One Carbon Metabolism Flashcards
Carbon source for SAM?
Methionine
Carbon source for Biotin
CO2
How many methylation reactions does FH4 participate in
Only one methylation reaction, all others use SAM
Biotin is the cofactor for what 3 major carboxylases
Pyruvate carboxylase, Acetyl CoA carboxylase, and Propionyl Carboxylase
What is the first enzyme in fatty acid synthesis
Acetyl CoA carboxylase
Pyruvate carboxylase is the first enzyme in what metabolic pathway?
Gluconeogenesis
One way to get biotin deficiency…
eat 20 raw egg whites in one day
In biotin carboxylase, where is biotin attached
to the Epsilon amino group of lysine
Biotinidase is present in cells and serum, and it cleaves biotin from
proteins
Holocarboxylase synthetase deficiency can result in
encephalopathic crisis (brain damage) and hair loss
SAM is synthesized in a reaction involving both
Methionine and ATP
SAM is a major carrier of ________ groups in metabolism
methyl
Two possible fates of homocysteine
Homocysteine is converted to methionine or used in cysteine synthesis
S-Adenosyl homocysteine is hydrolyzed to
adenosine and homocysteine
What is the MAJOR carrier of C1 groups in metabolism?
Tetrahydrofolate (FH4)
FH4 is a reduced form of
folic acid
What can synthesize folate
Not humans. Bacteria and higher plants synthesize folate
Why do pregnant women supplement with folic acid?
To prevent neural tube defects
Folate is converted to FH4 by 2 reactions with what one enzyme?
dihydrofolate reductase in an NADPH dependent reaction
What body organ stores about half of the body’s FH4?
liver
What form is folate absorbed in by the small intestines?
Monoglutamate
What two positions do C1 units bind to on FH4?
N5 and/or N10
Formyl groups bind _____, methyl groups bind ____, while Methenyl and methylene groups form carbon bridges between
N10
N5
N5 and N10
Most C1 acceptors are intermediates in
purine and pyrimidine synthesis
