Nitrogen Flashcards
What is Hartnup Disease?
Defect in the transporter responsible for reabsorption of Neutral/Non-Polar amino acids (Ala, Ser, Thr, Val, Leu, Ile, Phe, Tyr, Trp, Gln, Asn, His) in the proximal tubule.
Causes excretion of these amino acids
Trp is precursor for niacin, which is needed for NAD production
Photosensitivity is present
Treatment involves high protein diet and niacin repletion
What is Cystinuria?
Defect in transporter responsible for reabsorption of COAL (Cystine, Ornithine, Arginine, Lysine) - the dibasic amino acids.
Results in formation of cystine crystals in kidney
What is Phenylketouria?
Defects in the activity of PAH (phenylalanine hydroxylase)
PAH is responsible for the conversion of Phenylalanine to Tyrosine.
Defective PAH causes accumulation of Phenylalanine, which is converted to Phenyllactate (causing musty odor in urine)
Also causes impairment of brain function
Treatment is dietary limit in phenylalanine and tyrosine supplementation
What is Tyrosinemia type I?
Most common type
Elevated levels of Tyrosine due to defect in fumarylacetoacetate hydrolase enzyme (which normally converts tyorsine into fumarate)
Causes infants to have cabbage like smell and severe liver damage if not treated.
What is Alkaptonuuria?
“Black Urine disease”
Due to defective homogentisate oxidase enzyme (involved in tyrosine degradation pathway)
Autosomal Recessive disease
Causes black pigment in urine, arthritis, and ochronosis (accumulation of black pigment in skin and eyes)
Black pigment is oxidized Homogentisic acid
What is Gout?
High levels of uric acid (urate) in the blood
Primary uricemia = overproduction of uric acid
Secondary uricemia = underexcretion of uric acid
Painful depsoits of sodium urate crystals in joints
What is Ammonia toxicity?
Excessive ammonia due to disorders in the urea cycle or liver failure
Causes highly toxic effects on CNS and brain
What is hyperammonemia?
Excess ammonia in the blood
Occurs with defects in any of the 6 enzymes associated with the urea cycle or the 3 transporters
Defect in the ornithine transcarbamoylase is the only X-linked form of hyperammonemia
What is Carbamoyl Phosphate Synthetase II?
CPSII is a cytosolic enzyme unique from the mitochondrial isoform in the urea cycle (CPSI)
Involved in pyrimidine synthesis
PRPP-activated
How does jaundice occur in newborns?
Elevated bilirubin (jaundice) is normal after birth
Placenta normally removes removes bilirubin, so it take a little time for liver to start doing its job
Severe jaundice can occur if there is an increased need to replace the number of red blood cells (such as sickle cell)
Blue-florescent light allows photochemical conversion of bilirubin to water soluble isomers
What is the difference between direct and indirect bilirubin?
Direct Bilirubin (reddish/pink-purple product) results from soluble (conjugated bilirubin) reacting with Diazo reagent.
Indirect Bilirubin is the result of insoluble (unconjugated) bilirubin made soluble by 50% methanol, which is then able to react with Diazo reagent.
What is the rate limiting step in nitrogen metabolism?
The conversion of ammonium (NH4+) into Carbamoyl Phosphate, with the help of the Carbamoyl Phosphate Synthetase I enzyme.
CPSI functions in the urea cycle, is found in the liver mitochondria, and is NAG-activated
What is tyrosinemia type II?
Defective tyrosine amino transferase ezyme
Causes photophobia and skin lesions in palms and soles
What is tyrosinemia type III?
Defective p-hydroxyphenylpyruvate oxidase enzyme
Results in intermittent ataxia (loss of control of body movements)
