7B-Synthesis/Degredation of AA's

Question 1

What amino acids are considered to be essential?

Answer 1

PVT TIM HALL. Phe, Val, Trp, Thr, Ile, Met, His, Arg, Leu, Lys

Question 2

Which AA’s are strictly ketogenic?

Answer 2

Leu and Lys

Question 3

Which AA is essential for growth only in children?

Answer 3

Arg

Question 4

Why is tetrahydrofolate needed for AA synthesis?

Answer 4

FH4 is used to transfer one-carbon groups at various oxidation states
FH4 is used in AA degradation (serine and histidine)
FH4 is used in biosynthesis: glycine  serine

Question 5

Why is BH4 needed for AA synthesis?

Answer 5

BH4 is used for hydroxylation reactions (phenylalanine and tyrosine)

Question 6

What is the cause and Sx of Gly Metabolism disorder?

Answer 6

Lack of transaminase that converts glyoxylate –> glycine
Glycine is metabolized to glyoxylate.
Glyoxylate can be oxidized to Oxalate, which is not very soluble and can precipitate with Ca in the kidneys causing stones

Question 7

What is the cause of cystaionuria?

Answer 7

Defect in cystathionase

Deficiency in Vitamin B6 (PLP).

Question 8

What are the clinical manifestations of homocystinuria?

Answer 8

Cardiovascular disease/atherosclerosis (peroxiadtion of LDL), defective collagen synthesis, brain szrs/mental retardation.

Question 9

What is the cause of homocystinuria?

Answer 9

Primary: defect in cystathionine synthase (rare)
Secondary: deficiency in Vitamin B6, B12, or Folic Acid (more common)

Question 10

What is the cause and Sx of cystinuria?

Answer 10

Manifestation: Kidney Stones
Cause: a defect in the cystine transporter located in both the intestinal and renal cells.

Question 11

What is the cause and Sx of cystinosis?

Answer 11

Cause: a defect in the cystine transporter located in lysosomal membranes.
cystine crystals accumulate in lysosomes, disturb their function, and cause renal failure.

Question 12

What is the cause of maple syrup urine disease?

Answer 12

Caused by a deficiency in a-keto dehydrogenase activity, a deficiency in thiamine can accelerate this disorder (alcoholics).

Question 13

What are the Sx of maple syrup urine disease?

Answer 13

Manifestation: urine smells like maple syrup or burnt sugar

Ketoacidosis, and neurologic complications

Question 14

What are the Sx of PKU?

Answer 14

Manifestation: Accumulated phenylalanine and phenylketones are neurotoxic and lead to mental retardation
this inhibits the neuronal uptake of tyrosine & tryptophan, which are needed as neurotransmitter substrates and inhibits myelination of nerves

Question 15

What is the cause of PKU?

Answer 15

Cause: deficiency in Phenylalanine Hydroxylase activity, which may be due to:
one of 170 mutations in the PAH gene
deficiency in BH4 synthesis
deficiency in BH4 reductase activity

Question 16

What is the cause of alcaptonuria?

Answer 16

Cause: defect is in the enzyme Homogentisate Oxidase, therefor homegentisate accumulates and autooxidizes.
oxidized homogentisate makes urine black
binds and hyperpigments connective tissues and joints (ochronosis) resulting in arthritic joint pain

Question 17

What are the Sx and cause of tyrosinemia I?

Answer 17

Manifestation: liver failure and early death
Cause: defective Fumarylactoacetate Hyrdolase

Question 18

What are the Sx and cause of tyrosinemia II?

Answer 18

Manifestation: eye and skin lesions, & neurological problems
Cause: defective Tyrosine Aminotransferase

Question 19

What are the nonessential AA’s that can be made from intermediates of glycolysis?

Answer 19

Glycine, Serine, Cysteine and Alanine (Ala is major gluconeogenic AA) are all non-essential AA that can be formed from intermediates during glycolysis.

Question 20

What 5 amino acids can be made form a-KG?

Answer 20

Glutamate, Glutamine, Proline, Arginine, Histidine

Question 21

What 2 amino acids can be made from OAA?

Answer 21

Aspartate, Asparginine

Question 22

What 3 amino acids can be made form fumerate?

Answer 22

Aspartate, Phenylalanine, Tyrosine

Question 23

What 4 amino acids can be made from succinyl CoA?

Answer 23

Methionine, Threonine, Valine, Isoleucine

Question 24

What 6 amino acids can be made from pyruvate?

Answer 24

Threonine, Glycine, Tryptophan, Alanine, Serine, Cysteine

Question 25

what are some causes and Sx of homocystinuria?

Answer 25

disorders in the metabolism of homocysteine
inherited as autosomal recessive
high plasma and urinary levels of homocysteine and methionine and low levels of cysteine
defect in cystathionine β-synthase is the most common cause of homocystinuria
homozygotes exhibit ectopia lentis (displacement of the lens of the eye), skeletal abnormalities, premature arterial disease, osteoporosis, and mental retardation.
treatment includes restriction of methionine intake and supplementation with vitamins B6, B12, and folate.

Question 26

how can vitamin deficiencies in folate vitamin B12 or vitamin B6 can lead to homocysteinuria?

Answer 26

Folate provides FH4
Vitamin B6 provides PLP
Vitamin B12 is used as B12