The Role of Serine - 246 in Cytochrome of 6 - Deoxyerythronolide B JStsA P 450 eryF - Catalyzed Hydroxylation

of cytochrome P450 enzymes participates in a proton deliyery system for binding and cleavage of dioxygen molecules. 6-Deoxyerythronolide B hydroxylase (P450eryF) is unusual in that the conserved threonine residue is replaced by a]anine in this enzyme. On the basis of the crystal structures of substrate-bound P450eryF, it has been proposed that the C-5 hydroxyl group of the substrate and serine-246 of the enzyme form hydrogen bonds with water molecules 519 and 564, respectiyely. This hydrogeH bonding network constitutes the proton deliyery system whereby P450eryF maintains its catalytic actiyity ill the absence of a threonine hydroxyl group in the conseryed position. To f"r-