Dehydrogenase Crystals as Catalysts in Organic Synthesis

Enzyme microcrystals (less than 100 um) grown from aqueous solution and cross-linked witha bifunctional agent such as glutaraldehyde exhibit remarkable characteristics that are superior to bothsoluble and conventionally immobilized enzymes. Such cross-linked enzyme crystals (CLECs) remainactive in environments that are otherwise incompatible with enzyme function, including prolongedexposure to high temperatures, extremes of pH, near-anhydrous organic solvents and aqueous-organicsolvent mixtures. CLECs are also remarkably stable against autolysis and exogenous proteasedegradation. This unique set of properties makes CLECs extremely useful in organic synthesis in generaland in the synthesis of optically pure compounds in particular. The authors have demonstrated thesynthetic utility of CLECs in the synthesis of aspartase, catalyzed by thermolysis and in the synthesisof optically pure compounds, catalyzed by lipase from Candida rugosa. In this Phase I study, CLECs ofa cofactor-dependent enzyme alcohol dehydrogenase (ADH) from two different sources will beinvestigated to demonstrate the feasibility of using CLECs of cofactor-dependent enzymes for practicalstereoselective synthesis. ADH was chosen because it is one of the most studied, as well as useful andversatile cofactor-dependent enzymes for stereoselective organic synthesis.