Methionine/cysteine Metabolism Flashcards
Why is SAM (S-adenosyl methionine important?)
for 1-carbon transfer. It will methylate a histone
where does SAM come from?
Methionine
homocysteine reacts with
serine
when homocysteine and serine reacts they form _____ usine
cystathionine / cystathionine synthase
what cofactor does cystathionine synthase use?
B6/PLP/pyridoxine
how does cystathionine enter the TCA cycle?
It undergoes a transulfation, and then breaks down into propionyl coA–> malonyl coA –> succinyl coA
deficiency in cystathionine synthase causes
homocysteneuria
when you hear cardiovascular disease think
homocysteneuria
can have homocysteneuria 2 ways
1) cystathionine synthase defect or the lack of B12 so you have no remethylation pathway of homoscsteine to methionine
betaine
methyl group donor and can stimulate the formation of methionine from homocysteine
cofactor of BCAAD
thiamine
disease when you have a defect in BCAAD
Maple syrup urine disease
lysine and leucine
are solely ketogenic –> cannot be glucogenic
how is proprionyl coA converted to methyl malonyl coA
propionyl coA carboxylase
what is the cofactor used with proprionyl coA carboxylase
biotin
how do you treat MSUD
thiamine
which enzymes in the branch chain pathway can form glucogenic intermediates
valine and isoleucine
increaed proprionic acid in proprionic aciduria inhibits
NAG synthase, so you dont get N-acetyl glamate, whcih activates CPS1. It also inhibits Glycine cleavage complex
multiple carboxylase deficiency
reduced biotin will effect every carboxylase
what two things will increase in proprionic acidemia
glycine and NH3
how do you treat proprionic acemida?
you will decresae VOMIT and give biotine. You can also use carnitine to saok up an acetly coA, or you can treat with antibiotivs
what do you use carnitine for
carnitine reacts with acetyl coA, and will soak up proprionyl coA and help w proprionyl acidemia
carboxylases use
biotin
dehydrogenases use
thiamine
