Biotransformations using plant cells, organ cultures and enzyme systems: current trends and future prospects.

Plants are valuable sources of a variety of chemicals including drugs, flavours, pigments and agrochemicals. Some of the biochemical reactions occurring in plant cells are complex and cannot be achieved by synthetic routes. In vitro plant cell and organ cultures and plant enzymes act as suitable biocatalysts to perform these complex reactions. A wide variety of chemical compounds including aromatics, steroids, alkaloids, coumarins and terpenoids can undergo biotransformations using plant cells, organ cultures and enzymes. The biocatalyst-mediated reactions are regiospecific and stereospecific. Reaction types include oxidations, reductions, hydroxylations, methylations, acetylations, isomerizations, glycosylations and esterfications. Genetic manipulation approaches to biotransformation offer great potential to express heterologous genes and to clone and overexpress genes for key enzymes. Biotransformation efficiencies can further be improved using molecular techniques involving site-directed mutagenesis and gene manipulation for substrate specificity.