Catalyzes the succinyl-CoA-dependent conversion of glutarate to glutaryl-CoA. Can use different dicarboxylic acids as CoA acceptors, the preferred ones are glutarate, succinate, adipate, and 3-hydroxymethylglutarate. 3-hydroxy-3-methylglutarate + succinyl-CoA = (3S)-hydroxy-3-methylglutaryl-CoA + succinate Highly expressed in kidney. Intermediate expression in liver, skeletal muscle and pancreas. Little to no expression detected in other tissues examined. The disease is caused by variants affecting the gene represented in this entry. Belongs to the CoA-transferase III family. It is uncertain whether Met-1 or Met-8 is the initiator.