This family includes long-chain fatty acid (C12-C20) CoA synthetases, including an Arabidopsis gene At4g14070 that plays a role in activation and elongation of exogenous fatty acids. FACS catalyzes the formation of fatty acyl-CoA in a two-step reaction: the formation of a fatty acyl-AMP molecule as an intermediate, and the formation of a fatty acyl-CoA. Eukaryotes generally have multiple isoforms of LC-FACS genes with multiple splice variants. For example, nine genes are found in Arabidopsis and six genes are expressed in mammalian cells. Free fatty acids must be "activated" to their CoA thioesters before participating in most catabolic and anabolic reactions.
Jiyao W et al.(2023). "The conserved domain database in 2023.",