What Is 3-mercaptopyruvate sulfurtransferase

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Last updated: April 15, 2026

Quick Answer: 3-Mercaptopyruvate sulfurtransferase (3-MST) is an enzyme encoded by the MPST gene in humans, first identified in 1964, that catalyzes the transfer of sulfur from 3-mercaptopyruvate to produce hydrogen sulfide (H₂S), a key gasotransmitter involved in cellular signaling and redox regulation.

Key Facts

3-MST was first isolated in 1964 from bovine liver by A. Maruyama and colleagues
The human MPST gene is located on chromosome 22q13.1
3-MST contributes to up to 70% of endogenous H₂S production in certain brain regions
The enzyme has a molecular weight of approximately 33 kDa
3-MST activity is highest in the brain, kidneys, and vascular endothelium

Overview

3-Mercaptopyruvate sulfurtransferase (3-MST) is a mitochondrial and cytosolic enzyme that plays a critical role in sulfur metabolism and the production of hydrogen sulfide (H₂S), a gasotransmitter with regulatory functions in the nervous, cardiovascular, and immune systems. It operates primarily through the cysteine catabolic pathway, converting 3-mercaptopyruvate (3-MP) into pyruvate and transferring a sulfur atom to form H₂S.

Unlike other H₂S-producing enzymes such as cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE), 3-MST functions independently of vitamin B6-dependent reactions in certain contexts. Its discovery in mammalian tissues has expanded understanding of alternative H₂S biosynthesis pathways, particularly in neuroprotection and oxidative stress modulation.

Discovery year: 3-MST was first isolated in 1964 from bovine liver, marking a milestone in enzymology and sulfur biochemistry.
Gene location: The human MPST gene resides on chromosome 22q13.1, encoding a protein of 307 amino acids.
Enzyme class: It belongs to the sulfurtransferase family, specifically transferring sulfur from 3-mercaptopyruvate to nucleophilic acceptors.
Subcellular localization: Found in both mitochondria and cytosol, enabling dual roles in energy metabolism and redox signaling.
H₂S production: Contributes to up to 70% of endogenous hydrogen sulfide in specific brain regions under physiological conditions.

How It Works

3-MST catalyzes a two-step reaction involving the transsulfuration of 3-mercaptopyruvate, derived from cysteine aminotransferase activity, to generate reactive sulfur species. The enzyme’s mechanism involves a conserved cysteine residue (Cys247 in humans) that forms a persulfide intermediate, which then donates sulfur to produce H₂S or other sulfur-containing molecules.

Substrate:3-Mercaptopyruvate (3-MP) is the primary substrate, generated from cysteine and α-ketoglutarate via cysteine aminotransferase in a PLP-dependent reaction.
Catalytic residue:Cysteine 247 is essential for activity, forming a persulfide intermediate during the sulfur transfer process.
Reaction product: The enzyme releases pyruvate and transfers sulfur to thiophilic acceptors, ultimately yielding hydrogen sulfide (H₂S).
pH optimum: 3-MST exhibits maximal activity at pH 8.0–8.5, indicating alkaline preference in enzymatic function.
Inhibitors:Carbonyl cyanide m-chlorophenylhydrazone (CCCP) and aminooxyacetic acid (AOAA) inhibit 3-MST activity in experimental models.
Co-localization: Often co-expressed with cysteine aminotransferase in neurons, supporting localized H₂S synthesis in the central nervous system.

Comparison at a Glance

Comparing 3-MST with other H₂S-producing enzymes highlights functional and structural distinctions in gasotransmitter regulation.

Enzyme	Primary Substrate	H₂S Yield	Tissue Distribution	Key Inhibitor
3-MST	3-Mercaptopyruvate	Moderate to high	Brain, kidneys, endothelium	AOAA
CBS	Cysteine, homocysteine	High	Liver, brain, pancreas	AOAA, B6 deficiency
CSE	Cysteine	High	Vascular tissue, liver	Propargylglycine
MPST gene product	Identical to 3-MST	Same as 3-MST	Ubiquitous but enriched in CNS	Same as 3-MST
DAO pathway	D-amino acids	Low	Peripheral tissues	Not well established

The table illustrates that while CBS and CSE produce higher H₂S levels in peripheral tissues, 3-MST is particularly significant in neural environments where its activity supports antioxidant defense and neuromodulation. Its unique substrate specificity and subcellular distribution make it a key player in localized sulfur signaling.

Why It Matters

Understanding 3-MST is crucial for advancing research in neurodegenerative diseases, cardiovascular health, and inflammatory conditions due to its role in H₂S-mediated cytoprotection. Its ability to modulate oxidative stress and mitochondrial function positions it as a therapeutic target.

Neuroprotection: 3-MST-derived H₂S reduces neuronal damage in models of Alzheimer’s and Parkinson’s disease by scavenging reactive oxygen species.
Cardiovascular function: Regulates vascular tone by promoting smooth muscle relaxation through KATP channel activation.
Anti-inflammatory effects: Suppresses NF-κB signaling, reducing pro-inflammatory cytokine production in macrophages.
Mitochondrial support: Enhances ATP synthesis and protects against electron transport chain dysfunction under hypoxic conditions.
Drug development: Inhibitors and activators of 3-MST are being explored for treating chronic kidney disease and ischemia-reperfusion injury.
Genetic implications: Mutations in MPST are linked to altered stress responses and may influence susceptibility to psychiatric disorders.

As research progresses, 3-MST continues to emerge as a vital component of cellular redox homeostasis, offering promising avenues for targeted therapies in multiple disease states.