Pressure and temperature effects on formation of aminoacrylate intermediates of tyrosine phenol-lyase demonstrate reaction dynamics

The structures of aminoacrylate intermediates of wild-type, F448A mutant, and perdeuterated tyrosine phenol-lyase (TPL) formed from L-tyrosine, 3-F-L-tyrosine, S-ethyl-L-cysteine, and L-serine, with 4-hydroxpyridine bound, were determined by X-ray crystallography. All the aminoacrylate Schiff’s base structures in chain A are identical regardless of the substrate used to form them. The 4-hydroxypyridine is also in an identical location, except for F448A TPL, where it is displaced about 1 A due to the increased size of the active site. In chain B, we have found different complexes depending on the substrate. With wild-type TPL, L-tyrosine gave no density, 3-F-L-tyrosine gave a gem-diamine, and L-serine gave a gem-diamine, in chain B. S-Ethyl-L-cysteine formed an aminoacrylate in chain B with both wild-type and F448A TPL, but perdeuterated TPL with S-ethyl-L-cysteine formed a gem-diamine of aminoacrylate. The kinetics of aminoacrylate intermediate formation from L-tyrosine and S-ethyl-L-cysteine were followe...