2 is a human gene. This page covers the gene's normal function, disease associations, expression patterns, and key research findings relevant to neurodegeneration.
ALDH2 (Aldehyde Dehydrogenase 2) encodes a mitochondrial enzyme that catalyzes the oxidation of toxic aldehydes to their corresponding carboxylic acids. This NAD+-dependent enzyme plays a critical role in cellular detoxification, metabolizing harmful aldehydes generated during lipid peroxidation, alcohol metabolism, and oxidative stress. ALDH2 is particularly important in tissues with high metabolic activity and exposure to oxidative stress, including the heart, liver, and brain. The enzyme activity is essential for protecting cells from aldehyde-induced damage that contributes to neurodegeneration, cardiovascular disease, and cancer.
¶ Protein Structure and Function
ALDH2 is a homotetrameric enzyme localized to the mitochondrial matrix. Each subunit contains:
- Catalytic domain: Contains the active site with catalytic cysteine (Cys302)
- NAD+ binding domain: Rossmann-fold structure for cofactor binding
- Oligomerization interface: Mediates tetramer formation
ALDH2 catalyzes the oxidation of aldehydes in a two-step process:
- Thiohemiacetal formation: The aldehyde reacts with the catalytic cysteine (Cys302)
- Hydride transfer: NAD+ accepts a hydride, forming NADH and the acyl-enzyme intermediate
- Hydrolysis: Water hydrolyzes the thioester, releasing the carboxylic acid product
ALDH2 metabolizes numerous toxic aldehydes:
- 4-Hydroxynonenal (4-HNE): Major lipid peroxidation product
- Malondialdehyde (MDA): Another lipid peroxidation by-product
- Acetaldehyde: Ethanol metabolism product
- Acetylaldehyde: Formed during dopamine oxidation
- Propionaldehyde: Environmental exposure
¶ Expression and Localization
ALDH2 is expressed at high levels in:
- Brain: Hippocampus, cerebral cortex, substantia nigra, cerebellum
- Heart: Cardiac myocytes
- Liver: Hepatocytes
- Kidney: Renal tubular cells
- Skeletal muscle: Muscle fibers
In neurons, ALDH2 is concentrated in:
- Mitochondria (primary location)
- Synaptic terminals
- Axonal compartments
- Postsynaptic densities
ALDH2 is a critical player in protecting neurons from aldehyde-induced toxicity:
- ALDH2 activity is significantly decreased in AD brains, particularly in hippocampus and cortex
- Accumulation of toxic aldehydes (4-HNE, MDA) contributes to neuronal death
- 4-HNE promotes tau hyperphosphorylation and amyloid-β toxicity
- The enzyme protects against lipid peroxidation-induced synaptic dysfunction
- ALDH2 rs671 (Glu504Lys) polymorphism increases AD risk in East Asian populations
- ALDH2 metabolizes acetaldehyde produced during dopamine oxidation
- The enzyme protects dopaminergic neurons from toxic aldehydes
- ALDH2 activity is reduced in the substantia nigra of PD patients
- The rs671 variant is associated with increased PD risk
- 4-HNE promotes α-synuclein aggregation and toxicity
- Amyotrophic Lateral Sclerosis (ALS): ALDH2 protects motor neurons from oxidative damage
- Huntington's Disease: ALDH2 deficiency exacerbates mutant huntingtin toxicity
- Stroke and Brain Injury: ALDH2 limits damage from ischemic/reperfusion injury
- rs671 (Glu504Lys): Common in East Asians, reduces ALDH2 activity by ~40-80%
- Associated with increased AD and PD risk
- Affects alcohol tolerance and cardiovascular disease risk
- rs4646776: Associated with aldehyde metabolism efficiency
- rs2236672: Influences enzyme expression levels
- ALDH2 activity in CSF reflects mitochondrial health in neurodegenerative diseases
- 4-HNE-ALDH2 adducts in brain tissue indicate oxidative stress burden
- Genetic testing for ALDH2 variants can inform disease risk
- ALDH2 activators: Alda-1 and related compounds enhance enzyme activity
- Gene therapy: Viral vector delivery of ALDH2 protects neurons in models
- Small molecule approaches: Enhancing ALDH2 expression or activity
Key protein interactions and pathways:
| Partner |
Interaction Type |
Function |
| 4-HNE |
Substrate |
Lipid peroxidation product, neurotoxic |
| NAD+ |
Cofactor |
Electron acceptor in oxidation |
| SOD2 |
Antioxidant |
Co-protection against oxidative stress |
| PGC-1α |
Transcriptional |
Mitochondrial biogenesis regulation |
| PARK2/Parkin |
Mitophagy |
Mitochondrial quality control |
| SIRT3 |
Deacetylase |
Modulates ALDH2 activity |