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Conjugation Reaction of N-Acetyl Tyrosine with Adenosine Triphosphate (ATP) Catalyzed by Fe(II)/H2O2 System

Jian Zhang*

A conjugation reaction of N-acetyl tyrosine with adenosine triphosphate (ATP) was investigated by mass spectrometry in order to understand the mechanism to tyrosine phosphorylation in proteins. A reacting solution containing 10 mM of N-acetyl tyrosine, 6.4 mM of ATP disodium, 250 μM FeCl2, and 0.15% H2O2 was prepared in 500 μL of 20 mM ammonium bicarbonate (pH 7.4). The reactions were allowed to proceed for 48 h at room temperature followed by mass spectral analysis. It was found that this reaction was catalyzed by the Fe(II)/H2O2 system and the carboxyl terminus of N-acetyl tyrosine that bound to the ferrous ion. The reaction products seem to be the condensates of the phenolic group of tyrosine and the phosphate groups of ATP at a stoichiometry of 1:1 and higher which correspond to an m/z value of 736, 981 and 1248. The study also indicates that an additional step of ATP hydrolysis is needed to produce Phosphor-N-acetyl tyrosine (MW 303) from the conjugate. This reaction may be the precursor step of tyrosine phosphorylation in live organisms.