Kinetics of Phosphatase of Regenerating Liver-3 (PRL-3) Inhibition by Small-molecular Inhibitors1

Phosphatase of Regenerating Liver-3 (PRL-3) is a newly identified colorectal cancer metastasis-related protein, which is a 22 kDa non-classical protein tyrosine phosphatase with a C-terminal prenylation motif. In this study, the inhibition kinetics of protein tyrosine phosphatases (PTPs) by a fluorescent substrate, 6,8-difluoro-4-methylumbelliferyl phosphate (DiFMUP) was evaluated. PRL-3 exhibits classical Michaelis-Menten kinetics with a vmax value of 11.3 μmol · L−1 · min−1. Analysis of PRL-3 by a Michaelis-Menten plot and a double-reciprocal plot indicated that the inhibitor magnolol can cause Km to increase, but does not alter the vmax value, which suggests the competitive inhibition of PRL-3. At the same time, it was found that DiFMUP is a more sensitive substrate for PRL-3 than para-nitro-phenyl phosphate (pNPP) that is more frequently used at present. Furthermore, the method of screening for PTPs by the use of DiFMUP was developed, which studied the acceptance of DiFMUP by other PTPs.