Codeinone reductase (NADPH)

Codeinone reductase (NADPH) is an enzyme classified under EC number 1.1.1.237. It catalyzes the following chemical reaction:

codeine + NADP⁺ ⇌ codeinone + NADPH + H⁺

This enzyme plays a crucial role in the biosynthesis of morphine alkaloids in plants, particularly the opium poppy ( Papaver somniferum ). Specifically, it catalyzes the NADPH-dependent reduction of codeinone to codeine. Codeine is a direct precursor to morphine in the morphine biosynthetic pathway.

The enzyme is a monomeric protein that utilizes NADPH as a cofactor. It exhibits high substrate specificity for codeinone and shows little or no activity with other related compounds. The reductase activity is essential for the efficient production of morphine and other therapeutically important alkaloids.

The gene encoding codeinone reductase has been identified and characterized in opium poppy. Studies on the enzyme have contributed to the understanding of the morphine biosynthetic pathway and have provided insights into potential strategies for metabolic engineering to enhance the production of morphine alkaloids or to create novel alkaloids. Furthermore, research has focused on the structural properties of the enzyme to better understand its catalytic mechanism and substrate binding.