Nitrogen Metabolism Flashcards
What substrates are affected by hartnup disease
Neutral amino acids
[defective transporter]
Common treatment for hartnup
Supplement with niacin or nicotinic acid (B3) to increase production of NAD or NADP (bc Trp is a precursor to those)
Individual substrates affected in Cystinuria
COAL - dibasic amino acids
Cystine, ornithine, arginine, lysine
Major clinical manifestation of cystinuria
Cystine nephrolithiasis
Of the individual substrates affected in Cystinuria, ______ is a non-protein amino acid which is a substrate in the urea cycle
Ornithine
Why are cystinuria and hartnup considered double-whammy diseases
Malabsorption in intestinal lumen AND decreased reabsorption from filtrate (bc defective transporters in intestine and kidney!)
Rate limiting step of urea cycle
Conversion of ammonia to carbamoyl phosphate by CPSase I and NAG activation
What is the carbon skeleton for urea cycle transamination reactions?
Aspartate
What is the first step of nitrogen removal from the body?
Oxidative deamination by glutamate dehydrogenase
What enzyme is affected in PKU
Phenylalanine hydroxylase
Difference between classic and non-classic PKU
Classic = deficiency in PAH
Non-classic = THB deficiency, a necessary cofactor for PAH
[note that THB is also necessary for NO production from Arg, it is regenerated from NADPH-dependent reduction of BH2]
What IEM results in musty urine odor and is the most common IEM?
PKU
PKU is treated dietarily and with supplementation of ____. metabolic control improves with treatment with _____
Tyr
THB
Which type of tyrosinemia is most common, what are the symptoms
Type 1 - cabbage smelling urine, severe liver failure (need transplant), inhibition of heme biosynthesis
What type of tyrosinemia is a defective tyrosine aminotransferase and presents as photophobia and skin lesions on palms+soles?
Type II
