Flashcards in Biochem metabolism Deck (129)
How does benzoate or phenyl butyrate treat hyperammonemia?
both bind amino acid & lead to excretion
How does lactulose treat hyperammonemia?
it is a sugar that is not absorbed so gets to colon & bacteria there have a feast thus making the colon acidic causing binding of the NH4+ for excretion
What is the MC urea cycle disorder? How is it inherited? When does it present?
ornithine transcarbamoylase deficiency is XLR presenting in first few days of life but can present later
What are the labs of OTC deficiency?
excess carbamoyl phosphate in mitochondria spills out & is converted to orotic acid (part of pyrimidine synthesis)
increased orotic acid in blood & urine, decreased BUN, Sx of hyperammonemia (tremor, vomit, somnolence, cerebral edema)
Differentiate OTC deficiency vs orotic aciduria
OTC deficiency is NOT associated w/ megaloblastic anemia
What are the derivates of phenylalanine?
(via BH4) tyrosine to make Dopa (vit B6) DA, (vit C) NE, (SAM) Epi
derivates of tryptophan
(vit B6) niacin to NAD+/NADP+
(BH4) serotonin to melatonin
derivates of histidine
(vit B6) histamine
derivates of glycine
(via B6) porphyrin to heme
derivates of arginine
(BH4) nitric oxide
derivates of glutamate
(via B6) GABA;
What amino acid derives melanin? How?
phenylalanine (BH4) to tyrosine to (BH4) Dopa which is converted to melanin
What amino acid derives thyroxine?
Phenylalanine via BH4 to tyrosine to thyroxine
derivates of methionine
What are the respective breakdown products of catecholamines? how are they broken down?
MAO & COMT breaks down
DA to HVA
NE to VMA
Epi to metanephrine
What is the etiology of PKU? What will be found in urine?
AR decrease in phenylalanine hydroxylase (adds OH) or decrease in BH4 (malignant PKU)
phenylketones in urine (phenylacetate, phenyllactate, phenylpyruvate)
When does PKU typically present & earliest signs?
2-3 days after birth bc uses mother's enzyme during fetal life
musty odor due to aromatic AA metabolism
Findings of child with PKU
mental & growth retardation;
Treatment of PKU
decrease Phe in diet (NO aspartame ~ nutrasweet)
Increase tyrosine (essential AA now)
Must be done w/in first 3 wks
Maternal PKU can occur how? what are the findings in the child?
lack of proper diet during pregnancy
microcephaly; growth & mental retardation; congenital heart defects
Pt notices urine turns black in the air & presents to ortho w/ debilitating joint pain. What is the disease caused by?
Alkaptonuria (ochronosis) =>
AR congenital deficiency of homogentisic acid oxidase in degradation of tyrosine to fumarate
What are the findings of alkaptonuria?
dark connective tissue;
brown pigmented sclera;
urine turns black w/ air exposure;
May have debilitating arthralgias
What are the debilitating arthralgias of alkaptonuria from?
homogentisic acid being toxic to cartilage
What are the 2 causes of albinism?
congenital deficiency of:
tyrosinase (inability to synthesize melanin) => AR
Defective tyrosine transporters (decrease amounts of tyrosine & melanin)
During embryology, what also may cause albinism?
lack of migration of neural crest cells
Describe the inheritance pattern of albinism
variable inheritance due to locus heterogeneity
ocular albinism is XLR
What are the 3 forms of homocystinuria? How are they inherited & what is result?
ALL are AR resulting in excess homocysteine & cysteine is now essential amino acid
Cystathionine synthase deficiency
Decreased affinity of cystathioinine synthase for pyridoxal phosphate
Homocysteine methyltransferase deficiency
How is Cystathionine synthase deficiency treated?
increase cysteine, B12 & folate, B6 in diet
How is Decreased affinity of cystathioinine synthase for pyridoxal phosphate treated?
increased a lot of vitamin B6 in diet