Lect 7, Amino Acid Metabolism

Question 1

Nitrogen Balance (Blood)
- NB = N intake - N loss
The biggest source of N is from ___ because it has _ nitrogens.
The other sources are ____ and ___ ____

Answer 1

Biggest N source = urea because it has 2 nitrogens

Others: Ammonia and uric acid

Question 2

The two major aminotransferases are ___ and ___.

Elevated levels of these in serum indicate ____

Answer 2

ALT (alanine aminotransferase) and AST (aspartate aminotransferase)

Elevated lvls indicate tissue damage

Question 3

Increased lvls of ALT indicate:

_______, _______, ______

Answer 3

Viral hepatitis, liver cell necrosis, and liver cancer

Question 4

Increased lvl of AST indicate:

______, ______, ______, and 6-8 hours after ____

Answer 4

Alcoholic cirrhosis, biliary cirrhosis, liver cancer, and 6-8 hours after an MI

Question 5

This is a rare autosomal disease cause by a deficiency in the enzyme BCKD. What is the disease, symptoms, and how you treat it?

Answer 5

Disease: Maple Syrup Urine Disease

Symptoms: urine smells like burnt maple syrup (due to presence of BC-AA’s)

Treatment is diet low in BC-AA’s (LIV = leu, ile, val)

Question 6

BCKD Enzyme Complex

• Requires 5 vitamin cofactors:
  1. _____
  2. ______
  3. _____
  4. _____
  5. ______

Answer 6

1. TPP
2. FAD
3. NAD
4. Lipoic acid
5. Coenzyme A

Question 7

Homocystinuria
-Risk factor for: ______

Two possible causes:

1. Vitamin deficiency in ____, ______, ____
   
   • defective enzyme: _______
2. ______________
   
   • defective enzyme: _______

Answer 7

Risk factor for: atherosclerotic heart disease

Two possible causes:

1. Vitamin deficiency in B6, B12, and Folate
   
   • Affects enzyme: homocysteine methyltransferase
2. Inherited genetic defect in the enzyme cystathionine Beta-synthase

Question 8

Ketogenic AA’s: ____ and ___

-Produce ____ _____, and cannot be precursors that make glucose

Answer 8

Ketogenic AA’s: Leu and Lys

-Produce ketone bodies

Question 9

Ketogenic and glucogenic AA’s: ___________

Answer 9

PITTT - Phe, Ile, Tyr, Trp, and Thr

Question 10

Tetrahydrobiopterin/Dihydrobiopterin/THB

• Defect in THB regeneration causes:
  1. ______ due to the problem in metabolism of ___ to ___

2. Disruption of production of ___, ___, ____ from ___ and ___

Clinical manifestation: _____

Answer 10

1. Secondary PKU (phenylketonuria) due to problem in metabolism of Phe to Tyr
2. Disruption of production of dopamine, NE, and 5-HT (serotonin) from Tyr and Trp

Clinical manifestation: severe neurological dysfunction due to disruption of AA xport to brain and myelin formation

Question 11

Albanism:

-Caused by a deficiency in ______, which converts ___ to ____

Answer 11

Def in tyrosinase, which converts Tyr to melanin

Question 12

Tyrosone Catecholamine Pathway:

Answer 12

Tyr –> Dihydroxyphenylalanine (dopa) –> Dopamine –> NE –> Epinephrine

Question 13

____ and ____ degrade Dopamine and NE into ___ and ____, respectively

High levels of these in urine can be diagnostic of: ____

Answer 13

MAO and COMT degrade Dopamine and NE into HVA and VMA, respectively

High levels of these in urine can be diagnostic of: pheochromocytoma (adrenal gland tumor)

Question 14

Thyroglobulin - made by ______ __ of thyroid gland and contain 120 __ residues.

Thyroglobulin helps produce the hormones __ and __

Answer 14

Thyroglobulin - made by follicular cells of thyroid gland and contain 120 Tyr residues.

Thyroglobulin helps produce the hormones T3 (diodotyrosine + monoiodotyrosine) and T4 (diodotyrosine + diodotyrosine)

Question 15

Glutathione - Glu/Cys/Gly complex

-Inhibited by ______ overdose, which increases levels of GGT (gamma-glutamytransferase) = ________ dysfunction

Answer 15

Inhibited by acetaminophen overdose, which increases levels of GGT (gamma-glutamytransferase) = hepatobiliary dysfunction

Question 16

Urea Cycle:
-Problem with enzyme ____ ____ causes Hyperammonemia.

-Final step is to use water to convert ___ to ____, releasing ____.

This is why a high ____ diet will increase ____ production.

_____ is cycled out of the brain to recreate carbamoyl phosphate

Answer 16

Urea Cycle:
-Problem with enzyme ornithine transcarbamoylase causes Hyperammonemia.

-Final step is to use water to convert Arg to Ornithine, releasing Urea.

This is why a high protein diet will increase urea production.

Ammonia is cycled out of the brain to recreate carbamoyl phosphate