Amino Acids

Question 1

Describe how you get from phenylalanine to epinephrine.

Answer 1

phenylalanine–>tyrosine via phenylalanine hydroxylase, requires BH4
tyrosine–>DOPA via tyrosine hydroxylase, requires BH4
(note: dopa–>melanin via tyrosinase)
DOPA–>dopamine via dopa decarboxylase Vit B6
dopamine–>NE, requires Vit C
NE–>Epi SAM

Question 2

Which enzyme does carbidopa inhibit?

Answer 2

dopa decarboxylase

Question 3

Cortisol stimulates which step?

Answer 3

NE–>Epi

Question 4

What are the breakdown products of dopamine, NE, and epinephrine?

Answer 4

dopamine–>homovanillic acid
NE–>VMA
epi–>metanephrine

Question 5

What are the essential amino acids?

Answer 5

Private (PVT) TIM HaLL
Phenylalanine
valine
threonine
tryptophan
isoleucine
methionine
histidine
leucine
lysine
**must eat!

Question 6

What are the acidic AA? Basic AA?

Answer 6

Acid AA: aspartate, glutamate

Basic AA: Arginine, Lysine, Histidine

Question 7

What are the charges of the basic AA?

Answer 7

(+) except for histidine which is neutral

Question 8

What are the functions of the basic AA?

Answer 8

periods of growth ARG and HIS
histones (bind neg. charge of DNA) ARG and LYS
nuclear localization signals

Question 9

What is arginine transformed into?

Answer 9

urea
creatinine
nitric oxide (w/ BH4)

Question 10

What is tryptophan converted into?

Answer 10

niacin–>NAD+ (B6)

serotonin (B6, BH4)–>melatonin

Question 11

What is histidine converted into?

Answer 11

histamine (Vit b6)

Question 12

What is glycine converted into?

Answer 12

porphyrin–>heme (B6)

Question 13

What is glutamate converted into?

Answer 13

GABA (B6).

Glutathione

Question 14

Where does the urea cycle take place?

Answer 14

hepatocytes

CPSI in mitochondria. Then carbamoyl phosphate transferred into cytosol for rest of urea cycle.

Question 15

What is a commonly deficient enzyme of the urea cycle?

Answer 15

orthinine transcarbamylase.

carbamoyl phosphate + ornithine–>citrulline.

Question 16

Describe the features of ornithine transcarbamylase deficiency.

Answer 16

X-linked recessive
Hepatic Encephalopathy (b/c of buildup of ammonium)
orotic acid in blood & urine
BUN decreased b/c can’t make urea

Question 17

2 causes of hepatic encephalopathy?

Answer 17

b/c of increased ammonia

1. liver failure
2. OTC deficiency (urea cycle)

Question 18

What are the features of hepatic encephalopathy?

Answer 18

slurring speech
somnolence
vomiting
cerebral edema
blurred vision

Question 19

What is the treatment for ornithine transcarbamylase deficiency?

Answer 19

low protein diet
phenylbutyrate or benzoate (increase excretion of AA)
biotic (stimulates OTC)