Oxidation Reaction Classification

What happens during Hydroxylation?

Adds OH to either an aliphatic carbon or aromatic ring carbon

What happens during epoxidation?

Adds oxygen across a double bond → forms epoxide (3-membered ring)

What happens during N-dealkylation?

Removes alkyl group from nitrogen → forms amine + aldehyde/ketone

• has hemiaminal intermediate → functional group with a hydroxyl and an amine bonded to the same carbon atom

What happens during O-dealkylation?

Removes alkyl group from oxygen → forms alcohol/phenol + aldehyde/ketone

• has hemiacetal intermediate → functional group with a hydroxyl and one alkoxy (—OR) group attached to the same carbon atom

What happens during Oxidative dehalogenation?

Removes halogen (Cl, F, etc.) and replaces with oxygen

What happens during S-Dealkylation?

Removes an alkyl group from sulfur (S) → forms a thiol (–SH) + aldehyde/ketone

What happens during Ester Cleavage (CYP-Catalyzed)?

breaks ester bond → forms alcohol intermediate → carboxylic acid

What happens during oxidative deamination (CYP) ?

Removes NH₂ group → forms ketone or aldehyde + ammonia (NH3)

What happens during oxidative deamination (MAO) ?

Removes NH₂ group → forms ketone or aldehyde + ammonia (NH3)

ALSO creates H2O2, hydrogen peroxide → reactive/damaging byproduct

How does MAO in oxidative deamination work?

The amine becomes an aldehyde

Nitrogen leaves as ammonia

Oxygen gets reduced → forms hydrogen peroxide (H₂O₂)

• H₂O₂ is reactive/damaging, so cells often use catalase to break it down.

What happens in oxidative desulfurization?

Replaces sulfur (S) with oxygen (O)

• thiol → alcohol or similar

What happens in N-Oxidation (CYP and FMO)?

Adds oxygen to nitrogen → forms N-oxide (N—O)

FMO Used for tertiary N (3*)

What happens in S-Oxidation?

Adds oxygen to sulfur → forms sulfoxide or sulfone (S=O or O=S=O)

Occurs mostly with FMO

What happens in Beta-Oxidation?

Breaks down fatty acids by removing 2-carbon units (acetyl-CoA) from the β-carbon

• Occurs in mitochondria → fuels ATP production

• coenzyme A required

What happens in purine / pyrimidine oxidation?

Adds –OH to the purine/pyrimidine → generates reactive oxygen species (ROS)

What enzymes are needed for purine / pyrimidine oxidation?

Xanthine oxidase

or

Aldehyde oxidase

What happens during Alcohol Oxidation?

Alcohol → aldehyde (or ketone)

What enzymes and cofactors required for alcohol oxidation?

Alcohol dehydrogenase → ADH

Cofactor → NAD+

Is a reversible reaction

What happens during Aldehyde oxidation?

Aldehyde → carboxylic acid

What enzymes and cofactors required aldehyde oxidation?

Aldehyde dehydrogenase → ALDH

Cofactors → NAD+ and H2O

What happens during Dihydrodiol Dehydrogenase?

Dihydrodiol → catechol → auto-oxidizes → ortho-quinone

What enzymes are required for dihydrodiol dehydrogenase?

Enzyme → DDH or dihydrodiol dehydrogenase

Cofactors → NADP+, gets turned into NADPH

What can happen to ortho-quinones?

Undergo redox cycling → repeatedly reduced/oxidized → generates ROS

What reactions are CYP catalyzed?

Hydroxylation

Epoxidation

N-dealkylation

O-dealkylation

Oxidative dehalogenation

Ester Cleavage

Oxidative desulfurization

What reactions are non-CYP catalyzed?

Beta Oxidation → Coenzyme A

Purine / Pyrimidine Oxidation → Xanthine oxidase / Aldehyde Oxidase

Alcohol oxidation → ADH
Aldehyde oxidation → ALDH

Dihydrodiol dehydrogenase → DDH

What reactions are occurs with multiple enzymes?

Oxidative deamination → CYP and MAO

N-oxidation → CYP and FMO for tertiary amines

S-oxidation → FMO mostly, but CYP can happen

What is needed for the enzyme MAO?

O2

H2O

What is needed for the enzyme FMO?

NADPH

O2

H+