Amino acid disorders Flashcards
Cystine vs cysteine
Cystine – aa formed from 2 cysteines w/ disulfide bond
Albinism
Congenital
Normal number of melanocytes, decreased melanin
Defective tyrosine transport or deficient tyrosinase
Increased skin cancer
Homocystinuria
Deficient in cystathionine synthase or decreased affinity of enzyme for B6 cofactor (pyridoxal phosphate)
-can’t convert homocysteine to cystathione -> cysteine
Tx: decrease methionine in diet
Deficient homocysteine methyl transferase
-cant convert homocysteine to methionine
elevated homocysteinuria
Sx: Intellectual disability Tall stature Osteoporosis Kyphosis Atherosclerosis Subluxation of lens – downward!
Tx: increase cysteine, increase B12, B6 to bypass pathway
Alkaptonuria
Causes ochronosis
AR – deficient homogentisate oxidase
-can’t degrade tyrosine
Homogentisic acid builds up in urine and connective tissue – brown
Sclera brown spots
Urine turns back as exposed to air
Arthralgias
Tx: add Vit C
Restrict phenylalanine and tyrosine
Not very effective
S-adenosyl methionine (SAM)
Transfers methyl units
Important for NE -> Epi
Synthesis for phosphocreatinine
Made ATP + methionine
Need B12 and folate to regenerate methionine
Cystinuria
Defect of renal tubular aa transporter for COLA
- Cystine
- Ornithine
- Lysine
- Arginine
found in PCT normally
- > cystine kidney stones
- prevent w/ acetazolamide
Maple syrup urine dz
“I LoVe Maple syrup”
Isoleucine, leucine, valine
-branched aa
deficiency of branched chain alpha-ketoacid dehydrogenase complex
Intellectual diability
Severe CNS defects
Hartnip Disease
AR
Defect of transporter in intestine and kidneys
Transport neutral aa
Trp -> excreted in urine not absorbed
-can’t make Niacin w/o Trp -> Pellagra (B3 def)
3 Ds of B3 (Niacin) Deficiency:
Dermatitis
Diarrhea
Dementia
