Sulfur Metabolism Flashcards
In general, what is SAM used for?
methyl donor in synthesis reactions
what is SAM used to synthesize? (6)
epinephrine creatine methylated nucleotides phos-choline melatonin sarcosine
2 reactions in creatine synthesis
arginine + glycine –> guanidinoacetic acid with AGAT
guanidinoacetic acid + SAM –> creatine with GAMT
what is the use of creatine in muscle?
creatine serves as an immediate energy source in muscle (creatine-P donates P to form ATP)
what is the difference between creatine and creatinine?
creatinine is the degradation product of creatine
what happens with GAMT deficiency?
decreased GAMT = decreased creatine
causes d/o of CNS- autism, self-mutilation, seizures
why does beatine supplementation help to lower homocysteine levels?
gives an alternative pathway for homocysteine –> methionine, avoiding the use of folate and B12
what are the precursors for cysteine synthesis?
methionine (via homocysteine) donates SH
serine donates carbon skeleton
what are the steps in cysteine synthesis? cofactor?
1- homocysteine + serine –> cystathionine by cystathione B-synthase
2- cystathione –> cysteine by cystathionase
PLP is cofactor for both steps
what is taurine?
taurine is an amino sulfuric acid that is made from cysteine
uses of taurine
used to form conjugated bile salts
abdundant in retina and WBCs, used for brain and retinal development
why is taurine essential for neonates?
they have limited ability to synthesize it from cysteine, so it is required in the diet. it is needed for bile salt conjugation, retinal and neural development
which defects of cysteine synthesis leads to hyperhomocysteinemia?
cystathione B-synthase deficiency
what are the consequences of hyperhomocystenemia?
increased risk of heart attack, CVA, thromboembolism
what is a therapeutic to treating hyperhomocysteinemia caused by cystathione B-synthase def?
high doses of PLP
