3-hydroxyisobutyrate dehydrogenase

In enzymology, a 3-hydroxyisobutyrate dehydrogenase () also known as β-hydroxyisobutyrate dehydrogenase or 3-hydroxyisobutyrate dehydrogenase, mitochondrial (HIBADH) is an enzyme that in humans is encoded by the "HIBADH" gene.
3-Hydroxyisobutyrate dehydrogenase catalyzes the chemical reaction:
Thus, the two substrates of this enzyme are 3-hydroxy-2-methylpropanoate and NAD+, whereas its 3 products are 2-methyl-3-oxopropanoate, NADH, and H+.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 3-hydroxy-2-methylpropanoate:NAD+ oxidoreductase. This enzyme participates in valine, leucine and isoleucine degradation.
Function.
3-hydroxyisobutyrate dehydrogenase is a tetrameric mitochondrial enzyme that catalyzes the NAD+-dependent, reversible oxidation of 3-hydroxyisobutyrate, an intermediate of valine catabolism, to methylmalonate semialdehyde.
Structural studies.
As of late 2007, five structures have been solved for this class of enzymes, with PDB accession codes , , , , and .