Folic Acid Metabolism | Folate Cycle

Summary

This video explains folic acid metabolism, also known as folate metabolism, highlighting its importance as vitamin B9. It details the absorption of folate in the duodenum and jejunum, emphasizing two key enzymes: polyglutamate hydrolase and dihydrofolate reductase. The video discusses the dietary forms of folate, including polyglutamate and monoglutamate, and outlines the conversion processes leading to the synthesis of tetrahydrofolate. The role of tetrahydrofolate in DNA and purine synthesis is also explored, illustrating the vital functions of folate metabolism in cellular processes.

Takeaways

• 😀 Folic acid, also known as vitamin B9 or folacin, is crucial for various bodily functions.
• 🧬 Folic acid metabolism involves absorption primarily in the duodenum and jejunum, the initial parts of the small intestine.
• 🔬 The two key enzymes in folate metabolism are: 1) Polyglutamate hydrolase (folate conjugase), found in the jejunal mucosa, and 2) Dihydrofolate reductase (DHFR), located in the liver.
• 🍽️ Dietary folic acid exists in two forms: polyglutamate folate (which needs conversion) and monoglutamate folate (which is directly absorbed).
• ⚙️ Monoglutamate folate is directly absorbed into the liver, while polyglutamate folate must first convert to monoglutamate in the jejunum.
• 📉 Dihydrofolate reductase reduces monoglutamate folate to dihydrofolate using NADPH as an electron donor.
• 🔄 Dihydrofolate is further reduced to tetrahydrofolate (THF) by DHFR, also utilizing NADPH.
• 🌱 Tetrahydrofolate can accept a one-carbon unit from serine to form 5,10-methylene tetrahydrofolate, catalyzed by serine hydroxymethyltransferase (SHMT).
• 💡 5-methyl tetrahydrofolate combines with homocysteine in the presence of methylene synthase to regenerate THF and participate in the methionine cycle.
• 🧬 Folic acid metabolism plays a critical role in DNA synthesis and purine synthesis, highlighting its importance in cellular function.

Q & A

What is folic acid also known as?

Folic acid is also known as folate, vitamin B9, or folacin.

Where in the body is folic acid absorbed?

Folic acid is primarily absorbed in the duodenum and jejunum, which are parts of the small intestine.

What are the two dietary forms of folic acid?

The two dietary forms of folic acid are polyglutamate folate and monoglutamate folate.

How is monoglutamate folate absorbed?

Monoglutamate folate is absorbed directly by the small intestine and then transported to the liver.

What happens to polyglutamate folate before absorption?

Polyglutamate folate is first converted into monoglutamate folate in the jejunum before it can be absorbed.

What are the key enzymes involved in folic acid metabolism?

The key enzymes involved are polyglutamate hydrolase (folate conjugase) and dihydrofolate reductase (DHFR).

What role does dihydrofolate reductase play in folic acid metabolism?

Dihydrofolate reductase reduces monoglutamate folate to dihydrofolate and then to tetrahydrofolate, using NADPH as an electron donor.

How does tetrahydrofolate participate in one-carbon metabolism?

Tetrahydrofolate is converted into 5,10-methylene THF, which accepts a one-carbon unit from serine, leading to the production of glycine.

What is the significance of 5-methyl THF in folate metabolism?

5-methyl THF combines with homocysteine to regenerate tetrahydrofolate and produce methionine, playing a crucial role in methylation reactions.

How does folic acid metabolism contribute to DNA synthesis?

Folic acid metabolism leads to the formation of deoxythymidine monophosphate (dTMP) from deoxyuridine monophosphate (dUMP), which is essential for DNA synthesis.