Tryosine

Figure 1. Biosynthetic pathways for biogenic amines. In Drosophila and vertebrates decarboxylation of DOPA and 5-hydroxy-tryptophan is catalyzed by the same enzyme, DDC. In vertebrates this enzyme is called amino acid decarboxylase (AADC). Only vertebrates further metabolize dopamine to norepinephrine and epinephrine. TH, tryosine hydroxylase DDC, DOPA decarboxylase DBH, dopamine b-hydroxylase PNMT, phenylethanolamine N-methyltransferase. Tryp-OH tryptophan hydroxylase.

Bombick DW, Matsumura F. 1987. TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) causes an increase in protein tryosine kinase activities at an early stage of poisoning in vivo in rat hepatocyte membranes. Life Sci 41 429-436. 

Tyrosine is more fluorescent than tryptophan in solution, but when present in proteins, its fluorescence is weaker. This can be explained by the fact that the protein tertiary structure inhibits tryosine fluorescence. Also, energy transfer from tyrosines to tryptophan residues occurs in proteins inducing a total or important quenching of tyrosine fluorescence. This tyrosine — tryptophan energy transfer can be evidenced by nitration of tyrosine residues with tetranitromethane (TNM), a highly potent pulmonary carcinogen. Because TNM specifically nitrates tyrosine residues on proteins, the effects of TNM on the phosphorylation and dephosphorylation of tyrosine, and the subsequent effects on cell proliferation, can be investigated. 

E. Selective Cleavage of the Six Tryosine Peptide Bonds in Ribonuclease. 291... 

But the application of redox enzymes is also connected with intrinsic problems. The difficulty with redox enzymes in synthetic processes is based on the fact that this class of biocatalysts is dependent on freely dissociated (like NADH, NADPH, pteridin) or enzyme-bound (like FMN, FAD, thio-tryosine, PQQ, or cytochrome) cofactors, respectively, prosthetic groups (Fig. 1) in stoichiometric amounts to shuttle the redox equivalents from the enzyme to the substrate. 

Fernstrom, J. D., Wurtman, R. J., Hammarstrom-Wiklund, B., Rand, W. M., Munro, H. N., and Davidson, C. S. Diurnal variations in plasma concentrations of tryptophan, tryosine, and other neutral amino acids Effect of dietary protein intake, Am.. Clin. Nutr., 32, 1912, 1979. 

The crystal structures of several complexes of the metallo enzyme, carboxypeptidase A (CPA)(EC 3.4.17.1), have been examined in considerable detail. The structure of the complex with glycyl tryosine (Gly-Tyr) as been refined to 2.0 A resolution and reveals inter alia interactions between the amide carbonyl oxygen and the catalytically essential zinc, and between the amide nitrogen and the hydroxyl of tryosine-248 (Tyr-248)(Fig. 11). The proposed mechanisms for hydrolysis of peptide and ester bonds by CPA have relied heavily on these crystal structures, but a clear distinction between the possible roles of glutamate-270 (Glu-270) in nucleophilic attack either by general base catalysis (Fig. 11 A) or by covalent any hydride formation (Fig. IIB) remains a major unresolved problem. Indeed, it is not yet certain whether esters and amides are hydrolyzed by CPA via identical mechanisms. 

Leupeptin, trypsin inhibitor of actinomycetes, inhibited the esterase activity of Cls for arginine as well as tryosine esters, but chymostatin, a chymotrypsin-specific inhibitor of actinomycetes, was not inhibitory (Takahashi et a/., 1976b). 

Chemical Modification of Histidine and Tryosine Residues in Photosystem II 371... 

Aromatic amino acids also may serve as important precursors to fruit flavor. Some of the aromatic flavor compounds have been shown to come from tryosine and phenylalanine (Figure 4.7). Odors characterized as phenolic or spicy are formed via this pathway. 

Specific decarboxylases are availabe as exemplified by those for L-tryosine, L-lysine, L-glutamic acid, L-aspartic acid, or L-arginine. 

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