Is involved in L-lysine degradation and provides glutaryl-CoA for biotin synthesis. Catalyzes the conversion of glutarate to glutaryl-CoA via the transfer of CoA from succinyl-CoA. glutarate + succinyl-CoA = glutaryl-CoA + succinate Amino-acid degradation. Cofactor biosynthesis; biotin biosynthesis. Inactivation of the gene leads to biotin auxotrophy. Belongs to the CoA-transferase III family.