A glycyl radical solution: oxygen-dependent interconversion of pyruvate formate-lyase

Area of Science:

• Biochemistry
• Enzymology
• Radical Chemistry

Background:

• Pyruvate formate-lyase (PFL) catalyzes pyruvate to formate and acetyl-CoA via a radical mechanism.
• Active PFL contains a glycyl residue radical, formed anaerobically by an iron-sulfur protein activating enzyme.
• PFL is oxygen-inactivated and converted to a stable form by alcohol dehydrogenase during aerobic transition.

Purpose of the Study:

• To investigate the radical chemical mechanism of Pyruvate formate-lyase (PFL).
• To explore the activation and inactivation pathways of PFL in response to oxygen.
• To examine the genetic organization and evolutionary prevalence of PFL and related enzymes.

Main Methods:

• Enzymatic assays to study PFL activity and interconversion.
• Biochemical analysis of the radical formation and oxygen-induced inactivation.
• Comparative genomics to assess the distribution of PFL-encoding genes.

Main Results:

• PFL radical formation requires anaerobic conditions and specific activating enzymes.
• Oxygen rapidly inactivates PFL, necessitating conversion to a stable, radical-free form.
• PFL and its activating enzyme genes are often co-located and conserved across diverse anaerobic organisms.
• PFL-like proteins and glycyl radical enzymes are more widespread than previously thought.

Conclusions:

• Glycyl radical enzymes, like PFL, possess unique biochemistry and likely predate oxygen.
• The regulation of PFL activity is crucial for anaerobic energy metabolism and survival in changing oxygen levels.
• The prevalence of PFL-like enzymes suggests significant roles in diverse microbial metabolisms.