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Gene Review

tyr  -  tyrosinase

Xenopus laevis

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High impact information on Tyr

  • We sequenced ENaC in a family with Liddle syndrome and found a missense mutation in beta subunit which predicts substitution of Tyr by His at codon 618, 2 bp downstream from a missense mutation (P616L) that has been reported recently [1].
  • This enzyme, which has an apparent molecular mass of 100 kDa, performs a selective cleavage at the Xaa-Phe, Xaa-Leu, or Xaa-Ile bond (Xaa = Ser, Phe, Tyr, His, or Gly) of a number of peptide hormones, including atrial natriuretic factor, substance P, angiotensin II, bradykinin, somatostatin, neuromedins B and C, and litorin [2].
  • A mutation, which changes a highly conserved Cys to Tyr in transmembrane domain IS1, identifies a residue important for channel function not only in Drosophila muscle but also in mammalian cardiac channels [3].
  • MCT8 did not transport Leu, Phe, Trp, or Tyr [4].
  • Mutation of Ser-267 to large residues such as His, Cys, or Tyr resulted in inhibition of Gly-R function by ethanol [5].

Biological context of Tyr

  • This suggests the possibility that a dual-specificity membrane-associated protein kinase may catalyze phosphorylation of both Tyr 15 and Thr 14 [6].
  • The membrane-associated Tyr 15 and Thr 14 kinase activities behaved similarly during salt or detergent extraction and were similarly regulated during the cell cycle and by the checkpoint machinery that delays mitosis while DNA is being replicated [6].
  • Immunodepletion of MPM-2 antigens from cyclin-induced M-phase egg extract caused the inactivation of cdc2 kinase, which was accompanied by an inhibitory phosphorylation of p34cdc2 on Thr 14 and Tyr 15, indicating that at least one MPM-2 antigen is a positive regulator of p34cdc2 dephosphorylation [7].
  • Although considerable sequence variation exists in these TFIIIA zinc fingers, the Cys/His, Tyr/Phe and Leu residues are strictly conserved between X. laevis and X. borealis [8].
  • Uptake of Tyr, 3-I-Tyr and [(125)I]IMT followed Michaelis-Menten kinetics, with K(m) values of 29.0 +/- 5.1, 12.6 +/- 6.1 and 22.6 +/- 4.1 microM, respectively [9].

Anatomical context of Tyr

  • Metaphase-arrested, unfertilized shed oocytes of Xenopus laevis obtained after hormonal stimulation of the female are able to take up nucleosides (U, T) and amino acids (Ala, Gly, Glu, Gln, Tyr) [10].
  • These pigmented macrophages express mRNA for tyrosinase and also they show dopa oxidase activity; therefore they are able to synthesize melanins, as Kupffer cells do [11].
  • Reciprocal heterotopic and orthotopic trunk neural crest grafts have shown that the defect is intrinsic to the neural crest cells but is not due, in the case of melanophores, to a tyrosinase deficiency as revealed by the dopa reaction [12].

Associations of Tyr with chemical compounds

  • Mutationally converting this His to either Tyr or Trp restored lectin activity to the nonbinding ATB, emphasizing the contribution of an aromatic side chain in a functional 2 gamma subdomain galactose-binding site for members of this lectin family [13].
  • 4. Further mutations at different positions of the alpha subunit suggest the contribution of Pro and Tyr residues at positions 211 and 213 to quinacrine inhibition whereas mutations alpha I210A and alpha L212A did not have any effects [14].
  • Photoreactive peptide derivatives for the labelling of hormone receptors are usually prepared by inserting a chemically stable aryl azide or nitroaryl azide into a specific site of the molecule, such as an alpha or omega amino or carboxyl group, or into the side-chain of an Arg, Cys, His, Trp or Tyr [15].
  • Detergent-activated tyrosinase has a KM for dihydroxyphenylalanine of 6 X 10(-4) M and a KM for tyrosine of 4 X 10(-4) M [16].
  • The purified tyrosinase is a glycoprotein having a polypeptide Mr = 175,000 by NaDodSO4-polyacrylamide gel electrophoresis [16].

Regulatory relationships of Tyr


Other interactions of Tyr

  • Specifically, we have shown that a purified membrane fraction, in the absence of cytoplasm, can promote phosphorylation of cdc2 on both Thr 14 and Tyr 15 [6].

Analytical, diagnostic and therapeutic context of Tyr

  • Site-directed mutagenesis of residues in this region identified the residue Tyr379 of RBK1 as a crucial determinant of TEA sensitivity; substitution of Tyr in the equivalent positions of RBK2 (Val381) and RGK5 (His401) made these channels as sensitive to TEA as RBK1 [17].
  • Furthermore, microinjection of the mRNA into Xenopus oocytes results in the synthesis of active tyrosinase [18].


  1. Liddle disease caused by a missense mutation of beta subunit of the epithelial sodium channel gene. Tamura, H., Schild, L., Enomoto, N., Matsui, N., Marumo, F., Rossier, B.C. J. Clin. Invest. (1996) [Pubmed]
  2. A peptide-hormone-inactivating endopeptidase in Xenopus laevis skin secretion. Carvalho, K.M., Joudiou, C., Boussetta, H., Leseney, A.M., Cohen, P. Proc. Natl. Acad. Sci. U.S.A. (1992) [Pubmed]
  3. A mutation affecting dihydropyridine-sensitive current levels and activation kinetics in Drosophila muscle and mammalian heart calcium channels. Ren, D., Xu, H., Eberl, D.F., Chopra, M., Hall, L.M. J. Neurosci. (1998) [Pubmed]
  4. Identification of monocarboxylate transporter 8 as a specific thyroid hormone transporter. Friesema, E.C., Ganguly, S., Abdalla, A., Manning Fox, J.E., Halestrap, A.P., Visser, T.J. J. Biol. Chem. (2003) [Pubmed]
  5. Enhancement of glycine receptor function by ethanol is inversely correlated with molecular volume at position alpha267. Ye, Q., Koltchine, V.V., Mihic, S.J., Mascia, M.P., Wick, M.J., Finn, S.E., Harrison, N.L., Harris, R.A. J. Biol. Chem. (1998) [Pubmed]
  6. Membrane localization of the kinase which phosphorylates p34cdc2 on threonine 14. Kornbluth, S., Sebastian, B., Hunter, T., Newport, J. Mol. Biol. Cell (1994) [Pubmed]
  7. cdc25 is one of the MPM-2 antigens involved in the activation of maturation-promoting factor. Kuang, J., Ashorn, C.L., Gonzalez-Kuyvenhoven, M., Penkala, J.E. Mol. Biol. Cell (1994) [Pubmed]
  8. Sequence variation in transcription factor IIIA. Gaskins, C.J., Hanas, J.S. Nucleic Acids Res. (1990) [Pubmed]
  9. Characterization of 3-[125I]iodo-alpha-methyl-L-tyrosine transport via human L-type amino acid transporter 1. Shikano, N., Kanai, Y., Kawai, K., Ishikawa, N., Endou, H. Nucl. Med. Biol. (2003) [Pubmed]
  10. Transport of amino acids and nucleosides in metaphase-arrested unfertilized oocytes of Xenopus laevis. Jung, D., Richter, H.P. Cell Differ. (1984) [Pubmed]
  11. The spleen pigment cells in some amphibia. Scalia, M., Di Pietro, C., Poma, M., Ragusa, M., Sichel, G., Corsaro, C. Pigment Cell Res. (2004) [Pubmed]
  12. Genetic and experimental studies on a new pigment mutant in Xenopus laevis. Droin, A. J. Exp. Zool. (1992) [Pubmed]
  13. Restoration of lectin activity to an inactive abrin B chain by substitution and mutation of the 2 gamma subdomain. de Sousa, M., Roberts, L.M., Lord, J.M. Eur. J. Biochem. (1999) [Pubmed]
  14. Mutations in the M1 region of the nicotinic acetylcholine receptor alter the sensitivity to inhibition by quinacrine. Tamamizu, S., Todd, A.P., McNamee, M.G. Cell. Mol. Neurobiol. (1995) [Pubmed]
  15. Photoaffinity labelling of peptide hormone receptors. Eberle, A.N. J. Recept. Res. (1983) [Pubmed]
  16. A detergent-activated tyrosinase from Xenopus laevis. I. Purification and partial characterization. Wittenberg, C., Triplett, E.L. J. Biol. Chem. (1985) [Pubmed]
  17. Interaction between tetraethylammonium and amino acid residues in the pore of cloned voltage-dependent potassium channels. Kavanaugh, M.P., Varnum, M.D., Osborne, P.B., Christie, M.J., Busch, A.E., Adelman, J.P., North, R.A. J. Biol. Chem. (1991) [Pubmed]
  18. Isolation of tyrosinase-mRNA by affinity chromatography of polysomes. Kidson, S.H., Fabian, B.C. Biochim. Biophys. Acta (1985) [Pubmed]
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