutic target". Drug News Perspect. 21 (4): 218–24. doi:10.1358/dnp.2008.21.4.1213351. PMID 18560621. 

Further reading[edit]

  • Csiszar K (2001). "Lysyl oxidases: a novel multifunctional amine oxidase family". Prog. Nucleic Acid Res. Mol. Biol. Progress in Nucleic Acid Research and Molecular Biology 70: 1–32. doi:10.1016/S0079-6603(01)70012-8. ISBN 9780125400701. PMID 11642359. 
  • Kagan HM, Li W (2003). "Lysyl oxidase: properties, specificity, and biological roles inside and outside of the cell". J. Cell. Biochem. 88 (4): 660–72. doi:10.1002/jcb.10413. PMID 12577300. 
  • Svinarich DM, Twomey TA, Macauley SP, Krebs CJ, Yang TP, Krawetz SA (1992). "Characterization of the human lysyl oxidase gene locus". J. Biol. Chem. 267 (20): 14382–7. PMID 1352776. 
  • Mariani TJ, Trackman PC, Kagan HM, Eddy RL, Shows TB, Boyd CD, Deak SB (1992). "The complete derived amino acid sequence of human lysyl oxidase and assignment of the gene to chromosome 5 (extensive sequence homology with the murine ras recision gene)". Matrix 12 (3): 242–8. doi:10.1016/S0934-8832(11)80067-3. PMID 1357535. 
  • Murawaki Y, Kusakabe Y, Hirayama C (1992). "Serum lysyl oxidase activity in chronic liver disease in comparison with serum levels of prolyl hydroxylase and laminin". Hepatology 14 (6): 1167–73. doi:10.1002/hep.1840140635. PMID 1683640. 
  • Hämäläinen ER, Jones TA, Sheer D, Taskinen K, Pihlajaniemi T, Kivirikko KI (1992). "Molecular cloning of human lysyl oxidase and assignment of the gene to chromosome 5q23.3-31.2". Genomics 11 (3): 508–16. doi:10.1016/0888-7543(91)90057-L. PMID 1685472. 
  • Konishi A, Iguchi H, Ochi J, Kinoshita R, Miura K, Uchino H (1985). "Increased lysyl oxidase activity in culture medium of nonparenchymal cells from fibrotic livers". Gastroenterology 89 (4): 709–15. PMID 2863189. 
  • Kuivaniemi H, Ala-Kokko L, Kivirikko KI (1986). "Secretion of lysyl oxidase by cultured human skin fibroblasts and effects of monensin, nigericin, tunicamycin and colchicine". Biochim. Biophys. Acta 883 (2): 326–34. doi:10.1016/0304-4165(86)90325-9. PMID 2874833. 
  • Reiser KM, Hennessy SM, Last JA (1988). "Analysis of age-associated changes in collagen crosslinking in the skin and lung in monkeys and rats". Biochim. Biophys. Acta 926 (3): 339–48. doi:10.1016/0304-4165(87)90220-0. PMID 3120785. 
  • Järveläinen H, Halme T, Rönnemaa T (1982). "Effect of cortisol on the proliferation and protein synthesis of human aortic smooth muscle cells in culture". Acta Med. Scand. Suppl. 660: 114–22. PMID 6127904. 
  • Kuivaniemi H, Savolainen ER, Kivirikko KI (1984). "Human placental lysyl oxidase. Purification, partial characterization, and preparation of two specific antisera to the enzyme". J. Biol. Chem. 259 (11): 6996–7002. PMID 6144680. 
  • Lien YH, Stern R, Fu JC, Siegel RC (1984). "Inhibition of collagen fibril formation in vitro and subsequent cross-linking by glucose". Science 225 (4669): 1489–91. doi:10.1126/science.6147899. PMID 6147899. 
  • Yasutake A, Powers JC (1981). "Reactivity of human leukocyte elastase and porcine pancreatic elastase toward peptide 4-nitroanilides containing model desmosine residues. Evidence that human leukocyte elastase is selective for cross-linked regions of elastin". Biochemistry 20 (13): 3675–9. doi:10.1021/bi00516a002. PMID 6912069. 
  • Kim Y, Boyd CD, Csiszar K (1995). "A new gene with sequence and structural similarity to the gene encoding human lysyl oxidase". J. Biol. Chem. 270 (13): 7176–82. doi:10.1074/jbc.270.13.7176. PMID 7706256. 
  • Hämäläinen ER, Kemppainen R, Pihlajaniemi T, Kivirikko KI (1993). "Structure of the human lysyl oxidase gene". Genomics 17 (3): 544–8. doi:10.1006/geno.1993.1369. PMID 7902322. 
  • Forbes EG, Cronshaw AD, MacBeath JR, Hulmes DJ (1994). "Tyrosine-rich acidic matrix protein (TRAMP) is a tyrosine-sulphated and widely distributed protein of the extracellular matrix". FEBS Lett. 351 (3): 433–6. doi:10.1016/0014-5793(94)00907-4. PMID 8082810. 
  • Csiszar K, Mariani TJ, Gosin JS, Deak SB, Boyd CD (1993). "A restriction fragment length polymorphism results in a nonconservative amino acid substitution encoded within the first exon of the human lysyl oxidase gene". Genomics 16 (2): 401–6. doi:10.1006/geno.1993.1203. PMID 8100215. 
  • Vetter U, Weis MA, Mörike M, Eanes ED, Eyre DR (1993). "Collagen crosslinks and mineral crystallinity in bone of patients with osteogenesis imperfecta". J. Bone Miner. Res. 8 (2): 133–7. doi:10.1002/jbmr.5650080203. PMID 8442432. 
  • Panchenko MV, Stetler-Stevenson WG, Trubetskoy OV, Gacheru SN, Kagan HM (1996). "Metalloproteinase activity secreted by fibrogenic cells in the processing of prolysyl oxidase. Potential role of procollagen C-proteinase". J. Biol. Chem. 271 (12): 7113–9. doi:10.1074/jbc.271.12.7113. PMID 8636146. 
  • Khakoo A, Thomas R, Trompeter R, Duffy P, Price R, Pope FM (1997). "Congenital cutis laxa and lysyl oxidase deficiency". Clin. Genet. 51 (2): 109–14. doi:10.1111/j.1399-0004.1997.tb02430.x. PMID 9111998. 

External links[edit]