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Again, like all my review sheets this is not intended to be a list of all the things that you need to know but is just the review sheet of all the things I feel I still need to study. Only use it to find things that you may have forgotten to memorize.
Tetrahydrofolate is a transporter of methyl groups. Methylene tetrahydrofolate is the one carbon donor.
Glutamine dehydrogenase converts glutamine to a-ketoglutarate
Urease converts urea to carbonic acid.
Carbamoyl phosphate synthetase (in the mitochondria) convert NH4+ + CO2 + 2ATP into carbamoyl phosphate.
Ornithine transcarbmoylase is the first step in the urea cycle converting ornithine and carbamoyl phosphate into citrulline.
Arginase breaks arginine to give urea and ornithine.
AST can be coupled with other transaminases to move the N of other AAs to aspartate to enter the urea cycle.
Benzoate and phenylacetate are complexed with other AAs to allow direct N excretion.
N-acetylglutamate is the regulator of the RDS of the urea cycle. Arginine activates the conversion of acetyl-CoA and glutamate into N-acetylglutamate (NAG). The urea cycle only operates in the presence of NAG.
Propionyl-CoA is an intermediate in the metabolism of many AA metabolic mechanisms. If it or biotin are low you get excess propionate and free FAs.
Methylmalonic acidemia is similar to propionyl-CoA deficiency (free FAs) except it is associated with metabolic acidosis.
Cystathionurea/Honocystinurea involves blockages in the breakdown of methionine and the formation of cystine. You must give cystine supplements and a low methionine diet.
Maple syrup urine disease involves a shortage of branched chain dehydrogenase and causes failure of the breakdown of leucine, isoleucine and valine.
PKU is from shortage of phenylalanine hydroxylase. If it’s not detected early enough it can cause serious neurological problems during development.
Tyrosinemia is a failure of the breakdown of tyrosine and substrates are converted into melanin causing excessive pigmentation. Treat with a diet low in both phenylalanine and tyrosine.
Alcaptonuria blocks the breakdown of both phenylalanine and tyrosine and causes black stuff to end up in the urine.
Hartnup’s Disease is a deficiency of the transporter of AA’s across the renal tubule and intestine. It leads to a low N balance.
Cystinuria is a failure to properly transport AAs across the renal tubules also resulting in a low N balance.
Glucamine is synthesized in the CNS to couple and shuttle N out. It is taken to the kidney’s where it is metabolized and the N excreted in one of it’s forms.
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