L-gulono-γ-lactone Oxidase, the Key Enzyme for L-Ascorbic Acid Biosynthesis
- Author: mycolabadmin
- 10/1/2024
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Summary
Vitamin C (ascorbic acid) is essential for human health, protecting against disease and supporting numerous body functions. However, humans cannot make their own vitamin C because we lack a functional GULO enzyme gene. This review examines how different organisms produce vitamin C, where these enzymes work in cells, and recent discoveries showing that a simplified version of the enzyme can still work effectively, which could help improve vitamin C production in engineered plants.
Background
L-ascorbic acid (vitamin C) plays a vital role in preventing various diseases and possesses antioxidant properties. The final step in ascorbic acid biosynthesis is catalyzed by L-gulono-γ-lactone oxidase (GULO), which is absent in humans, guinea pigs, bats, and other primates, making them unable to synthesize ascorbic acid.
Objective
This review explores ascorbic acid production, biosynthetic pathways in both animals and plants, localization of GULO-like enzymes, and comparison of amino acid sequences across species. The study focuses on understanding GULO enzymatic activity and the significance of the HWXK motif for enzyme function.
Results
The review demonstrates that recombinant C-terminal rat GULO expressed in E. coli shows enzymatic activity despite lacking the N-terminal FAD-binding domain, suggesting the C-terminal HWXK motif is sufficient for flavin cofactor binding. Seven GULO-like enzymes (GULLO1-7) were identified in Arabidopsis thaliana with varying domain structures and localizations.
Conclusion
The HWXK motif at the C-terminus is essential for forming the active site and binding the flavin cofactor in GULO enzymes. This finding has implications for understanding GULLO7 from Arabidopsis, which lacks the FAD-binding domain but may retain enzymatic activity through its C-terminal motif.
- Published in:Current Issues in Molecular Biology,
- Study Type:Review,
- Source: PMID: 39451537