Photosensitive Switch Controls Enzyme Activity

A recent study explores the use of light-sensitive polymers as mechanical switches to control the catalytic activity of enzymes in vivo. The study was published December 16, 2002, in the online edition of the Proceedings of the National Academy of Sciences.

Researchers from the University of Washington (Seattle, USA) synthesized two light-sensitive polymers, DMAA and DMAAm. DMAA became hydrophilic and expanded when exposed to visible light, but became hydrophobic and contracted into a coil under UV light. DMMAm worked in reverse: under UV light it expanded, and under visible light it contracted.

The molecules were conjugated to endoglucanase, an enzyme that breaks down cellulose, at a specific point just outside the active site. Under the correct type of light the polymer shut down the enzyme activity by expanding to block the active site. The other type of light reversed the process, allowing access to the active site and restoring the enzyme's catalytic activity.

The authors of the study suggest that the true reversibility of a photosensitive switch would have many applications in a wide range of laboratory processes, including highly targeted drug therapies.



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