This family consists of the amino termini of acyl-CoA thioester hydrolase and bile acid-CoA:amino acid N-acetyltransferase (BAAT) [1]. This region is not thought to contain the active site of either enzyme. Thioesterase isoforms have been identified in peroxisomes, cytoplasm and mitochondria, where they are thought to have distinct functions in lipid metabolism [2]. For example, in peroxisomes, the hydrolase acts on bile-CoA esters [1].

1: Characterization of an acyl-coA thioesterase that functions as a major regulator of peroxisomal lipid metabolism. Hunt MC, Solaas K, Kase BF, Alexson SE; J Biol Chem 2002;277:1128-1138. PMID:11673457

2: Peroxisome proliferator-induced long chain acyl-CoA thioesterases comprise a highly conserved novel multi-gene family involved in lipid metabolism. Hunt MC, Nousiainen SE, Huttunen MK, Orii KE, Svensson LT, Alexson SE; J Biol Chem 1999;274:34317-34326. PMID:10567408