Pyruvate as a fluorescence quencher: a new spectroscopic assay for pyruvate reactions.

Pyruvate ion, which is biologically ubiquitous and participates in many metabolic reactions, was found to be an effective quencher of fluorescence. Compared to other negatively charged quenchers such as I-, pyruvate is not toxic to proteins. By adding an inert, long-lived fluorophore to systems transacting pyruvate, it is possible to estimate activity by measuring the time course of the change in pyruvate quenching of the fluorophore. The procedure is illustrated by measuring the myosin subfragment-1 ATPase activity with a high sensitivity.