Amino Acid Metabolism - the Methionine (SAM) Cycle

The video tutorial explains the SAM cycle, highlighting the formation of S-adenosylmethionine (SAM) from methionine, its role as a methyl donor, and the conversion to S-adenosyl-homocysteine. It discusses the regeneration of methionine, emphasizing the importance of vitamin B12 and folate. The tutorial also covers the consequences of deficiencies in these vitamins, such as elevated homocysteine levels and potential cardiovascular risks.

What is the primary role of S-adenosylmethionine (SAM) in the body?

• To act as a universal methyl donor

• To transport oxygen

• To store energy

• To break down proteins

Which enzyme catalyzes the formation of S-adenosylmethionine from methionine?

• Pyruvate kinase

• Methionine synthase

• Methionine adenosyl transferase

• S-adenosyl-homocysteine hydrolase

What happens to the methyl group of S-adenosylmethionine during methylation reactions?

• It is oxidized

• It is reduced

• It is hydrolyzed

• It is transferred to a nucleophile

Which cofactors are required for the conversion of homocysteine to methionine?

• Coenzyme Q10 and biotin

• N5-methyltetrahydrofolate and cobalamin

• ATP and GTP

• NADH and FADH2

What is the role of cobalamin in the methionine cycle?

• It hydrolyzes S-adenosylmethionine

• It oxidizes methionine

• It receives and donates a methyl group

• It acts as a methyl donor

What is a potential consequence of cobalamin deficiency in the methionine cycle?

• Increased methionine levels

• Elevated homocysteine levels

• Increased DNA synthesis

• Decreased homocysteine levels

Why is it important to maintain adequate levels of folate and vitamin B12?

• To prevent protein synthesis

• To ensure efficient DNA replication

• To support the methionine cycle and prevent cardiovascular diseases

• To increase energy storage