Expression of enzymatically active cloned strictosidine synthase from the higher plant Rauvolfia serpentina in Escherichia coli.

The cDNA for strictosidine synthase, the enzyme catalyzing the stereospecific condensation of tryptamine with secologanin producing strictosidine, the key intermediate in indole alkaloid biosynthesis, has been expressed in an enzymatically active form in Escherichia coli. The cDNA trimmed of its 3'- and 5'-flanking regions was inserted into the vector pKK223-3 by addition of a synthetic adapter containing the ribosome binding site derived from the beta-galactosidase gene. Strictosidine synthase activity (138 nkat.l-1) could be measured in both whole bacteria and in bacterial protein extracts. Strictosidine synthase represents the first enzyme of plant secondary metabolism to be actively expressed in a microorganism.