On the kinetics and mechanisms associated with covalent inactivation of protein tyrosine phosphatase 1b (ptp1b) by dietary phytochemicals and affinity labeling molecules

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Phytochemical are compounds that occur naturally in plants. These compounds are what give many foods their distinct color and flavor. There are five major types of phytochemicals; phenolic compounds, terepenes, betalains, glucosinolates, and organic acids. This work focused on a breakdown product of glucosinolates, isothiocyanates, which are found in Brassica, and are common in most diets. Isothiocyanates have a general structure of R-N=C=S, with an electron deficient carbon that is subject to nucleophilic attack by thiols to produce dithiocarbamates. This work investigated the inactivation of protein tyrosine phosphatase 1B by isothocyanates, and found that this occurs via a covalent, reversible mechanism. Affinity labels were originally used to elucidate the active site of many proteins. More recently however, much attention has been given to the use of an affinity label to covalently label a protein. It is with this technique of covalent attachment to our protein of interest that an exo-affinity labeling molecule was designed. The kinetics, stability, and mechanism of these molecules with protein tyrosine phosphatase 1B are evaluated here.