3-hydroxyisobutyrate dehydrogenase catalyzes the NAD-dependent, reversible oxidation of 3-hydroxbutyrate to methylmalonate. In eukaryotes, it is a homodimeric mitochondrial protein involved in valine catabolism. In Pseudomonas aeruginosa (gene mmsB), it is involved in the distal valine metabolic pathway.

The sequence of 3-hydroxyisobutyrate dehydrogenase from eukaryotic and prokaryotic sources show that this enzyme has been well conserved throughout evolution.

As a signature pattern, it was selected a highly conserved glycine-rich region located at the proteins' N-terminus. This region is probably involved in binding NAD.
Reference