title: Evolution of morphine biosynthesis in opium poppy.
abstract: Benzylisoquinoline alkaloids (BIAs) are a group of nitrogen-containing plant secondary metabolites comprised of an estimated 2500 identified structures. In BIA metabolism, (S)-reticuline is a key branch-point intermediate that can be directed into several alkaloid subtypes with different structural skeleton configurations. The morphinan alkaloids are one subclass of BIAs produced in only a few plant species, most notably and abundantly in the opium poppy (Papaver somniferum). Comparative transcriptome analysis of opium poppy and several other Papaver species that do not accumulate morphinan alkaloids showed that known genes encoding BIA biosynthetic enzymes are expressed at higher levels in P. somniferum. Three unknown cDNAs that are co-ordinately expressed with several BIA biosynthetic genes were identified as enzymes in the pathway. One of these enzymes, salutaridine reductase (SalR), which is specific for the production of morphinan alkaloids, was isolated and heterologously overexpressed in its active form not only from P. somniferum, but also from Papaver species that do not produce morphinan alkaloids. SalR is a member of a class of short chain dehydrogenase/reductases (SDRs) that are active as monomers and possess an extended amino acid sequence compared with classical SDRs. Homology modelling and substrate docking revealed the substrate binding site for SalR. The amino acids residues conferring salutaridine binding were compared to several members of the SDR family from different plant species, which non-specifically reduce (-)-menthone to (+)-neomenthol. Previously, it was shown that some of these proteins are involved in plant defence. The recruitment of specific monomeric SDRs from monomeric SDRs involved in plant defence is discussed.
authors: Leibniz-Institute of Plant Biochemistry, Halle, Germany.
authors: Jörg
authors: J
authors: Ziegler
authors: Peter J
authors: PJ
authors: Facchini
authors: René
authors: R
authors: Geissler
authors: Jürgen
authors: J
authors: Schmidt
authors: Christian
authors: C
authors: Ammer
authors: Robert
authors: R
authors: Kramell
authors: Susan
authors: S
authors: Voigtländer
authors: Andreas
authors: A
authors: Gesell
authors: Silke
authors: S
authors: Pienkny
authors: Wolfgang
authors: W
authors: Brandt
mesh_terms: D000470:Alkaloids / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D044182:Benzylisoquinolines / Q000737:chemistry / Q000302:isolation & purification*; D003674:Defense Mechanisms; D019143:Evolution, Molecular; D015394:Molecular Structure; D009020:Morphine / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D010207:Papaver / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D000470:Alkaloids; D044182:Benzylisoquinolines; D009020:Morphine; C003298:reticuline