Mastoparan X has been isolated from the venom of Vespa xanthoptera. It has been suggested that mastoparan enhances the transport of Ca²⁺, Na⁺ and K⁺ ions through black membrane.
It is a G protein activator peptide that binds to Gi and Go. It also binds with high affinity to calmodulin (Kd~0.9 nM) and inhibits sarcoplasmic reticulum Ca2+-ATPase (Ki=4.4 mM).