Assessing the Tautomerase Activity of MIF Using L-Dopachrome

Macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine implicated in the pathogenesis of multiple acute and chronic inflammatory conditions, harbours diverse catalytic activity, notably the ability to tautomerize 2-carboxy-2,3-dihydroxyindole-5,6-quinone (L-dopachrome) to its dihydroxyindole derivative. While an endogenous substrate for this tautomerase activity is yet to be fully characterized, it is possible MIF enzymatic activity is important for numerous biological functions. As a result, assessing the tautomerase activity of MIF may serve as a useful screening tool for identifying small-molecule MIF inhibitors. This chapter details the use of a simple, cell-free, spectrophotometric assay for investigating the inhibitory potential of small-molecule compounds against the keto-enol tautomerase activity of MIF.