7. Nitrogen Metabolism Flashcards
What is the main nitrogen shuffling molecule for the liver?
Glutamate
What is the main nitrogen shuffling molecule for the rest of the body (other than the liver)?
Glutamine
What enzyme catalyzes the rate limiting step of the urea cycle?
Carbamoyl phosphate synthetase 1
What sort of amino acids have a defective reabsorption in Hartnup disease?
Nonpolar amino acids
What sort of amino acids fail to reabsorb in cystinuria?
Dibasic amino acids
Tryptophan is a precursor for what 3 important molecules?
Serotonin, Melatonin, and Niacin
Four of the diseases we studied in this lecture are associated with the phenylalanine to fumarate pathway. What are those diseases, and in what order do they appear in the pathway?
Phenylketonuria
Tyrosinemia II & Albinism
Tyrosinemia III
Alkaptonuria
Tyrosinemia I
What is the cause of secondary phenylketonuria?
Defects in the biosynthesis or regeneration of tetrahydrobiopterin
What enzyme is defective in alkaptonuria?
Homogentisate oxidase
What are the two effects of ammonia toxicity discussed in class?
Ammonia buildup pushes the glutamate to alpha ketoglutarate reaction away from alpha ketoglutarate, which prevents it from going into the TCA cycle.
Also, excess ammonia favors glutamine formation from glutamate, which reduces the amount of glutamate overall, decreasing the amount available to make GABA.
The majority of urea cycle enzyme diseases have what sort of heredity?
Autosomal recessive
(The noted exception is ornithine transcarbamoylase)
What is the function, location, and activator for CPSase II?
Pyrimidine synthesis
Cytosolic
PRPP
What is the function, location, and activator for CPSase I?
Urea cycle
Mitochondrial
NAG
What is the function of UDP glucuronyl transferase?
It conjugates bilirubin
In a newborn, what sort of condition (generally speaking) could cause physiological jaundice to transfer to pathological jaundice?
Anything that causes heme turnover. Blood loss, bruising, anemia, (including sickle-cell), or even infection, because antibiotics decrease/diminish UDP glucuronyl transferase
