IDENTIFICATION AND CHARACTERIZATION OF PHOSPHOLIPASE-A2 INHIBITORY PROTEINS IN HUMAN MONONUCLEAR-CELLS

Calcium‐dependent phospholipid binding and phospholipase A2 inhibitory proteins were isolated from human mononuclear cells. Lipocortins I and H were present whereas lipocortin IV (endonexin I) was not. The other proteins were purified to homogeneity and shown to have molecular masses of 35, 36, 32 and 73 kDa. The 36‐kDa and 73‐kDa proteins are related, the smaller appears to be part of the larger. The 73‐kDa protein is related to the 67‐kDa calelectrin and to lipocortin VI; the 32‐kDa protein is different from endonexin I but related to chromobindin 7 and to lipocortin V. The 35‐kDa protein has been identified by tryptic peptide sequencing as lipocortin III. All these proteins inhibit phospholipase A2 activity in vitro the three smaller ones inhibit the [3H]arachidonic acid release from prelabelled monocytes induced of by the calcium iononphore A23187 in a dose‐dependent manner. Copyright © 1990, Wiley Blackwell. All rights reserved