Alcohol dehydrogenase 1C (ADH1C), also known as class I alcohol dehydrogenase gamma subunit, is a cytosolic enzyme encoded by the ADH1C gene located on chromosome 4q23. This protein belongs to the medium-chain dehydrogenase/reductase (MDR) superfamily and functions as a homodimer or heterodimer with other ADH isoforms. ADH1C has a molecular weight of approximately 39.7 kDa and contains two zinc-binding sites: a catalytic site coordinating a catalytic zinc ion and a structural site coordinating a zinc ion essential for protein stability. The enzyme exhibits Michaelis-Menten kinetics with cofactor preference for NAD+ in oxidative reactions. ADH1C is primarily expressed in the liver but also maintains significant expression in brain tissue, making it relevant to neurodegeneration research.
Alcohol dehydrogenase 1C (ADH1C), also known as class I alcohol dehydrogenase gamma subunit, is a cytosolic enzyme encoded by the ADH1C gene located on chromosome 4q23. This protein belongs to the medium-chain dehydrogenase/reductase (MDR) superfamily and functions as a homodimer or heterodimer with other ADH isoforms. ADH1C has a molecular weight of approximately 39.7 kDa and contains two zinc-binding sites: a catalytic site coordinating a catalytic zinc ion and a structural site coordinating a zinc ion essential for protein stability. The enzyme exhibits Michaelis-Menten kinetics with cofactor preference for NAD+ in oxidative reactions. ADH1C is primarily expressed in the liver but also maintains significant expression in brain tissue, making it relevant to neurodegeneration research.
ADH1C catalyzes the reversible oxidation-reduction of primary and secondary alcohols to corresponding aldehydes and ketones, utilizing NAD+ as the electron acceptor. The enzyme demonstrates broad substrate specificity, accepting ethanol, retinol, various alicyclic alcohols, and endogenous substrates including polyamines and biogenic amines. In the brain, ADH1C participates in the metabolism of both exogenous and endogenous compounds with neurobiological significance. The protein's activity is subject to allosteric regulation by its substrates and products, and its expression levels are influenced by developmental stage, tissue type, and environmental factors including alcohol exposure. ADH1C exists as a polymorphic enzyme with two common variants (ADH1C1 and ADH1C2) arising from an amino acid substitution at position 271 (histidine or arginine), which affects catalytic efficiency and substrate affinity. These genetic variants influence enzymatic kinetics and may predispose individuals to differential responses to alcohol and other xenobiotics.
ADH1C contributes to neurodegeneration through multiple interconnected mechanisms. Excessive alcohol consumption, which generates toxic acetaldehyde through ADH1C-catalyzed ethanol oxidation, is a known risk factor for neurodegeneration and cognitive decline. Acetaldehyde accumulation induces neuronal oxidative stress, mitochondrial dysfunction, and protein aggregation. Additionally, ADH1C participates in the metabolism of endogenous substrates that accumulate during neuroinflammation, potentially contributing to neurotoxic conditions. In Alzheimer's disease pathology, aberrant alcohol metabolism and associated oxidative stress exacerbate amyloid-beta accumulation and tau phosphorylation. ADH1C-mediated production of reactive oxygen species (ROS) can amplify neuroinflammatory cascades and accelerate neuronal loss. The enzyme's role in retinoid metabolism is particularly significant; impaired retinoic acid signaling, downstream of ADH1C-catalyzed retinol oxidation, compromises neuroplasticity and cognitive function. Furthermore, ADH1C polymorphisms may influence individual susceptibility to alcohol-related neurodegeneration and potentially modify the trajectory of neurodegenerative disease progression.
ADH1C executes its function through a zinc-dependent catalytic mechanism involving hydride transfer to NAD+. The enzyme catalyzes the oxidation of ethanol to acetaldehyde, which is subsequently metabolized by aldehyde dehydrogenase (ALDH). Excessive ADH1C activity elevates intracellular acetaldehyde concentrations, which forms toxic adducts with proteins and DNA, triggering cellular stress responses. In mitochondria, ADH1C activity contributes to NAD+ depletion and altered redox states, compromising ATP production and calcium homeostasis. The enzyme's interaction with microsomal cytochrome P450 systems potentiates ROS generation through mixed-function oxidation. ADH1C also metabolizes endogenous lipid peroxidation products and participates in the detoxification of aldehydes generated during oxidative stress, creating bidirectional effects on cellular redox balance. The genetic variants of ADH1C possess differential kinetic parameters; ADH1C1 exhibits higher Vmax for ethanol oxidation compared to ADH1C2, producing variable rates of acetaldehyde generation and consequent neuronal toxicity.
ADH1C polymorphisms serve as genetic markers for alcohol susceptibility and alcohol-related neurodegeneration risk. Research indicates that individuals carrying ADH1C*1 alleles demonstrate increased vulnerability to alcohol-induced cognitive impairment and may face elevated Alzheimer's disease risk with chronic alcohol exposure. ADH1C represents a potential therapeutic target; selective inhibition could reduce acetaldehyde-mediated neuronal damage in alcohol use disorder. Emerging studies investigate ADH1C's contribution to age-related neurodegeneration independent of alcohol exposure, particularly through retinoid signaling dysfunction. Understanding ADH1C's role facilitates personalized risk assessment and development of targeted neuroprotective strategies.
AlphaFold DB provides a predicted structure for ADH1C / UniProt P00326 (model version 6): https://alphafold.ebi.ac.uk/entry/P00326.
AlphaFold reports a mean pLDDT confidence score of 98.12, indicating very high average confidence.
InterPro annotations highlight Alcohol dehydrogenase, zinc-type, conserved site conserved site (67-81); GroES-like superfamily homologous superfamily (3-185); Alcohol dehydrogenase-like, C-terminal domain (203-336).
PDB coordinates: https://alphafold.ebi.ac.uk/files/AF-P00326-F1-model_v6.pdb mmCIF coordinates: https://alphafold.ebi.ac.uk/files/AF-P00326-F1-model_v6.cif.
Use the prediction as structural context for target assessment; local low-pLDDT segments may reflect disorder, flexible linkers, or unresolved domain orientation rather than a stable fold.