Amino Acid Metabolism II

Question 1

serine and ______ are deaminated by the action of a single enzyme ______.

Answer 1

threonine

dehydratase

Question 2

__________ is always the coenzyme of deamination

Answer 2

pyridoxal phosphate

Question 3

urea cycle overview

Answer 3

NH4 is toxic byproduct of amino acid catabolism

so is converted to urea in liver and then excreted via urine

Question 4

ketogenic only amino acids

Answer 4

leucine

lysine

Question 5

both glucogenic and ketogenic amino acids

Answer 5

phenylalanine
tryptophan
tyrosine
threonine
isoleucine

Question 6

N-end rule

Answer 6

N-terminal AA identity determines rate of ubiquitination

Question 7

proteasome

Answer 7

an ATPase catalytic protein degrader

20S = proteolytic domain
19S = regulatory domain - top and bottom - control flow into catalytic domain

Question 8

direct deamination

Answer 8

serine and threonine only

• -dehydration removing h2o
• -add h2o back to remove NH4+ = deamination

serine deaminated = pyruvate

threonine daminated = a-ketobutyrate

Question 9

SGOT

Answer 9

catalyzes interconversion of aspartate and oxaloacetate

also called aspartate aminotransferase AST

Question 10

SGPT

Answer 10

catalyzes interconversion of alanine and pyruvate

also called alanine aminotransferase AlT

Question 11

glutamate dehydrogenase

Answer 11

causes release of ammonium ion

glutamate to a-ketoglutarate

Question 12

CPSI

Answer 12

carbamoyl Pi synthetase I

combines CO2 and NH3 = carbamoyl Pi
–uses 2ATP

this step commits it to the urea cycle

NAG is allosteric activator for CPSI

Question 13

ornithine and citrulline in urea cycle

Answer 13

they are nonproteinogenic amino acids

ortho moves into mito to combine w/ carbamoyl Pi = citrulline

citrulline is moved to cytoplasm

Question 14

aspartate in urea cycle

Answer 14

it donates NH3 at cost of 2ATP to citrulline

whats left = fumarate

the AA arginine is created

Question 15

creation of ornithine

Answer 15

created when urea is removed from arginine

Question 16

synthesis precursors

Answer 16

intermediates from 3 pathways

glycolysis
–3-PG, PEP, pyruvate

TCA
–a-ketoglutarate, OAA

PPP
–R5P, erythrose-5-Pi

Question 17

transamination rxns

Answer 17

1. by SGPT
   pyruvate/alanine exchange
2. by SGOT
   OAA/aspartate exchange
3. by glutamate dehydrogenase
   a-ketoglutarate/glutamate exchange

Question 18

aspartate fate

Answer 18

1. glutamine donates NH3 to it = asparagine
2. in other organisms it can be modified to create:
   lysine, methionine, threonine

Question 19

glutamate fates

Answer 19

glutamine is formed in cells as a way to transport free NH4+ to the liver

coupled rxns and cyclization = proline

glutamine reduced and transaminated = ornithine

Question 20

adenlylation

Answer 20

the addition of an AMP ribonucleotide

this inactivates glutamine synthetase

Question 21

uridylylation

Answer 21

the addition of UMP ribonucleotide

Question 22

3-PG derivaties

Answer 22

3 rxns to get to serine

vit B 6 or 12 can help remove side chain of serine = glycine

serine can be converted to cysteine

Question 23

______ is a catabolic intermediate of phenylalanine

Answer 23

tyrosine

Question 24

aromatic amino acids are derived from intermediates originating in the _____ ?

Answer 24

PPP

Question 25

histidine is synthesized from ?

Answer 25

ribose-5-Pi

Question 26

tryptophan, phenylalanine and tyrosine synthesis begins by ?

Answer 26

combining erythrose-4P and PEP to make chorismate

Question 27

branched amino acids are synthesized from ?

Answer 27

pyruvate

ex. valine, leucine, isoleucine

Question 28

list the AA derivatives:

1. glycine
2. glutamate
3. arginine
4. methionine
5. histidine
6. tryptophan
7. tyrosine

Answer 28

1. heme
2. glutathione, polyamines, GABA
3. NO, creatine Pi
4. SAM
5. histamine
6. serotonin
7. epinh/norepi, dopamine, melanins

Question 29

what is the difference btwn synthetases and synthases ?

Answer 29

synthEtases use ATP