Tyrosine hydrogenation

K. J. Willis and A. G. Szabo, The fluorescence decay kinetics of tyrosinate and tyrosine hydrogen bonded complexes, J. Phys. Chem. 95, 1585-1589 (1991). 

Hydroxyl Serine, threonine, tyrosine Hydrogen bonding, acid-base catalysis... 

As a p hydroxy derivative of phenylalanine tyrosine has properties similar to those of phenylalanine plus the ability to engage m hydrogen bonding via its —OH group Asparagine and glutamine are not amines they are amides The side chains of both O... 

In order for the cyclooxygenase to function, a source of hydroperoxide (R—O—O—H) appears to be required. The hydroperoxide oxidizes a heme prosthetic group at the peroxidase active site of PGH synthase. This in turn leads to the oxidation of a tyrosine residue producing a tyrosine radical which is apparendy involved in the abstraction of the 13-pro-(5)-hydrogen of AA (25). The cyclooxygenase is inactivated during catalysis by the nonproductive breakdown of an active enzyme intermediate. This suicide inactivation occurs, on average, every 1400 catalytic turnovers. 

S,N-Ditrityl-L-cysteine diethylamine selt L-Tyrosine lower alkyl ester L-lsoleucine lower alkyl ester Benzyl-L-proline hydrochloride L-Leucine lower alkyl ester Ammonia Hydrogen chloride Glycine lower alkyl ester... 

Hydrogen peroxide (H202) exhibits insulin-like activity in isolated cells. Like that of vanadate, this effect is thought to be mediated by inhibition of protein-tyrosine phosphatases. 

In a related series of experiments, the amino group and/or the carboxylic acid group of tyrosine were replaced by hydrogen atoms. The corresponding tyrosine derivatives are 3-(4 -hydroxyphenyl)-propionic acid, commonly known as desaminotyrosine (Dat), and tyramine (Tym) (structures 3-5). 

Isoflavones have been implicated in goiter induction. Soybean extracts inhibit reactions catalyzed by thyroid peroxidase (TPO), essential to the synthesis of thyroid hormones (Divi et al., 1997). Genistein and daidzein (at about 1-10 p,M of IC50) may act as alternative substrates for tyrosine iodination (Divi et al., 1997). Furthermore, genistein and daidzein have also been shown to cause the irreversible inactivation of TPO in the presence of hydrogen peroxide. Genistein also inhibits thyroxine synthesis in the presence of iodinated... 

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