PLI binds directly phospholipase A2 in the presence or absence of calcium. Inhibitory activity of the PLI-A homotrimer is more specific than that of the PLI-B homotrimer. Homo- or heterotrimer; homotrimer of PLI-A chains, two PLI-A and one PLI-B chains, one PLI-A and two PLI-B chains, and homotrimer of PLI-B chains (with a ratio of 1:3:3:1). Secreted in plasma. Expressed by the liver. Belongs to the alpha-type phospholipase A2 inhibitor family.