Microsomal oxidation is a set of reactions of the first phase of the biotransformation of xenobiotics and endogenous compounds catalyzed by enzyme systems of the membranes of the endoplasmic reticulum of hepatocytes with the participation of cytochrome P450 . With differential centrifugation, the endoplasmic reticulum appears in the microsomal fraction; therefore, these reactions are called microsomal, and the corresponding enzymes are called microsomal oxygenases.
The essence of the reactions is the hydroxylation of a substance of the RH type using one atom of the O 2 oxygen molecule, the second atom combines with hydrogen protons H + to form water. The proton donor is reduced NADPH + H + . Thus, the structure of the initial substance changes, and hence its properties, and they can both be inhibited and, vice versa, strengthened. Hydroxylation allows you to move the process of neutralization to the second phase - conjugation reactions, during which other molecules of endogenous origin will join the created functional group.
Reaction equation: RH + O 2 + NADPH + H + → ROH + H 2 O + NADP +
When some PAHs are hydroxylated, intermediate epoxides are formed (for example, epoxybenzanthracene ), which can easily cause carcinogenesis , apoptosis , and severe damage to hepatocytes, and subsequent necrosis , due to its high reactive, toxic, and carcinogenic abilities.