Yes, a dehydrogenase is an enzyme. More specifically, it belongs to a large class of enzymes called oxidoreductases, which catalyze oxidation-reduction reactions in living cells. Dehydrogenases work by removing hydrogen atoms from one molecule and transferring them to another, a process that drives many of the chemical reactions your body depends on for energy, detoxification, and basic cell function.
What Dehydrogenases Actually Do
Every dehydrogenase performs a version of the same basic task: it strips hydrogen (in the form of electrons and protons) from a substrate and hands it off to an acceptor molecule. This is a type of oxidation reaction. The substrate loses electrons and becomes oxidized, while the acceptor gains electrons and becomes reduced. This electron shuffle is how cells extract energy from food and channel it into usable forms.
To do this work, dehydrogenases rely on helper molecules called cofactors. The two most common are NAD+ (nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide). These cofactors act as electron taxis: they pick up hydrogen from the reaction, become “loaded” forms called NADH and FADH2, and carry those electrons to the cell’s energy-producing machinery. Without these cofactors, the enzyme can’t function.
Where They Fit in Enzyme Classification
Scientists classify enzymes using a numbering system maintained by the international Enzyme Commission (EC). The first digit tells you the broad class. Dehydrogenases fall under EC 1, the oxidoreductase class, which covers all enzymes that handle oxidation-reduction reactions. Within that class, dehydrogenases are distinguished by the fact that they specifically transfer hydrogen, rather than adding oxygen or performing other redox tasks. Oxidases, by contrast, catalyze reactions involving the addition of molecular oxygen. Reductases catalyze reactions where a substrate gains electrons. Dehydrogenases, oxidases, and reductases are all siblings under the oxidoreductase umbrella.
Key Dehydrogenases in Your Body
Alcohol Dehydrogenase
When you drink alcohol, your liver breaks it down using alcohol dehydrogenase (EC 1.1.1.1). This enzyme converts ethanol into acetaldehyde, a highly reactive and toxic byproduct. During the reaction, NAD+ picks up two electrons and becomes NADH. Acetaldehyde is what contributes to tissue damage from heavy drinking and likely plays a role in the unpleasant effects of a hangover. A second enzyme then converts acetaldehyde into a less harmful substance, but alcohol dehydrogenase handles the critical first step.
Lactate Dehydrogenase
Lactate dehydrogenase (LDH) catalyzes the final step of anaerobic glycolysis, the process your cells use to generate energy without oxygen. It converts pyruvate into lactate while simultaneously recycling NADH back into NAD+. That recycling step is essential because other reactions in glycolysis need a steady supply of NAD+ to keep running. When oxygen is available again, the reaction reverses: lactate converts back to pyruvate, which then enters the cell’s main energy cycle. This is why LDH is so active during intense exercise, when muscles temporarily outpace their oxygen supply.
LDH also shows up in blood tests. Normal levels generally fall between 135 and 225 units per liter for males and 135 to 214 U/L for females, though labs vary slightly. Elevated LDH in the blood signals that tissues somewhere in the body have been damaged, since cells release their LDH when they break down. The test can’t pinpoint which organ is affected, but it’s a useful flag for conditions ranging from liver disease to certain cancers.
Succinate Dehydrogenase
Succinate dehydrogenase holds a unique position in cellular energy production. It participates in both the citric acid cycle (where cells break down fuel molecules) and the electron transport chain (where cells convert that energy into ATP). In the citric acid cycle, it oxidizes succinate to fumarate. The electrons released during that reaction reduce FAD to FADH2, and those electrons then feed directly into the electron transport chain. No other enzyme in the citric acid cycle has this dual membership.
Malate Dehydrogenase
Malate dehydrogenase catalyzes another step in the citric acid cycle, converting malate to oxaloacetate while reducing NAD+ to NADH. The NADH produced eventually feeds into the electron transport chain to generate ATP. Oxaloacetate is a critical intermediate that keeps the citric acid cycle turning. A version of this enzyme also operates outside the mitochondria, helping shuttle reducing power into the cell’s energy-producing compartment through a system called the malate-aspartate shuttle.
When a Dehydrogenase Is Missing
The clearest example of what happens when a dehydrogenase doesn’t work properly is glucose-6-phosphate dehydrogenase (G6PD) deficiency, one of the most common enzyme disorders worldwide. G6PD normally protects red blood cells from oxidative damage. Without enough of it, red blood cells become vulnerable to destruction, a process called hemolysis.
People with G6PD deficiency are often fine under normal conditions, but certain triggers can set off a crisis. Infections, specific medications, and even fava beans can spike levels of reactive oxygen species in the blood, overwhelming the already-weakened red blood cells. When red blood cells break down faster than the body can replace them, the result is hemolytic anemia: pallor, jaundice (yellowing of the skin and eyes), dark urine, fatigue, shortness of breath, and a rapid heart rate. In newborns, G6PD deficiency is a significant cause of jaundice.
Why Dehydrogenases Matter Beyond Biology Class
Dehydrogenases aren’t just textbook enzymes. They sit at the core of how your body turns food into energy, processes alcohol, recovers from intense exercise, and protects cells from damage. When doctors order blood work that includes LDH levels, they’re using dehydrogenase activity as a window into tissue health. When geneticists screen for G6PD deficiency, they’re checking whether a single dehydrogenase is doing its job. And in biotechnology, alcohol dehydrogenases are used industrially to produce specific alcohols and chemical intermediates because of their ability to catalyze reactions in both directions with high precision.