Lysophospholipase II (LYPLA2, LPL-II, or LysoPLA II), also known as Acyl-protein thioesterase 2 (APT-2), belongs to the AB hydrolase 2 family. This enzyme has lysophospholipase activity and may hydrolyze fatty acids from S-acylated cysteine residues in proteins such as trimeric G alpha proteins or HRAS. Acyl-protein thioesterase 1 (APT-1) and Acyl-protein thioesterase 2 (APT-2) are cytosolic lysophospholipids hydrolyzing enzymes. The serum activity of APT-1 may play an important role in the determination of the concentration of des-acyl ghrelin in circulation, especially under septic inflammation. APT-2/LYPLA2 is expressed both in CHO-K1 and HeLa cells and its overexpression increased the deacylation rate of single acylated GAP-43 and affected the steady-state localization of diacylated GAP-43 and H-Ras. Thus, the results demonstrate that APT-2/LYPLA2 is the protein thioesterase involved in the acylation/deacylation cycle operating in GAP-43 subcellular distribution.