Characterization of 1,2-Propanediol Dehydratases Reveals Distinct Mechanisms for B12-Dependent and Glycyl Radical Enzymes.

Abstract

Propanediol dehydratase (PD), a recently characterized member of the glycyl radical enzyme (GRE) family, uses protein-based radicals to catalyze the chemically challenging dehydration of ( S)-1,2-propanediol. This transformation is also performed by the well-studied enzyme B12-dependent propanediol dehydratase (B12-PD) using an adenosylcobalamin cofactor. Despite the prominence of PD in anaerobic microorganisms, it remains unclear if the mechanism of this enzyme is similar to that of B12-PD. Here we report 18O labeling experiments that suggest PD and B12-PD employ distinct mechanisms. Unlike B12-PD, PD appears to catalyze the direct elimination of a hydroxyl group from an initially formed substrate-based radical, avoiding the generation of a 1,1- gem diol intermediate. Our studies provide further insights into how GREs perform elimination chemistry and highlight how nature has evolved diverse strategies for catalyzing challenging reactions.

• Authors: Benjamin J Levin, Emily P Balskus
• Journal: Biochemistry (Biochemistry) Vol. 57 Issue 23 Pg. 3222-3226 (06 12 2018) ISSN: 1520-4995 [Electronic] United States
• PMID: 29526088 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Bacterial Proteins
• Cobamides
• Free Radicals
• Hydro-Lyases
• Glycine

Topics

• Anaerobiosis
• Bacterial Proteins (chemistry, genetics, metabolism)
• Clostridiales (enzymology, genetics)
• Cobamides (chemistry, genetics, immunology)
• Free Radicals (chemistry, metabolism)
• Glycine (chemistry, metabolism)
• Hydro-Lyases (chemistry, genetics, metabolism)