# Heme-Dependent Chemistry in Aromatic Oxidation

> **NIH NIH R01** · UNIVERSITY OF TEXAS SAN ANTONIO · 2022 · $323,534

## Abstract

Heme-Dependent Chemistry in Aromatic Oxidation
Abstract
Heme-containing enzymes are ubiquitous, contributing to various processes and catalyzing a vast array of
oxidative chemistries. Histidine-ligated heme enzymes, such as the heme-dependent aromatic oxygenase
(HDAO) superfamily, can use either molecular oxygen or hydrogen peroxide to oxidize their substrates. What
is currently not understood are the molecular factors that engender these enzymes with their respective
specificities, i.e., after generation of the critical active oxidant, how is a single reaction type catalyzed. The
answer to this question will broaden our fundamental understanding of enzyme catalysis, de novo enzyme
design, and protein engineering. This application focuses on the structural and mechanistic characterization of
three aromatic-oxidizing enzymes of the HDAO superfamily that are involved in natural product and
antimicrobial drug biosynthesis: TyrH, SfmD, and MarE. TyrH is a group of heme-dependent L-DOPA forming
monooxygenase in the biosynthesis of antibiotics with a pyrroline moiety. SfmD mediates the regioselective
hydroxylation of 3-methyl-L-tyrosine for synthesizing the core quinone structure of saframycin A. MarE forms
an oxindole structure for many compounds. These enzymes play important roles in the biosynthetic pathway of
secondary metabolites found in many biologically active natural products and pharmaceutical lead compounds.
Our primary goal is to understand the key factors that govern their hydroxylation mechanisms and their
differing strategies to form oxidizing intermediates with these enzymes. We have utilized a broad spectrum of
approaches to probe the intricate molecular details of these enzyme mechanisms using noncanonical amino
acids, substrate analogs, time-resolved UV-vis and EPR spectroscopies, kinetics, and isotope-labeling studies,
and we have been successful trapping on-pathway reaction intermediates in crystallo. The proposed work will
test our hypotheses regarding i) how the heme-based oxidant is generated, ii) how oxygen is directed to the
substrate, and iii) unravel the structural factors that affect catalysis. The outcome of the proposed studies is an
in-depth understanding of these three related catalytic systems to aid the development of scaffolds for rational
drug design and discovery processes.

## Key facts

- **NIH application ID:** 10540085
- **Project number:** 2R01GM108988-10
- **Recipient organization:** UNIVERSITY OF TEXAS SAN ANTONIO
- **Principal Investigator:** Aimin Liu
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $323,534
- **Award type:** 2
- **Project period:** 2014-08-01 → 2026-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10540085

## Citation

> US National Institutes of Health, RePORTER application 10540085, Heme-Dependent Chemistry in Aromatic Oxidation (2R01GM108988-10). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10540085. Licensed CC0.

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