The catalytic role of aspartic acid-92 in a human dual-specific protein-tyrosine-phosphatase

Enzyme assay reveals that compared to native human dual-specific protein-tyrosine, phosphatase, the aspartic acid-92-aspargine (D92N) mutant enzyme exhibits 100-fold less activity. Presence of protonated native enzyme D92 is necessary for catalytic activity. In the rate limiting step, the D92 residue protonates the phenolate ion by functioning as a general acid. D92 facilitates the hydrolysis of the phosphoenzyme intermediate by acting as a general base.