Unit E: Signal-controlled catalysis

Our challenge

The initiation and direct control of a complex catalytic system by chemical or physical stimuli (light, voltage, pressure) is envisaged. This has not yet been achieved in chemocatalysis but is common in biocatalytic reactions in cells. Unit E aims at understanding the underlying basic concepts to pave the way for the controlled manipulation of catalytic systems in vivo.

Our approach

In this Unit, we will focus on

• Natural and artificial multicomponent catalytic systems which are coupled to transport processes across membranes (vectorial catalysis).
• Biochemical reaction cascades involving small molecules such as cyclic nucleotides or inositol compounds (enzymatic catalysis).
• Initiating the process via a natural photoreceptor attached to an enzyme (e.g., a cyclase or phosphodiesterase) that activates the production or decomposition of cyclic nucleotides. These messengers subsequently trigger a nucleotidedependent ion channel to generate changes of the transmembrane voltage.
• Artificial photodependent proton sources in membranes  will be used to generate pH/voltage gradients under light stimulation , triggering secondary catalytic processes via the activation of voltage/pHsensitive ion channels.
• Appropriate photoswitches acting as inhibitors only in one state will be employed to control the action of kinases generating inositol polyphosphates, a crucial step for unraveling this highly complex biocatalytic reaction sequence.

The ultimate goal is to transfer new approaches to biotechnological applications and to develop novel optogenetic tools in the neurosciences and cell biology.

Unit E shares the challenge of understanding the coupling of photoinduced and subsequent thermal reactions in Unit D, which in turn will support developing tailored photoswitches and caged compounds. Moreover, elucidating functional coupling between proteins represents a strong tie with Unit B and Unit C.