Comparative transcript and alkaloid profiling in Papaver species identifies a short chain dehydrogenase/reductase involved in morphine biosynthesis.
Plants of the order Ranunculales, especially members of the species Papaver, accumulate a large variety of benzylisoquinoline alkaloids with about 2500 structures, but only the opium poppy (Papaver somniferum) and Papaver setigerum are able to produce the analgesic and narcotic morphine and the antitussive codeine. In this study, we investigated the molecular basis for this exceptional biosynthetic capability by comparison of alkaloid profiles with gene expression profiles between 16 different Papaver species. Out of 2000 expressed sequence tags obtained from P. somniferum, 69 show increased expression in morphinan alkaloid-containing species. One of these cDNAs, exhibiting an expression pattern very similar to previously isolated cDNAs coding for enzymes in benzylisoquinoline biosynthesis, showed the highest amino acid identity to reductases in menthol biosynthesis. After overexpression, the protein encoded by this cDNA reduced the keto group of salutaridine yielding salutaridinol, an intermediate in morphine biosynthesis. The stereoisomer 7-epi-salutaridinol was not formed. Based on its similarities to a previously purified protein from P. somniferum with respect to the high substrate specificity, molecular mass and kinetic data, the recombinant protein was identified as salutaridine reductase (SalR; EC 1.1.1.248). Unlike codeinone reductase, an enzyme acting later in the pathway that catalyses the reduction of a keto group and which belongs to the family of the aldo-keto reductases, the cDNA identified in this study as SalR belongs to the family of short chain dehydrogenases/reductases and is related to reductases in monoterpene metabolism.
Ziegler
Jörg
J
Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle, Germany. jzeigler@ipb-halle.de
Voigtländer
Susan
S
Schmidt
Jürgen
J
Kramell
Robert
R
Miersch
Otto
O
Ammer
Christian
C
Gesell
Andreas
A
Kutchan
Toni M
TM
D000470:Alkaloids / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D016000:Cluster Analysis; D018076:DNA, Complementary / Q000737:chemistry; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling; D008969:Molecular Sequence Data; D009019:Morphinans / Q000737:chemistry / Q000378:metabolism; D009020:Morphine / Q000737:chemistry / Q000378:metabolism*; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010207:Papaver / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D020539:Sequence Analysis, Protein; D013379:Substrate Specificity
D000470:Alkaloids; D018076:DNA, Complementary; D009019:Morphinans; D010940:Plant Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D009020:Morphine; C009270:salutaridine; D010088:Oxidoreductases