Abstract
Along the poppy morphine biosynthetic pathway, the transition from salutaridinol-7-O-acetate to thebaine had previously been claimed to proceed non-enzymatically between pH 8–9. At pH 6–7, the acetate was transformed to an azonine derivative. These transformation reactions were revisited using Papaver somniferum protein extracts in search for a possible protein catalyst. After removal of residues and inhibitory low molecular weight compounds from the latex of P. somniferum, this latex serum was shown to convert salutaridinol-7-O-acetate to thebaine in high yield at the physiological pH of 7.0. A new enzyme, which was partly purified, was shown to catalyze this reaction and was partly characterized. As a result, a further enzymatic step had to be added to the morphine pathway in the poppy plant, involved in the transformation of 2 moles L-tyrosine to one mole of morphine.