TY - JOUR
T1 - (R,S)-Reticuline 7-O-methyltransferase and (R,S)-norcoclaurine 6-O-methyltransferase of Papaver somniferum - cDNA cloning and characterization of methyl transfer enzymes of alkaloid biosynthesis in opium poppy
AU - Ounaroon, Anan
AU - Decker, Gabriele
AU - Schmidt, Jürgen
AU - Lottspeich, Friedrich
AU - Kutchan, Toni M.
PY - 2003/12
Y1 - 2003/12
N2 - S-Adenosyl-L-methionine:(R,S)-reticuline 7-O-methyltransferase converts reticuline to laudanine in tetrahydrobenzylisoquinoline biosynthesis in the opium poppy Papaver somniferum. This enzyme activity has not yet been detected in plants. A proteomic analysis of P. somniferum latex identified a gel spot that contained a protein(s) whose partial amino acid sequences were homologous to those of plant O-methyltransferases. cDNA was amplified from P. somniferum RNA by reverse transcription PCR using primers based on these internal amino acid sequences. Recombinant protein was then expressed in Spodoptera frugiperda Sf9 cells in a baculovirus expression vector. Steady-state kinetic measurements with one heterologously expressed enzyme and mass spectrometric analysis of the enzymatic products suggested that this unusual enzyme is capable of carrying through sequential O-methylations on the isoquinoline and on the benzyl moiety of several substrates. The tetrahydrobenzylisoquinolines (R)-reticuline (4.2 sec-1 mM-1), (S)-reticuline (4.5 sec-1 mM -1), (R)-protosinomenine (1.7 sec-1 mM-1), and (R,S)-isoorientaline (1.4 sec-1 mM-1) as well as guaiacol (5.9 sec-1 mM-1) and isovanillic acid (1.2 sec -1 mM-1) are O-methylated by the enzyme with the ratio kcat/Km shown in parentheses. A P. somniferum cDNA encoding (R,S)-norcoclaurine 6-O-methyltransferase was similarly isolated and characterized. This enzyme was less permissive, methylating only (R,S)-norcoclaurine (7.4 sec-1 mM-1), (R)- norprotosinomenine (4.1 sec-1 mM-1), (S)- norprotosinomenine (4.0 sec-1 mM-1) and (R,S)-isoorientaline (1.0 sec-1 mM-1). A phylogenetic comparison of the amino acid sequences of these O-methyltransferases to those from 28 other plant species suggests that these enzymes group more closely to isoquinoline biosynthetic O-methyltransferases from Coptis japonica than to those from Thalictrum tuberosum that can O-methylate both alkaloid and phenylpropanoid substrates.
AB - S-Adenosyl-L-methionine:(R,S)-reticuline 7-O-methyltransferase converts reticuline to laudanine in tetrahydrobenzylisoquinoline biosynthesis in the opium poppy Papaver somniferum. This enzyme activity has not yet been detected in plants. A proteomic analysis of P. somniferum latex identified a gel spot that contained a protein(s) whose partial amino acid sequences were homologous to those of plant O-methyltransferases. cDNA was amplified from P. somniferum RNA by reverse transcription PCR using primers based on these internal amino acid sequences. Recombinant protein was then expressed in Spodoptera frugiperda Sf9 cells in a baculovirus expression vector. Steady-state kinetic measurements with one heterologously expressed enzyme and mass spectrometric analysis of the enzymatic products suggested that this unusual enzyme is capable of carrying through sequential O-methylations on the isoquinoline and on the benzyl moiety of several substrates. The tetrahydrobenzylisoquinolines (R)-reticuline (4.2 sec-1 mM-1), (S)-reticuline (4.5 sec-1 mM -1), (R)-protosinomenine (1.7 sec-1 mM-1), and (R,S)-isoorientaline (1.4 sec-1 mM-1) as well as guaiacol (5.9 sec-1 mM-1) and isovanillic acid (1.2 sec -1 mM-1) are O-methylated by the enzyme with the ratio kcat/Km shown in parentheses. A P. somniferum cDNA encoding (R,S)-norcoclaurine 6-O-methyltransferase was similarly isolated and characterized. This enzyme was less permissive, methylating only (R,S)-norcoclaurine (7.4 sec-1 mM-1), (R)- norprotosinomenine (4.1 sec-1 mM-1), (S)- norprotosinomenine (4.0 sec-1 mM-1) and (R,S)-isoorientaline (1.0 sec-1 mM-1). A phylogenetic comparison of the amino acid sequences of these O-methyltransferases to those from 28 other plant species suggests that these enzymes group more closely to isoquinoline biosynthetic O-methyltransferases from Coptis japonica than to those from Thalictrum tuberosum that can O-methylate both alkaloid and phenylpropanoid substrates.
KW - (R,S)-reticuline 7-O-methyltransferase
KW - Alkaloid biosynthesis
KW - Norcoclaurine 6-O-methyltransferase
KW - Opium poppy
KW - Papaver somniferum
UR - http://www.scopus.com/inward/record.url?scp=0347317979&partnerID=8YFLogxK
U2 - 10.1046/j.1365-313X.2003.01928.x
DO - 10.1046/j.1365-313X.2003.01928.x
M3 - Article
C2 - 14675446
AN - SCOPUS:0347317979
SN - 0960-7412
VL - 36
SP - 808
EP - 819
JO - Plant Journal
JF - Plant Journal
IS - 6
ER -