Ascorbic acid is an antioxidant that is also considered an effective dietary supplement that our body can't synthesize; hence, our body's need for Vitamin C is fulfilled through fruits and vegetables, but the amount of vitamin C in them varies. In past decades, extensive information has been gathered about the genes involved in regulating ascorbate biosynthesis. Plethora of studies has unveiled that Smirnoff-Wheeler pathway plays an extensive role in ascorbic acid synthesis. The major challenge among the plant tissues remained the same that is the diversity and variability of L-ascorbic acid among different plant tissues. A diet deficient in vitamin C results in the inception of various diseases, which may show disastrous consequences. However, many studies have shown its implications in preventing multiple diseases, for instance, stroke, heart diseases, cancer, and various other neurodegenerative diseases. The most vital enzyme, L-Galactono-1,4-Lactone Dehydrogenase performs an essential function in the last step attributed to the ascorbic acid pathwayis discussed in this review. GLDH is a miniature form of complex I and is also known as complex I*. Many advancements have been made to regulate ascorbic acid production by overexpressing this enzyme. This review also focuses on cloning strategies and biological functions, structure, and active site of the respective enzyme.Other than this, cloning strategies and biological application have also been discussed.

Ascorbic acid, Antioxidant, Photoprotection, Reactive oxidant species

The review gives a brief about the enzyme L-Galactono-1,4-Lactone Dehydrogenase. GLDH is present in the inner mitochondrial membrane responsible for the final step of ascorbate biosynthesis, where it is produced through L-galactono-1,4-lactone oxidation in association with cytochrome c reduction. This paper also gives an overview of the active sites of this enzyme. Many steps associate in the formation of Vit C, but the final pace where ascorbic acid is produced is by L-Galactono-1,4-lactone's oxidation. L-Galactono-1,4-Lactone Dehydrogenase is the key enzyme that catalyzes this step. Also, a protein family favoured by Flavin Adenine Dinucleotide (FAD), a linked enzyme of VAO i.e. Vanily-1-Alcohol Oxidase, utilizes type-c cytochrome as an acceptor of an electron. These enzymes have a hand in the ascorbic acid synthesis, and also, this enzyme, i.e. GLDH is connected to respiratory complex I in mitochondria. The report also mentions the cloning strategies to increase the accumulation of ascorbate, which adds to resistance to oxidative stress. Ascorbate's significance in various crucial and critical cellular processes is being investigated; the chemical is intriguing for new research. From cell division and growth to offering plant tolerance to environmental stress, ascorbate is engaged in various cellular functions. Current, Vit C research is mainly focused on increasing ascorbate accumulation or overexpression in ascorbate plants to meet the need for vitamin c content. Advanced genomic technologies will significantly impact the research of ascorbate regulation, assembly, and recycling in the future. The application of genetic engineering will enable us to combine two or more biosynthetic gene in expression model organism to regulate the biosynthesis of ascorbic acid and further exploration might be done to understand the effect of different metabolic products in synthesis process. Moreover, the impact of genes clone could also be studied in different model organism and their organs.

Neera, Daljeet Singh Dhanjal, Reena Singh and Chirag Chopra (2022). Biochemical, Pharmaceutical and Biotechnological Perspectives of the Ascorbate Synthesis Gene L-Galactono-1,4-Lactone Dehydrogenase. Biological Forum – An International Journal, 14(2): 469-480.