Substrate specificity of protein tyrosine phosphatase: differential behavior of SHP-1 and SHP-2 towards signal regulation protein SIRPalpha1

The substrate specificity of catalytic domains and the activation of full length protein tyrosine phosphatases, SHP-1 and SHP-2 have been investigated using synthetic phosphotyrosyl peptides derived from SIPRalpha1. We found that the catalytic domains of SHP-1 and SHP-2 exhibit different substrate specificity towards a longer trideca-peptide pY(469+3) ((-7)RPEDTLTpYADLDM(+5)) and not to the shorter decapeptide pY(469) ((-5)EDTLTpYADLD(+4)), the former being the substrate of SHP-2 only. Furthermore, the activation of full-length SHP-1 and not the SHP-2 by the deca/trideca-peptides suggested SIRPalpha 1 to be possibly acting as both an upstream activator and a substrate for SHP-1, and merely as the downstream substrate for SHP-2 in signaling events.