ME2 Human
Description
Introduction to ME2 Human
ME2 Human (Malic Enzyme 2, Mitochondrial) is a NAD(P)+-dependent mitochondrial enzyme encoded by the ME2 gene. It catalyzes the oxidative decarboxylation of L-malate to pyruvate, generating NAD(P)H and CO₂, and plays a critical role in cellular energy metabolism, redox balance, and mitochondrial respiration . ME2 is expressed in metabolically active tissues and tumor cells, where it supports rapid proliferation by linking the tricarboxylic acid (TCA) cycle with glycolysis and lipid biosynthesis .
Quaternary Organization
ME2 functions as a homotetramer (≈240 kDa), with each monomer (≈64.4 kDa) composed of 573 amino acids . Cryo-EM studies reveal two conformational states:
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Open form: Exposed active site (inactive state).
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Closed form: Substrate-bound, solvent-protected active site (active state) .
Key Domains and Binding Sites
| Domain/Region | Function |
|---|---|
| Domain A (helical) | Allosteric regulation |
| Domain B/C | Catalytic core for malate decarboxylation |
| Domain D | Tetramer stabilization |
| Fumarate-binding site | Allosteric activation site at the dimer interface |
| Exo-site | Binds nucleotides (NAD+/ATP) at the tetramer interface |
ME2’s activity is regulated by fumarate (activator) and ATP (inhibitor) .
Metabolic Functions
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Pyruvate/NADH Production: Converts malate to pyruvate, supplying substrates for the TCA cycle and oxidative phosphorylation .
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NAD+/NADH Ratio Modulation: Overexpression lowers NAD+/NADH (pro-reductive state), while inhibition elevates it (pro-oxidative state) .
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ATP Synthesis: Supports mitochondrial respiration; ME2 knockdown reduces ATP levels by 40% .
Pathological Implications
Small-Molecule Inhibitors
Mechanistic Insights
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MDSA/EA: Reduce pyruvate/NADH production, elevate NAD+/NADH ratios, and impair oxidative phosphorylation .
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NPD389: Suppresses ME2 activity in cancer cells, inducing ROS accumulation and apoptosis .
ME2 Knockdown/Overexpression Studies
| Model System | Findings |
|---|---|
| HEK293T (ME2 overexpression) | ↑ Pyruvate (+60%), ↓ NAD+/NADH ratio (−50%) . |
| ME2-silenced cells | ↓ ATP (−40%), ↑ ROS (+300%), impaired proliferation . |
Inhibitor Efficacy
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MDSA/EA: Reduce pyruvate by 30–50% in non-cancerous cells (HEK293T, HFL-1) and H1299 lung carcinoma .
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NPD389: Inhibits ME2 with 10-fold higher potency than parent compound NPD387 .
Clinical and Research Applications
Product Specs
KMTSPLEKYIYIMGIQERNEKLFYRILQDDIESLMPIVYTPTVGLACSQYGHIFRRPKGL
FISISDRGHVRSIVDNWPENHVKAVVVTDGERILGLGDLGVYGMGIPVGKLCLYTAC
AGIRPDRCLPVCIDVGTDNIALLKDPFYMGLYQKRDRTQQYDDLIDEFMKAITDRYG
RNTLIQFEDFGNHNAFRFLRKYREKYCTFNDDIQGTAAVALAGLLAAQKVISKPISEH
KILFLGAGEAALGIANLIVMSMVENGLSEQEAQKKIWMFDKYGLLVKGRKAKIDSYQ
EPFTHSAPESIPDTFEDAVNILKPSTIIGVAGAGRLFTPDVIRAMASINERPVIFALSNPT
AQAECTAEEAYTLTEGRCLFASGSPFGPVKLTDGRVFTPGQGNNVYIFPGVALAVILC
NTRHISDSVFLEAAKALTSQLTDEELAQGRLYPPLANIQEVSINIAIKVTEYLYANKMAF
RYPEPEDKAKYVKERTWRSEYDSLLPDVYEWPESASSPPVITEHHHHHH.
Product Science Overview
ME2 is a homotetrameric protein, meaning it consists of four identical subunits. Each subunit is a non-glycosylated polypeptide chain containing 573 amino acids, resulting in a total molecular mass of approximately 64.4 kDa . The enzyme is characterized by its ability to bind NAD+ (nicotinamide adenine dinucleotide) and catalyze the conversion of malate to pyruvate, releasing carbon dioxide in the process .
The reaction catalyzed by ME2 is as follows:
This reaction is essential for maintaining the balance of NAD+/NADH in the mitochondria and plays a significant role in energy production and metabolic regulation.
Recombinant human ME2 is typically produced in Escherichia coli (E. coli). The recombinant protein is expressed as a single polypeptide chain with a His-tag at the C-terminus to facilitate purification . The protein is then purified using proprietary chromatographic techniques to achieve a purity of over 95%, as determined by SDS-PAGE and HPLC .
Recombinant ME2 is widely used in biochemical and physiological studies to understand its role in metabolism and its potential implications in various diseases. It is also used in drug discovery and development to screen for inhibitors or activators of the enzyme.
The recombinant ME2 protein is typically lyophilized from a concentrated solution in PBS (phosphate-buffered saline) at pH 7.4 and stored at temperatures ranging from -20°C to -70°C . After reconstitution, the protein can be stored at 2-8°C for up to one month or at -20°C to -70°C for long-term storage. It is important to avoid repeated freeze-thaw cycles to maintain the protein’s stability and activity .
