Inhibition of protein tyrosine kinase by 5-S-GAD, a novel antibacterial substance from an insect

The effect of N-beta-alanyl-5-S-glutathionyl-dopa (5-S-GAD), a compound originally isolated from Sarcophaga peregrina (a flesh fly) as an antibacterial substance, on protein phosphorylation was examined using v-src-transformed NIH3T3 cell lysates, B-S-GAD was found to inhibit tyrosine phosphorylation of protein tyrosine kinase v-src, but not serine/threonine phosphorylation of protein kinase C. The potency of this compound was comparable to that of herbimycin A, Our results suggested that a substitution at position 5 of the catechol in B-S-GAD with the sulfur of cysteine is essential for 5-S-GAD to inhibit protein tyrosine kinase v-src. (C) 1997 Academic Press.