Figure 4.

A, Amino acid residues conferring cofactor preference and participating in the catalytic cycle. The colors for the C-skeleton of each structure are: green, salutaridine; light blue, NADPH; and gray, amino acids. Hydrogen, nitrogen, oxygen, and phosphorus atoms are shown in white, blue, red, and orange, respectively. Only interacting hydrogen atoms are shown. Interactions are indicated by a dotted line. B, Schematic drawing of the catalytic cycle. Interactions are indicated by a dotted line and the proton transfer system by arrows.