THE HYDROXYLATION STEP IN THE BIOSYNTHETIC PATHWAY LEADING FROM NORCOCLAURINE TO RETICULINE

Article abstract of DOI:10.1016/0031-9422(90)85264-G

A phenolase was purified to homogeneity (488-fold) from cell suspension cultures of Berberis stolonifera.This enzyme in the presence of O2 and ascorbate introduces a meta-hydroxyl group into tyrosine, tyramine, coclaurine, and N-methylcoclaurine.No other hydroxylating activity directed towards N-methylcoclaurine could be found in this tissue.The enzyme (M_r 60 * 10³) is probably a dimer with two identical subunits, it has a pH optimum at 6.0 and a temperature optimum in the range of 20-30 deg C.Evidence is presented that this enzyme catalyses two separate reactions in the formation of reticuline, namely the hydroxylation of tyrosine (tyramine) to DOPA (dopamine) and the 3'-hydroxylation of N-methylcoclaurine to 3'-hydroxy-N-methylcoclaurine, the penultimate intermediate to reticuline.