Biochem 4 Flashcards
Phenylketonuria path
Decreased Phe hydroxylase or dec. tetrahydrobiopterin cofactor (malignant PKU)
What is malignant PKU?
Neonatal PKU due to tetrahydrobiopterin (BH4) deficiency
Phenylketonuria labs
excess phenylketones in urine
PKU presentation
MR, growth retardation, seizures, fair skin, eczema, musty body odor.
PKU tx
decrease Phe and increase tyrosine in diet
what amino acid is essential in PKU
tyrosine before essential
PKU genetics
aut. rec. (1/10,000)
When does PKU appear
2-3 days after birth (enzyme from mother)
What are the phenylketones
phenylacetate, phenyllactate, and phenylpyruvate
Maternal PKU path and presetnation
lack of proper diet therapy during pregnancy. Infant has microcephaly, intellectula disability, growth retardation, congenital heart defects.
Alkaptonuria alternate name
Ochronosis
Homocystinuria types and genetics
3 types. All aut. rec.
- Cystathionine synthase deficiency
- Decreased affinity of cystathionine synthase for pyridoxal phosphate
- Homocysteine methyltransferase (methionine synthase) deficiency
Homocystinuria presentation
All forms result in excess homocysteine. MR, osteoporosis, tall stature, kyphosis, lens subluxation downward and inward, thrombosis, and atherosclerosis (stroke and MI)
Homocystinuria labs
elevated homocysteine in urine
Cystathionine synthase deficiency tx
lower methionine, increase cysteine, increase b12 and folate in diet
decreased affinity of cystathionine synthase for pyridoxal phosphate tx
increased b6 and cysteine in diet
homocysteine methyltransferase deficiency tx
increase methionine in diet
why does adding cysteine and methionine help with homocystinuria………
Not because it reverses any issues with homocysteine, it just helps in supplying methionine and cysteine which are needed in our bodies!
Cystinuria genetics and path
Aut. rec. (Common 1:7,000) hereditary defect of renal PCT and intestinal amino acid transporter for Cysteine, ornithine, Lysine, and Arginine (COLA)
Cystinuria presentation
Excess cystine in urine can lead to precipitation of hexagonal cystine stones
Cystinuria labs
urinary cyanide-nitroprusside test is diagnostic
Cystinuria tx
urinary alkalinization (e.g. potassium citrate, acetazolamide) and chelating agents increase solubility of cystine stones; good hydration
What is a cystine bond
2 cysteines connected with a disulfide bond
Maple syrup urine disease genetics and path
Aut. rec. Blocked degradation of branched amino acids (isoleucine, leucine, valine) due to decreased alpha-ketoacid dehydrogenase (B1). Causes increased alpha-ketoacids in blood especially leucine.