80943-22-2Relevant academic research and scientific papers
PURIFICATION AND CHARACTERIZATION OF THREE ISOFORMS OF S-ADENOSYL-L-METHIONINE: (R,S)-TETRAHYDROBENZYLISOQUINOLINE-N-METHYLTRANSFERASE FROM BERBERIS KOETINEANA CELL CULTURES
Frenzel, Thomas,Zenk, Meinhart H.
, p. 3491 - 3497 (1990)
Three distinctly different isoforms of S-adenosyl-L-methionine-(R,S)-tetrahydroisoquinoline-N-methyltransferases could be isolated from cell suspension cultures of Berberis koetineana.These isoforms were designated NMT-I, -II and -III.The three enzymes have different molecular weights (60-78 * 103), pH optima (6.8/7.4), kinetic properties and substrate specificities.NMT-I showed maximal activity with (R)-tetrahydropapaverine as substrate, NMT-II and -III were most active against (R)-coclaurine.The mixture of all three NMT's was immobilized on CH-Sepharose or CPG-10 glass beads.The enzymes under these conditions retained their properties and represent a useful tool for the preparative synthesis of isotopically labelled N-methylated benzylisoquinoline alkaloids.
THE HYDROXYLATION STEP IN THE BIOSYNTHETIC PATHWAY LEADING FROM NORCOCLAURINE TO RETICULINE
Loeffler, Susanne,Zenk, Meinhart H.
, p. 3499 - 3503 (2007/10/02)
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 (Mr 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.
