Effects of the propeptide of group X secreted phospholipase A2 on substrate specificity and interfacial activity on phospholipid monolayers

► Mouse GX sPLA2 activity on phospholipid monolayers was measured for the first time. ► The substrate specificity of mGX was dependent on surface pressure. ► mGX acts on PE and PG but not on PC at surface pressure of biological membranes. ► Conditions can be found where the propeptide does not repress PLA2 activity. ► Structural modeling of mGX shows how the propeptide impairs access to the active site.