Macrophage migration inhibitory factor (MIF) - Its role in catecholamine metabolism

Macrophage migration inhibitory factor (MIF) was originally identified seve ral decades ago as a lymphokine-derived protein that inhibited monocyte mig ration. Recently, it has been reported that MIF has D-dopachrome tautomeras e, phenylpyruvate tautomerase and thiol protein oxidoreductase activities, although the physiological significance of those activities is not yet clea r. Here we show that MIF is able to catalyze the conversion of dopaminechro me and norepinephrinechrome, toxic quinone products of the neurotransmitter s dopamine and norepinephrine, respectively, to indole derivatives that may serve as precursors to neuromelanin. Since MIF is highly expressed in huma n brain, these observations raise the possibility that MIF participates in a detoxification pathway for catecholamine products and could therefore hav e an important role for neural tissues. The potential role of MIF in the fo rmation of neuromelanin from catecholamines is also an extremely interestin g possibility.