Aldehyde dehydrogenase

Aldehyde dehydrogenases (EC 1.2.1.3) are a group of enzymes that catalyse the oxidation of aldehydes. They convert aldehydes (R–C(=O)–H) to carboxylic acids (R–C(=O)–O–H). The oxygen comes from a water molecule. To date, nineteen ALDH genes have been identified within the human genome. These genes participate in a wide variety of biological processes including the detoxification of exogenously and endogenously generated aldehydes.Tetramer of aldehyde dehydrogenase 2 with a space filling model of NAD+ in each active site.The active site of a human mitochondrial aldehyde dehydrogenase 2. Cys302 and Glu268 interact with the aldehyde substrate. The NAD+ is held in place by multiple residues (shown as wires or sticks).The active site of the K487E mutant aldehyde dehydrogenase 2 with a space filling model of NAD+ in the active site. The amino acid Glu349 is highlighted. Aldehyde dehydrogenases (EC 1.2.1.3) are a group of enzymes that catalyse the oxidation of aldehydes. They convert aldehydes (R–C(=O)–H) to carboxylic acids (R–C(=O)–O–H). The oxygen comes from a water molecule. To date, nineteen ALDH genes have been identified within the human genome. These genes participate in a wide variety of biological processes including the detoxification of exogenously and endogenously generated aldehydes. Aldehyde dehydrogenase is a polymorphic enzyme responsible for the oxidation of aldehydes to carboxylic acids, which leave the liver and are metabolized by the body’s muscle and heart. There are three different classes of these enzymes in mammals: class 1 (low Km, cytosolic), class 2 (low Km, mitochondrial), and class 3 (high Km, such as those expressed in tumors, stomach, and cornea). In all three classes, constitutive and inducible forms exist. ALDH1 and ALDH2 are the most important enzymes for aldehyde oxidation, and both are tetrameric enzymes composed of 54 kDa subunits. These enzymes are found in many tissues of the body but are at the highest concentration in the liver. The active site of the aldehyde dehydrogenase enzyme is largely conserved throughout the different classes of the enzyme and, although the number of amino acids present in a subunit can change, the overall function of the site changes little. The active site binds to one molecule of an aldehyde and one of either NAD+ or NADP+ that functions as a cofactor. A cysteine and a glutamate will interact with the aldehyde substrate. Many other residues will interact with the NAD(P)+ to hold it in place. A magnesium may be used to help the enzyme function, although the amount it helps the enzyme can vary between different classes of aldehydes.