The definition of tyrosinase

Tyrosinase is the key enzyme of melanin synthesis, which may be an important antigen of vitiligo autoimmunity. Recently found that some patients with vitiligo in the serum tyrosinase antibody, and clinical type and stage of vitiligo are closely related. Suggesting that the pathogenesis of autoimmune vitiligo and tyrosinase antibody levels, provide the basis for its immunotherapy. Tyrosinase antibodies can be used as an indicator of vitiligo activity.

Product Classification of Tyrosinase

Tyrosinase (TYR) is a 75kD copper-containing enzyme derived from embryonic nerve sheath cells and is a key enzyme in melanin metabolism and catecholamines. Spritz et al. Demonstrated that TYR is a copper-binding protein with copper A and copper B sites. The ionic copper-specific properties bind to human TYR, and copper binding at one site can promote copper binding at the other site. Histidine coordinates its binding at the copper B site. Proper folding of the polypeptide chains of TYR is critical for copper binding and its catalytic activity, and TYR mutations may disrupt copper binding to loss of its catalytic activity. Eye, skin albinism is due to TYR gene mutations caused by the disease TYR-positive patients with high incidence of pigmented skin lesions. Superoxide anion (O2-) can penetrate melanocytes (MC) into the cell, TYR through the use of O2-protection MC, from O2-cytotoxicity. In melanoma patients with melanoma cells (MMC) and MC in the antioxidant system imbalance, endogenous reactive oxygen production, the cells can not resist the endogenous superoxide attack. Vitiligo patients in the serum TYR antibody production, suggesting that the incidence of vitiligo and autoimmune.

Antigenicity of tyrosinase

The enzyme is a variety of autoimmune disorders of autoantigens, TYR as antigen must meet the following conditions: ① enzyme activity; ② immunogenicity; ③ can induce the identification of their own antibodies.

TYR can be used as the target antigen of autoantibody products; TYR has no cross-reaction with protease and so on, suggesting that anti-TYR antibody is specific for TYR, MC can express MHC Ⅱ Class of molecules, can be used as antigen presenting cells. Human MMC can secrete TYR, TYR antibodies in serum in patients with melanoma found in other patients with malignant tumors did not, suggesting that malignant melanoma can produce anti-TYR antibodies, TYR gene encoding antigen can be melanoma cell toxicity T Cells (CTL), indicating that the immune system can play a role in TYR.

Mammalian melanogenesis is regulated by multiple gene loci. There are many characteristic structural loci (B site, C site, S site and P site) in different loci and related proteins. Mammalian pigment cell regulation of a variety of genes, the most prominent feature of these genes is located in the C site (C-allbino locus), encoding TYR. The C-locus gene is 70 kb long, locates chromosome 7, and the human C-locus is 50 kb long, locating chromosome 11. Both mouse and human C locus genes contained five exons and four introns. TYR is a membrane glycoprotein that can be specifically expressed in MC. The brown locus gene encodes TRP-1 (gp75). The mouse B site gene is 18kb long, with 8 exons and 7 introns, locating chromosome 14. The human B site gene locates chromosome 9. TRP-1 can be expressed in MC and localized melanosomes, with tyrosine hydroxylase and dopa oxidase activity. The S-locus gene encodes TRP-2, and the mouse S-locus gene is located on chromosome 14, which is dopachrome isomerase. Mouse and human P site (Pmel-17 locus) gene encoding stablin protein, human and mouse P site gene locates chromosome 10, chromosome 12, involved in melatonin synthesis regulation of the terminal pathway.

TYR, gp75, TRP-2 are similar in structure, and their gene products have the following characteristics: (1) high homology (amino acid sequence 40%, similar 45%). ② molecular weight is almost the same. ③ tertiary structure has a highly conserved sequence of cysteine residues. ④ enzyme activity of copper binding sites. ⑤ contain transmembrane region.

TYR is a key enzyme in melanogenesis, and its known amino acid sequence contains a leader signal peptide and a transmifferent motif, which is consistent with the anchoring protein on the melanosomal membrane. HLA-A2 presented TYR antigens. Different cytotoxic T-lymphocyte clones identified the nine-peptide LLAVLYCLL with active motifs, which indicated that TYR expressed high homology in different individuals. The expression of TYR was higher than that of TRP-2, and the expression frequency was also higher than that of TRP-1. In addition to CD8 + T cells, human CD4 + T cells can also specifically recognize the TYR gene encoding the relevant antigen. TYR was detected in patients with melanoma, TYR is differentiation antigen on MMC. Can be used as active immunization good antigen target. TYR is restricted by both MHC-I and MHC-II, and the induced CD8 + T cells and CD4 + T cells can produce effective anti-tumor responses. TRP-1 in situ hybridization confirmed that the coding gene was located on chromosome 9 of human chromosome 9 and was an IgG antibody-recognizing antigen with DHI-2 carboxylate oxidase activity. Non-mutant TRP-1 antigen could be recognized by HLA-A31 specific CTL . Exogenous TRP-1 cDNA was expressed in MMC and the like. Gp100 is the MC / MMC-specific protein Pmel-17, immuno-electron microscopy confirmed gp100 mainly located in stage Ⅰ, Ⅱ melanoma membrane, widely expressed in human MMC (50%). The gp100 of HLA-A2 mMC can be recognized by autologous tumor-infiltrating lymphocytes (TIL). The recognition site is the decapeptide LLDGTATLRL (aa457-486). The decapeptide extracted from gp100 can induce TIL in vitro, and the combination of TIL cells and IL-2 can be used in HLA-A2 + melanoma patients to eliminate spontaneous melanoma metastasis kitchen.

Detection of tyrosinase antibody

TYR antibodies in serum in patients with vitiligo detected. Song et al. (1994) synthesized the human TYR with bacteria and detected the TYR antibody by immunoblotting. This method is relatively insensitive and can not be quantitatively detected. Baharav, etc. in 1996 using mushroom TYR, ELISA detection of TYR antibody, this method is sensitive, but the use of mushroom TYR and human TYR homology is low. In 1996, Xie et al. Used human MC extract as the source of TYR, immunoprecipitation and other detection of TYR antibody. Kemp, etc. in 1997 using radioimmunoassay (RIA) detection of TYR antibodies. Recently this method has been used to detect serum autoantibodies in patients with specific antibodies. This method can be sensitive to quantitative detection of antibodies.