New insights into the first oxidative phenol coupling reaction during vancomycin biosynthesis

Area of Science:

• Biochemistry
• Enzymology
• Natural Product Biosynthesis

Background:

• Vancomycin biosynthesis involves oxidative phenol coupling catalyzed by OxyB.
• OxyB is a P450 hemoprotein requiring molecular oxygen for activity.

Purpose of the Study:

• To investigate the mechanism of OxyB in vancomycin biosynthesis.
• To determine if OxyB incorporates molecular oxygen into the product.
• To assess the stereospecificity of OxyB in substrate binding and catalysis.

Main Methods:

• Isotopic labeling with (18)O(2) to trace oxygen incorporation.
• Enzymatic conversion of a model hexapeptide substrate with an (R)-Tyr6 epimer.
• UV-vis spectroscopy to monitor substrate binding to OxyB.

Main Results:

• (18)O(2) label was not incorporated into the monocyclic product.
• OxyB converted the (R)-Tyr6 epimeric substrate into the corresponding epimeric monocyclic product.
• Binding studies revealed a K(d) of 35+/-5 microM for the epimeric hexapeptide-PCP conjugate.

Conclusions:

• OxyB does not incorporate molecular oxygen into the product of the first oxidative phenol coupling.
• OxyB exhibits a surprising lack of stereospecificity in both substrate binding and catalytic transformation.
• These findings provide new insights into the vancomycin biosynthetic pathway and P450 enzyme mechanisms.