Related Experiment Video
Updated: Jul 10, 2026

Bio-layer Interferometry for Measuring Kinetics of Protein-protein Interactions and Allosteric Ligand Effects
Published on: February 18, 2014
Intrinsic deuterium isotope effects on benzylic hydroxylation by tyrosine hydroxylase
Patrick A Frantom1, Rongson Pongdee, Gary A Sulikowski
1Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA.
Abstract:
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.
Related Concept Videos
Cofactors and Coenzymes
Enzymes
Enzyme deficiencies can often translate into life-threatening diseases. For example, a genetic abnormality resulting in the deficiency of the enzyme G6PD...
Cofactors and Coenzymes
Introduction to Mechanisms of Enzyme Catalysis
Cofactors and Coenzymes
Cofactors can be metallic ions or organic molecules called coenzymes. These types of helper...
Introduction to Mechanisms of Enzyme Catalysis
![Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F55858.jpg&w=3840&q=50)
