Hydrolyzes 3-hydroxyisobutyryl-CoA (HIBYL-CoA), a saline catabolite. Has high activity toward isobutyryl-CoA. Could be an isobutyryl-CoA dehydrogenase that functions in valine catabolism. Also hydrolyzes 3-hydroxypropanoyl-CoA. 3-hydroxy-2-methylpropanoyl-CoA + H2O = 3-hydroxy-2-methylpropanoate + CoA + H(+) Amino-acid degradation; L-valine degradation. Highly expressed in liver and kidney, also detected in heart, muscle and brain (at protein level). Not detected in lung. The disease is caused by variants affecting the gene represented in this entry. Belongs to the enoyl-CoA hydratase/isomerase family.