1.5.1.31 additional information recombinant coexpression of enzyme STOX and six other enzymes, including the three membrane-bound enzymes: the flavin-dependent oxidase berberine bridge enzyme, the cytochrome P450 canadine synthase, and a cytochrome P450 reductase, in Saccharomyces cerevisiae results in protoberberine alkaloid production from a simple benzylisoquinoline alkaloid precursor rac-norlaudanosoline. Improvement of flux through the pathway, by methods including enzyme variant screening, genetic copy number variation, and culture optimization, leading to an over 70fold increase in canadine titer up to 1.8 mg/l 743234