Lysyl oxidase explained

Lysyl oxidase should not be confused with Lipoxygenase.

Lysyl oxidase (LOX), also known as protein-lysine 6-oxidase, is an enzyme that, in humans, is encoded by the LOX gene.^{[1] [2]} It catalyzes the conversion of lysine residues into its aldehyde derivative allysine.^[3] Allysine form cross-links in extracellular matrix proteins. Inhibition of lysyl oxidase can cause osteolathyrism, but, at the same time, its upregulation by tumor cells may promote metastasis of the existing tumor, causing it to become malignant and cancerous.

Structure

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

In humans, the LOX gene is located on chromosome 5 q23.3-31.2. 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.^[5] The carboxyterminus contains the active copper (II) ion, lysine, tyrosine, and cysteine residues that comprise the catalytically active site.^[6] The three-dimensional structure of human lysyl oxidase has not yet been resolved.^[7]

Mechanism

Lysyl oxidase the terminal carbon of the side chain of lysyl residue side chain.^[5] The enzyme belongsthe category of quinone-containing copper amine oxidases. The reaction requires the cofactor lysyl tyrosylquinone (LTQ). The LTQ cofactor is unique among quinones because it contains an 1,2-benzoquinone substituent. Furthermore, it is neutral charge at physiological pH.^{[8] [9]} The ε-amine is condenses with LTQ to give the Schiff base via reaction with LTQ. The rate-limiting removal of a ε-proton yields an imine. Subsequent hydrolysis of the imine leads to release of the allysine residue. Molecular oxygen and the copper ion are utilized to reoxidize the cofactor, producing hydrogen peroxide as a side product.^[10]

Biological function

Lysyl oxidase is an extracellular copper-dependent enzyme that catalyzes formation of aldehydes from lysine residues in collagen and elastin precursors.^{[11] [12]} These aldehydes react with unmodified lysine residues, resulting 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.^[13]

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.^[14] 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.^[15]

Developmentally, reduced lysyl oxidase activity have been implicated in Menkes disease and occipital horn syndrome, two X-linked recessive disorders characterized by a mutation in a gene coding for a protein involved in copper transport. Thus, not only is LOX crucial to cardiovascular development, it plays a major role in connective tissue development and may also be important in neurological function.^[16]

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 homozygous null models (Lox -/-), the activity of LOX was reduced by up to 80%, and the phenotype of the lungs resembles those of patients with emphysema and dilated distal airways.^[16]

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.^[17]

Clinical significance

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.

In fact, recent research has shown overexpression of LOX as crucial to promoting tumor growth and metastasis in several cancers, including breast cancer,^[18] non-small cell lung cancer,^[19] and colorectal cancer.^[20]

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.^[21] 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.^[22]

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.^[23]

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.^[24]

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.^[25]

See also

• LOXL1
• LOXL2
• LOXL3
• LOXL4
• Menkes disease
• Occipital horn syndrome

Further reading

• Book: Csiszar K . Lysyl oxidases: a novel multifunctional amine oxidase family . 70 . 1–32 . 2001 . 11642359 . 10.1016/S0079-6603(01)70012-8 . 9780125400701 . Progress in Nucleic Acid Research and Molecular Biology .
• Kagan HM, Li W . Lysyl oxidase: properties, specificity, and biological roles inside and outside of the cell . Journal of Cellular Biochemistry . 88 . 4 . 660–72 . Mar 2003 . 12577300 . 10.1002/jcb.10413 . 23651213 .
• Svinarich DM, Twomey TA, Macauley SP, Krebs CJ, Yang TP, Krawetz SA . Characterization of the human lysyl oxidase gene locus . The Journal of Biological Chemistry . 267 . 20 . 14382–7 . Jul 1992 . 10.1016/S0021-9258(19)49723-8 . 1352776 . free .
• Mariani TJ, Trackman PC, Kagan HM, Eddy RL, Shows TB, Boyd CD, Deak SB . 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 . Jun 1992 . 1357535 . 10.1016/S0934-8832(11)80067-3 .
• Murawaki Y, Kusakabe Y, Hirayama C . Serum lysyl oxidase activity in chronic liver disease in comparison with serum levels of prolyl hydroxylase and laminin . Hepatology . 14 . 6 . 1167–73 . Dec 1991 . 1683640 . 10.1002/hep.1840140635 . 25820738 .
• Hämäläinen ER, Jones TA, Sheer D, Taskinen K, Pihlajaniemi T, Kivirikko KI . Molecular cloning of human lysyl oxidase and assignment of the gene to chromosome 5q23.3-31.2 . Genomics . 11 . 3 . 508–16 . Nov 1991 . 1685472 . 10.1016/0888-7543(91)90057-L .
• Konishi A, Iguchi H, Ochi J, Kinoshita R, Miura K, Uchino H . Increased lysyl oxidase activity in culture medium of nonparenchymal cells from fibrotic livers . Gastroenterology . 89 . 4 . 709–15 . Oct 1985 . 2863189 . 10.1016/0016-5085(85)90563-3.
• Kuivaniemi H, Ala-Kokko L, Kivirikko KI . Secretion of lysyl oxidase by cultured human skin fibroblasts and effects of monensin, nigericin, tunicamycin and colchicine . Biochimica et Biophysica Acta (BBA) - General Subjects . 883 . 2 . 326–34 . Sep 1986 . 2874833 . 10.1016/0304-4165(86)90325-9 .
• Reiser KM, Hennessy SM, Last JA . Analysis of age-associated changes in collagen crosslinking in the skin and lung in monkeys and rats . Biochimica et Biophysica Acta (BBA) - General Subjects . 926 . 3 . 339–48 . Dec 1987 . 3120785 . 10.1016/0304-4165(87)90220-0 .
• Järveläinen H, Halme T, Rönnemaa T . Effect of cortisol on the proliferation and protein synthesis of human aortic smooth muscle cells in culture . Acta Medica Scandinavica. Supplementum . 660 . 114–22 . 1982 . 6127904 . 10.1111/j.0954-6820.1982.tb00367.x.
• Kuivaniemi H, Savolainen ER, Kivirikko KI . Human placental lysyl oxidase. Purification, partial characterization, and preparation of two specific antisera to the enzyme . The Journal of Biological Chemistry . 259 . 11 . 6996–7002 . Jun 1984 . 10.1016/S0021-9258(17)39828-9 . 6144680 . free .
• Lien YH, Stern R, Fu JC, Siegel RC . Inhibition of collagen fibril formation in vitro and subsequent cross-linking by glucose . Science . 225 . 4669 . 1489–91 . Sep 1984 . 6147899 . 10.1126/science.6147899 . 1984Sci...225.1489L .
• Yasutake A, Powers JC . 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 . Jun 1981 . 6912069 . 10.1021/bi00516a002 .
• Kim Y, Boyd CD, Csiszar K . A new gene with sequence and structural similarity to the gene encoding human lysyl oxidase . The Journal of Biological Chemistry . 270 . 13 . 7176–82 . Mar 1995 . 7706256 . 10.1074/jbc.270.13.7176 . free .
• Hämäläinen ER, Kemppainen R, Pihlajaniemi T, Kivirikko KI . Structure of the human lysyl oxidase gene . Genomics . 17 . 3 . 544–8 . Sep 1993 . 7902322 . 10.1006/geno.1993.1369 .
• Forbes EG, Cronshaw AD, MacBeath JR, Hulmes DJ . Tyrosine-rich acidic matrix protein (TRAMP) is a tyrosine-sulphated and widely distributed protein of the extracellular matrix . FEBS Letters . 351 . 3 . 433–6 . Sep 1994 . 8082810 . 10.1016/0014-5793(94)00907-4 . 23360856 . free .
• Csiszar K, Mariani TJ, Gosin JS, Deak SB, Boyd CD . 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 . May 1993 . 8100215 . 10.1006/geno.1993.1203 .
• Vetter U, Weis MA, Mörike M, Eanes ED, Eyre DR . Collagen crosslinks and mineral crystallinity in bone of patients with osteogenesis imperfecta . Journal of Bone and Mineral Research . 8 . 2 . 133–7 . Feb 1993 . 8442432 . 10.1002/jbmr.5650080203 . 21904627 .
• Panchenko MV, Stetler-Stevenson WG, Trubetskoy OV, Gacheru SN, Kagan HM . Metalloproteinase activity secreted by fibrogenic cells in the processing of prolysyl oxidase. Potential role of procollagen C-proteinase . The Journal of Biological Chemistry . 271 . 12 . 7113–9 . Mar 1996 . 8636146 . 10.1074/jbc.271.12.7113 . free.
• Khakoo A, Thomas R, Trompeter R, Duffy P, Price R, Pope FM . Congenital cutis laxa and lysyl oxidase deficiency . Clinical Genetics . 51 . 2 . 109–14 . Feb 1997 . 9111998 . 10.1111/j.1399-0004.1997.tb02430.x . 36246895 .
• Smithen DA, Leung LM, Challinor M, Lawrence R, Tang H, Niculescu-Duvaz D, Pearce SP, Mcleary R, Lopes F, Aljarah M, Brown M, Johnson L, Thomson G, Marais R, Springer C . 6 . 2-Aminomethylene-5-sulfonylthiazole Inhibitors of Lysyl Oxidase (LOX) and LOXL2 Show Significant Efficacy in Delaying Tumor Growth . Journal of Medicinal Chemistry . 63 . 5 . 2308–2324 . March 2020 . 31430136 . 7073924 . 10.1021/acs.jmedchem.9b01112 .

Notes and References

1. Web site: Entrez Gene: LOX lysyl oxidase.
2. Hämäläinen ER, Jones TA, Sheer D, Taskinen K, Pihlajaniemi T, Kivirikko KI . Molecular cloning of human lysyl oxidase and assignment of the gene to chromosome 5q23.3-31.2 . Genomics . 11 . 3 . 508–16 . Nov 1991 . 1685472 . 10.1016/0888-7543(91)90057-L .
3. 10.1007/s00726-003-0012-1 . Recent Advances in the Analysis of Oxidized Proteins . 2003 . Requena . J. R. . Levine . R. L. . Stadtman . E. R. . Amino Acids . 25 . 3–4 . 221–226 . 14661085 . 28837698 .
4. Duff AP, Cohen AE, Ellis PJ, Kuchar JA, Langley DB, Shepard EM, Dooley DM, Freeman HC, Guss JM . The crystal structure of Pichia pastoris lysyl oxidase . Biochemistry . 42 . 51 . 15148–57 . Dec 2003 . 14690425 . 10.1021/bi035338v .
5. Gacheru SN, Trackman PC, Shah MA, O'Gara CY, Spacciapoli P, Greenaway FT, Kagan HM . Structural and catalytic properties of copper in lysyl oxidase . The Journal of Biological Chemistry . 265 . 31 . 19022–7 . Nov 1990 . 1977746 . 10.1016/0162-0134(89)84532-5 .
6. Thomassin L, Werneck CC, Broekelmann TJ, Gleyzal C, Hornstra IK, Mecham RP, Sommer P . The Pro-regions of lysyl oxidase and lysyl oxidase-like 1 are required for deposition onto elastic fibers . The Journal of Biological Chemistry . 280 . 52 . 42848–55 . Dec 2005 . 16251195 . 10.1074/jbc.M506832200 . free .
7. Kagan HM, Li W . Lysyl oxidase: properties, specificity, and biological roles inside and outside of the cell . Journal of Cellular Biochemistry . 88 . 4 . 660–72 . Mar 2003 . 12577300 . 10.1002/jcb.10413 . 23651213 .
8. Wang SX, Nakamura N, Mure M, Klinman JP, Sanders-Loehr J . Characterization of the Native Lysine Tyrosylquinone Cofactor in Lysyl Oxidase by Raman Spectroscopy . The Journal of Biological Chemistry . 272 . 46 . 28841–4 . Nov 1997 . 9360949 . 10.1074/jbc.272.46.28841 . free .
9. Bedell-Hogan D, Trackman P, Abrams W, Rosenbloom J, Kagan H . Oxidation, cross-linking, and insolubilization of recombinant tropoelastin by purified lysyl oxidase . The Journal of Biological Chemistry . 268 . 14 . 10345–50 . May 1993 . 10.1016/S0021-9258(18)82207-4 . 8098038 . free .
10. Akagawa M, Suyama K . Characterization of a model compound for the lysine tyrosylquinone cofactor of lysyl oxidase . Biochemical and Biophysical Research Communications . 281 . 1 . 193–9 . Feb 2001 . 11178979 . 10.1006/bbrc.2001.4315 .
11. Book: Alberts, Bruce . Molecular biology of the cell . Garland Science . New York . 2002 . 1099 . 978-0-8153-3218-3 .
12. Book: Csiszar K . Lysyl oxidases: a novel multifunctional amine oxidase family . 70 . 1–32 . 2001 . 11642359 . 10.1016/S0079-6603(01)70012-8 . 9780125400701 . Progress in Nucleic Acid Research and Molecular Biology .
13. Siegel RC, Fu JC, Uto N, Horiuchi K, Fujimoto D . Collagen cross-linking: lysyl oxidase dependent synthesis of pyridinoline in vitro: confirmation that pyridinoline is derived from collagen . Biochemical and Biophysical Research Communications . 108 . 4 . 1546–50 . Oct 1982 . 6129847 . 10.1016/S0006-291X(82)80083-1 .
14. Dawson DA, Rinaldi AC, Pöch G . Biochemical and toxicological evaluation of agent-cofactor reactivity as a mechanism of action for osteolathyrism . Toxicology . 177 . 2–3 . 267–84 . Aug 2002 . 12135629 . 10.1016/S0300-483X(02)00233-0 .
15. Wilmarth KR, Froines JR . In vitro and in vivo inhibition of lysyl oxidase by aminopropionitriles . Journal of Toxicology and Environmental Health . 37 . 3 . 411–23 . Nov 1992 . 1359158 . 10.1080/15287399209531680 . 1992JTEHA..37..411W .
16. Mäki JM, Sormunen R, Lippo S, Kaarteenaho-Wiik R, Soininen R, Myllyharju J . 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 . The American Journal of Pathology . 167 . 4 . 927–36 . Oct 2005 . 16192629 . 1603668 . 10.1016/S0002-9440(10)61183-2 .
17. Huang HY, Chen SZ, Zhang WT, Wang SS, Liu Y, Li X, Sun X, Li YM, Wen B, Lei QY, Tang QQ . Induction of epithelial-mesenchymal transition (EMT)-like response by BMP4 via up-regulation of lysyl oxidase is required for adipocyte lineage commitment . Stem Cell Research . 10 . 3 . 278–287 . May 2013 . 23395997 . 10.1016/j.scr.2012.12.005 .
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 . Critical role for lysyl oxidase in mesenchymal stem cell-driven breast cancer malignancy . Proceedings of the National Academy of Sciences of the United States of America . 109 . 43 . 17460–5 . Oct 2012 . 23033492 . 10.1073/pnas.1206653109 . 3491529. 2012PNAS..10917460E . free .
19. Shi W, Yang B, Li X, Sun S, Wang L, Jiao S . The effect of lysyl oxidase polymorphism on susceptibility and prognosis of nonsmall cell lung cancer . Tumour Biology . 33 . 6 . 2379–83 . Dec 2012 . 22948781 . 10.1007/s13277-012-0501-5 . 14633716 .
20. Baker AM, Cox TR, Bird D, Lang G, Murray GI, Sun XF, Southall SM, Wilson JR, Erler JT . The role of lysyl oxidase in SRC-dependent proliferation and metastasis of colorectal cancer . Journal of the National Cancer Institute . 103 . 5 . 407–24 . Mar 2011 . 21282564 . 10.1093/jnci/djq569 . free .
21. Erler JT, Giaccia AJ . Lysyl oxidase mediates hypoxic control of metastasis . Cancer Research . 66 . 21 . 10238–41 . Nov 2006 . 17079439 . 10.1158/0008-5472.CAN-06-3197 .
22. Erler JT, Bennewith KL, Cox TR, Lang G, Bird D, Koong A, Le QT, Giaccia AJ . Hypoxia-induced lysyl oxidase is a critical mediator of bone marrow cell recruitment to form the premetastatic niche . Cancer Cell . 15 . 1 . 35–44 . Jan 2009 . 19111879 . 3050620 . 10.1016/j.ccr.2008.11.012 .
23. Wilgus ML, Borczuk AC, Stoopler M, Ginsburg M, Gorenstein L, Sonett JR, Powell CA . Lysyl oxidase: a lung adenocarcinoma biomarker of invasion and survival . Cancer . 117 . 10 . 2186–91 . May 2011 . 21523732 . 10.1002/cncr.25768 . 25144943 .
24. Baker AM, Bird D, Welti JC, Gourlaouen M, Lang G, Murray GI, Reynolds AR, Cox TR, Erler JT . Lysyl oxidase plays a critical role in endothelial cell stimulation to drive tumor angiogenesis . Cancer Research . 73 . 2 . 583–94 . Jan 2013 . 23188504 . 10.1158/0008-5472.CAN-12-2447 . 3548904.
25. Rodríguez C, Rodríguez-Sinovas A, Martínez-González J . Lysyl oxidase as a potential therapeutic target . Drug News & Perspectives . 21 . 4 . 218–24 . May 2008 . 18560621 . 10.1358/dnp.2008.21.4.1213351 .