Tiopronin (2-mercaptopropionylglycine) has chemokinetic and chemotactic properties for polymorphonuclear leukocytes.

Tiopronin enhances migration of polymorphonuclear leukocytes (PMNs). The enhancing effect consists partly of a chemokinetic, and partly of a chemotactic effect. Intact sulfhydryl groups on the outer surface of the PMN plasma membrane are required for the enhanced locomotion: pretreatment of cells with the non-penetrating sulfhydryl reagent (5,5'-dithiobis(2-nitrobenzoic acid) completely abolishes the activating effect of tiopronin, but has only a moderate effect on activation by fMet-Leu-Phe. Pretreatment of PMNs with pertussis toxin inhibits tiopronin-induced enhancement of migration, suggesting that a pertussis toxin-sensitive G-protein is involved in the enhancing effect of tiopronin on PMN migration.