PAF-AH catalyzes the hydrolysis of the acetyl group at the sn-2 position of PAF to yield lyso-PAF and acetate, thereby inactivating PAF. Two main types of PAF-AH have been characterized, namely the secreted -i.e., plasma) and intracellular enzymes. These are encoded on individual genes and share only 41% homology at the amino acid level. Plasma PAF-AH is a 45.4 kDa enzyme which is associated with the low-density lipoprotein fraction of plasma.