8VMK

A crystal structure of heme-dependent tyrosine hydroxylase complexed with a substrate analog, 3-(4-hydroxyphenyl)propionic acid

8VMK の概要

• エントリーDOI: 10.2210/pdb8vmk/pdb
• 分子名称: Heme-dependent L-tyrosine hydroxylase, HYDROXYPHENYL PROPIONIC ACID, PROTOPORPHYRIN IX CONTAINING FE, ... (5 entities in total)
• 機能のキーワード: tyrosine hydroxylase, heme enzyme, binary complex, oxidoreductase, oxidoreductase-inhibitor complex, oxidoreductase/inhibitor
• 由来する生物種: Streptomyces sclerotialus
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 71055.79

構造登録者

Wang, Y.,Traore, E.,Liu, A. (登録日: 2024-01-13, 公開日: 2025-08-27, 最終更新日: 2026-03-25)

主引用文献

Traore, E.S.,Wang, Y.,Griffith, W.P.,Liu, A.
Substrate Analogs Implicate a Free Radical Pathway in Tyrosine Hydroxylase Catalysis.
Acs Catalysis, 15:18270-18281, 2025

PubMed Abstract: Heme-dependent tyrosine hydroxylases (TyrH) are critical enzymes in catecholamine biosynthesis, yet the role of the substrate's -amino group in their monooxygenation mechanism has been unclear. Using 3-(4-hydroxyphenyl)propionic acid (HPPA), an l-tyrosine analog lacking the -amino group, we observed a distinct dimerization pathway that competes with the expected hydroxylation reaction. Several lines of evidence confirm that this process originates from a radical intermediate. First, the formation of this (HPPA) dimer is selectively inhibited by a free radical scavenger. Second, O-labeling experiments show phenolic oxygen scrambling, indicating a disruption of substrate aromaticity during catalysis. Finally, EPR spectroscopy using nitrosobenzene as a substrate analog revealed a substrate-based free radical. This mechanistic divergence clarifies the role of the -amino group. Its absence in HPPA creates a kinetic bottleneck for the final O atom transfer step, allowing a fraction of the substrate radical to form the off-pathway dimer. Thus, the native substrate's -amino group acts as a crucial kinetic modulator, ensuring the rapid and efficient commitment of the substrate radical to productive hydroxylation. These results collectively establish a peroxidase-like free radical pathway for TyrH and reveal the nonessential yet significant role the amino group plays in controlling reaction outcomes.

PubMed: 41737883
DOI: 10.1021/acscatal.5c05776

実験手法

X-RAY DIFFRACTION (1.56 Å)