A 32-year-old primigravid woman at 23 weeks’ gestation presents to her obstetrician for a prenatal appointment. She has not received any prenatal care up to this point and does not take any vitamin supplements. On physical examination, she is noted to be pale. Neurological examination shows no abnormalities. A peripheral blood smear shows a megaloblastic anemia that is suspected to be linked to a vitamin deficiency.
Which of the following biochemical process is most directly impacted by the suspected deficiency?
A) Glycolysis
B) Pyrimidine synthesis
C) Transcription
D) Translation
E) Ubiqutination
B) Pyrimidine synthesis
Folate (vitamin B9) is vital in the synthesis of thymine, a DNA base. Once it is "trapped" by vitamin B12 (i.e., it becomes tetrahydrofolate [TH4]), it enters a series of reactions that eventually lead to the generation of dTMP (deoxythymidylate monophosphate). TH4 first reacts with serine to produce glycine and 5, 10 methylenetetrahydrofolate (N5N10-methylene FH4). The latter goes on to react with deoxyuridylate monophosphate (dUMP) to form dTMP with the help of the enzyme thymidylate synthase. As this process is a crucial source of thymine for DNA synthesis, its disruption will severely hinder DNA replication.
Key Learning Point
The nucleotide base, thymidine, requires folate for its generation. Without folate, DNA replication can be severely hindered.
