Cover Picture: Functionalized Bis-enol Acetates as Specific Molecular Probes for Esterases (ChemBioChem 18/2013)

The cover picture shows the sesquiterpene caulerpenyne (top left), which is found in high amounts in many green algae of Caulerpa spp. These algae form a biopolymer after wounding, sealing their giant cells (bottom left). Rapid polymer formation is initiated by esterases that activate caulerpenyne to a protein-reactive 1,4-dialdehyde. Inspired by this process, G. Pohnert et al. tailored synthetic caulerpenyne analogues containing the masked reactive group as well as a fluorescent tag. On , they explain how these probes are activated by lipolytic enzymes and specifically label esterases without labeling related lipases. MS-sequencing of labeled porcine liver esterase revealed that eight out of 35 lysines, exclusively located around the active site, are covalently modified after incubation with the probe (below right). Selectivity in complex samples was demonstrated by selective detection of esterases in crude Candida lipolytica protein extracts. This strategy, modeled after a natural process, now provides a conceptual new solution for an old problem in molecular probe design.