Towards Biocatalysts for Organosilane Chemistry

Biocatalytic reagents have assumed great importance in synthetic chemistry as they offer regio- and stereoselective routes to chiral intermediates and products, with the additional advantage of being environmentally benign and working at ambient temperatures and pressures. Transformations of a wide spectrum of substrates have been achieved using enzymes, which it is thought, are able to catalyze natural equivalents of all of the current reactions available to the contemporary organic chemist. Whilst the application of enzymes to the manipulation of classical "organic" atoms such as carbon, hydrogen, oxygen, phosphorus and sulphur is widespread, there has been scant reference to the transformation of silicon- containing substrates, or more specifically, enzymatic reactions at the silicon atom itself. This is surprising as silicon, the second most abundant atom in the earth`s crust, is the object of complex and varied biochemical reactions that in part contribute to the global silicon cycle. The manufacture of silicon-based materials typically requires high temperatures, high pressures or the use of caustic chemicals. By contrast, the biological production of amorphous silica, the simplest siloxane is accomplished under mild physiological conditions, producing a remarkable diversity of exquisitely architectures, whose nanoscale structural complexity operates on a scale currently beyond that of the limits of contemporary engineering. We aim to investigate the possibility of using the undiscovered yet undoubted ability of natural biocatalysts to catalyze reactions at the silicon atom, for synthetically useful Si-O and Si-C bond cleavages, with the aim of establishing a new field in applied biocatalysis research. A wide range of microorganisms representing a spectrum of microbial diversity and catabolic potential for the purpose of screening substrates for biotransformation is already available in the host group of Dr. Grogan. They have also synthesized the gene encoding silicatein alpha from Tethya aurantia, which is believed to play a significant role in the biosilicification process, and expressed in E. coli. Having in hand powerful biocatalysts from preliminary screens, we are keen to initiate subcellular studies of enzyme activities that will aim to identify the enzymatic processes responsible for the reactions. The host group is in an excellent position to start experiments in enzymology and structural biology to further investigate these biocatalysts, which would be of unprecedented activity.