Investigation of Helicobacter pylori ascorbic acid oxidating activity

Area of Science:

• Microbiology
• Biochemistry

Background:

• Helicobacter pylori is a significant human pathogen.
• Ascorbic acid (Vitamin C) is crucial for health and is present in gastric juice.

Purpose of the Study:

• To investigate the mechanism of ascorbic acid oxidation by Helicobacter pylori.
• To characterize the enzyme responsible for this oxidation.

Main Methods:

• Chromatography with electrochemical detection was used to measure ascorbic acid oxidation.
• Gel filtration and detergent extraction were employed to isolate and characterize the oxidizing activity.
• pH optima and molecular weights of the oxidants were determined.

Main Results:

• Helicobacter pylori sonicate demonstrated ascorbic acid oxidase activity.
• A water-soluble, cytochrome c-like molecule (Mr ~14,000) with a pH optimum of 2 was identified.
• A membrane-associated form (Mr ~19,000) with a pH optimum of 6-7 was also found.
• Other bacterial strains, including Campylobacter coli, Enterobacter cloacae, and Pseudomonas aeruginosa, also degraded ascorbic acid.

Conclusions:

• Helicobacter pylori possesses both soluble and membrane-bound enzymes that oxidize ascorbic acid.
• The acidic pH optimum of the soluble enzyme aligns with the gastric environment, suggesting its role in ascorbic acid destruction in infected patients.
• This enzymatic activity may contribute to the pathogenesis of H. pylori by depleting a key antioxidant in the stomach.