Synthesis of ring labeled [ 1 ’ - 14 C ] - L - tyrosine Ryszard

The enzyme β-tyrosinase (tyrosine phenol lyase, EC 4.1.99.2) has been shown [8, 9, 15] to catalyze the decomposition of L-Tyr to phenol, pyruvate and ammonia. Under some conditions, this enzyme also participates in the reverse reaction leading to formation [10, 12, 13] of L-Tyr (Scheme 1). As a metabolism of L-Tyr is an important process of the living cells, the mechanism of the above reaction draws a special interest among biologists. This mutlistep reaction involving hydrogen transport and formation or rupture of bond between C1 ring and C3 side chain carbon atoms is still not clear. Some mechanistic questions can be answered by determining kinetic isotope effect, C KIE, [5, 6], for carbon atom in C1 ring position. For this purpose, the L-enantiomer form of specifically C-labeled isotopomer of tyrosine is needed. In the literature there are described several methods of synthesis of different isotopomers of tyrosine labeled with isotopes of carbon (C, C and C) using chemical and enzymatic routes. All these syntheses we described and discussed in our earlier paper [2] (see also references cited therein) dealing with obtaining of other C-labeled isotopomers of L-Tyr. This paper reports on the combined chemical and enzymatic synthesis of [1’-C]-L-Tyr, i.e., a specifically labeled isotopomer needed to perform such a kind of kinetic study. However, in this 6-step synthetic route the desired isotopomer, i. e., [1’-C]-L-Tyr was obtained Synthesis of ring labeled [1’-C]-L-tyrosine Ryszard Kański, Wojciech Augustyniak, Marianna Kańska