FRET probes for measuring sphingolipid metabolizing enzyme activity.

Förster resonance energy transfer (FRET) probes are unique tools in biology, as they allow for a non-destructive monitoring of a certain state of a biomolecule or of an artificial substrate within living cells in real time. FRET substrates indicate their relative cleavage rate and thus the in situ activity of a given enzyme. In contrast to quenched probes or turn-on probes, one of the two separate signals of the FRET probes can be used as internal reference, which makes ratio-imaging and quantitation of cleavage events independent of cellular delivery possible. In this review, we describe the first examples of sphingolipid FRET probes in comparison to different alternative probes. Finally, we give an outlook on future probes and their potential application.