Dephosphorylation of tyrosine phosphorylated synthetic peptides by rat liver phosphotyrosine protein phosphatase isoenzymes

Abstract

Five phosphotyrosine-containing peptides have been synthesized by FMOC solid-phase peptide synthesis. These peptides correspond to the 4114 19 sequence of the Xenopus src oncogene, to the 1191 1220 sequence of the human EGF receptor precursor, to the 1146-1158 sequence of the human insulin receptor, to the 85(~865 sequence of the human/~-PDGF receptor, and to the 5-16 sequence of the erythrocyte human band 3. The peptides were used as substrates for activity assay of two isoforms (AcP1 and AcP2) of a low molecular weight cytosolic PTPase. The assay, performed in microtiter EIA plates using Malachite green to determine the released phosphate, was rapid, reproducible, and sensitive. Both PTPase isoforms were able to hydrolyze all synthesized peptides, though with different affinity and rate. The main kinetic parameters were compared and discussed with respect to the role of the two enzymes in the cell.

Inhibition of cellular response to platelet‐derived growth factor by low Mr phosphotyrosine protein phosphatase overexpression

“…This enzyme actively dephosphorylates phosphotyrosine-containing proteins and peptides [24], and belongs to the non-receptor-like subfamily. The reaction mechanism involves the formation of a cysteinylphosphate intermediate and the enzyme has the signature [25] of members of the PTPase family in its active site.…”

The Effect of ACP1-ADA1Genetic Interaction on Human Life Span

“…The phosphorylation of B3P tyrosines prevents the binding of several glycolytic enzymes, causing high glycolytic rates in erytrocytes (Harrison et al 1991;Low et al 1987). Furthermore, Stefani et al (1993) demonstrated that the phosphotyrosine of a syntethic peptide corresponding to the sequence 5-16 of the B3P is much more efficiently hydrolyzed by the ACP 1 f isozyme than s isozyme. Therefore, as the ACP 1 f amount is strongly related to ACP 1 activity (Dissing and Svensmark 1990;Stefani et al 1993) and its activity is enhanced by ADA 1 *2 (Lucarini et al 1989), it is conceivable that this fact may result in a significantly dephosphorylation of tyrosine residue of B3P, slowing glycolytic rates in erythrocytes.…”

“…These isozymes are expressed simultaneously in many tissues and they are characterized by different biological functions. ACP 1 f isozyme is the main responsible of the total ACP 1 activity (Dissing and Svensmark 1990;Fujimoto et al 1988;Stefani et al 1993). Since different effects on f and s isozymes activity result from modulation of ACP 1 enzymatic activity, C, CA and A phenotypes -characterized by lower concentrations of f isozymes -could be more susceptible to damage by oxidative events compared to the other phenotypes.…”

The genetics of signal transduction and the outcome of diagnostic tests in growth retardation

“…It is likely, therefore, that they perform different physiological functions. Indeed, Stefani et al (1993) have shown that S and F isoforms have somewhat different interactions with the insulin receptor. This may explain the differences observed in our study between high and low S ACP1 genotypes.…”