TY - JOUR
T1 - Intrinsic deuterium isotope effects on benzylic hydroxylation by tyrosine hydroxylase
AU - Frantom, Patrick A.
AU - Pongdee, Rongson
AU - Sulikowski, Gary A.
AU - Fitzpatrick, Paul F.
PY - 2002/4/24
Y1 - 2002/4/24
N2 - Tyrosine hydroxylase (TyrH) is a mononuclear, non-heme iron monooxygenase that catalyzes the pterin-dependent hydroxylation of tyrosine to dihydroxyphenylalanine. When 4-methylphenylalanine is used as a substrate for TyrH, 4-hydroxymethylphenylalanine is one of the amino acid products. To examine the mechanism of benzylic hydroxylation, the products and their isotopic compositions were determined with 4-methylphenylalanines containing a mono-, di-, or trideuterated methyl group as substrates. Intrinsic primary and secondary deuterium isotope effects for benzylic hydroxylation of 9.6 ± 0.9 and 1.21 ± 0.08, respectively, were derived from the data. The magnitudes of these isotope effects are consistent with quantum mechanical tunneling of the hydrogen. The similarity of the effects to those seen for benzylic hydroxylation by other enzymes supports a mechanism where a high valence iron-oxo species, Fe(IV)=O, is the hydroxylating intermediate.
AB - Tyrosine hydroxylase (TyrH) is a mononuclear, non-heme iron monooxygenase that catalyzes the pterin-dependent hydroxylation of tyrosine to dihydroxyphenylalanine. When 4-methylphenylalanine is used as a substrate for TyrH, 4-hydroxymethylphenylalanine is one of the amino acid products. To examine the mechanism of benzylic hydroxylation, the products and their isotopic compositions were determined with 4-methylphenylalanines containing a mono-, di-, or trideuterated methyl group as substrates. Intrinsic primary and secondary deuterium isotope effects for benzylic hydroxylation of 9.6 ± 0.9 and 1.21 ± 0.08, respectively, were derived from the data. The magnitudes of these isotope effects are consistent with quantum mechanical tunneling of the hydrogen. The similarity of the effects to those seen for benzylic hydroxylation by other enzymes supports a mechanism where a high valence iron-oxo species, Fe(IV)=O, is the hydroxylating intermediate.
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U2 - 10.1021/ja025602s
DO - 10.1021/ja025602s
M3 - Article
C2 - 11960436
AN - SCOPUS:0037165727
VL - 124
SP - 4202
EP - 4203
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 16
ER -