B₁₂/Folate Problem set

Question 3: Effect of folate-B₁₂ disruptions on neural membranes

Which important enzyme cofactor, crucial to the integrity of neural membranes, is produced from methionine?

A.	homocysteine
B.	NADPH
C.	tetrahydrobiopterin
D.	S-adenosylmethionine Perhaps a giveaway, since methionine is part of the answer! At any rate, S-adenosyl methionine (SAM, for short) is the critical link between the folate-B12 pathways and the neural symptoms produced when either pathway is disrupted. SAM is a crucial methyl donor for, among other things, the synthesis of phosphatidylcholine and sphingomyelin for neural membranes [Note that the lung, another tissue highly dependent on some of these same lipids, has a recycling pathway that does not require SAM.] Thus, the requirement of B12 for SAM formation is critical, but there is another part to the B12 story...
E.	glutathione