Lecture 6 - Nitrogen Metabolism Part 2

Question 1

when does amino acid catabolism occur

Answer 1

Excess protein is consumed (high protein diet)

Insufficient dietary protein (Kwashiorkor)

Insufficient dietary energy (starvation)

Question 2

what happens to carbon backbones and amino groups in amino acid catabolism

Answer 2

carbon skeletons enter the main energy pathways and amino groups are processed to urea in the liver for excretion

Question 3

what is another word for aminotransferase

Answer 3

Transaminase

Question 4

what is the co factor that is very important for the function of transaminase enzyme

Answer 4

pyridoxal phosphate

Question 5

what vitamin is pyridoxal phosphate derived from

Answer 5

vitamin B6

Question 6

where is pyridoxal phosphate found in the transaminase enzyme

Answer 6

Pyridoxal phosphate is found in the active centre of the transaminase enzyme

Question 7

what is pyridoxamine phosphate

Answer 7

when the amino group from the amino acid has been transferred to the pyridoxal phosphate

Question 8

once the amino group has been transferred and pyridoxamine phosphate has been formed, what will then occur

Answer 8

that amino acid will be transferred to another keto acid and will form new a-amino acid based off what the keto acid was

Question 9

what part of the body has the highest concentrations of aminotransferases

Answer 9

the liver

Question 10

what is the corresponding keto acid to aspartate

Answer 10

oxaloacetate

Question 11

what is the corresponding keto acid to alanine

Answer 11

pyruvate

Question 12

what is the corresponding keto acid to glutamate

Answer 12

a-ketoglutarate

Question 13

what is a characteristic of aminotransferase reactions and what do they depend on

Answer 13

Reactions are reversible and dependent on concentration of substrates

Question 14

aminotransferases are specific for what and what does that mean (use alanine as an example)

Answer 14

aminotransferases are specific for the donor amino acid,

example: alanine aminotransferase (ALT) primarily catalyzes the transfer of an amino group from alanine to a keto acid

Question 15

what do most aminotransferases only accept as their donor keto acid

Answer 15

αketoglutarate or oxaloacetate

Question 16

what catalyses the reaction of glutamate to glutamine

Answer 16

glutamine synthase

Question 17

why is glutamine a very efficient molecule in terms of transferring nitrogen

Answer 17

it can carry two amine groups

Question 18

how many steps are required in the process of deamination of glutamine

Answer 18

two step process

Question 19

what is the opposite reaction to glutamate > glutamine, and where is it important

Answer 19

glutamine > glutamate

important in the liver

Question 19

what enzyme hydrolyses glutamine back to glutamate

Answer 19

Glutaminase enzyme

Question 20

how is glutamate deaminated and what by

Answer 20

oxidatively deaminated by glutamate dehydrogenase

Question 21

oxidatively deaminated by glutamate dehydrogenase

Answer 21

NAD and NADP

Question 22

why is the deamination of glutamate in the liver very important

Answer 22

for releasing ammonia in the liver, so that it can be used to make urea

Question 23

what are the three ways that amino groups can be removed

Answer 23

1- transamination
2- oxidative deamination
3- hydrolysis

Question 24

what is an example of oxidative deamination to remove amino group

Answer 24

glutamate dehydrogenase

Question 25

what is an example of hydrolysis to remove an amino group

Answer 25

glutaminase

Question 26

what will the glutamine synthetase catalysed reaction produce

Answer 26

glutamine

Question 27

in the process of removing nitrogen from the body what will happen to the glutamine that is produced in the glutamine synthetase catalysed reaction

Answer 27

Glutamine will be secreted from the tissue and then found in the blood stream and by amino acid transporters it will be taken up the liver

Question 28

what reaction will the glutamine undergo in the liver to produce glutamate and release what

Answer 28

Glutamine will then undergo the glutaminase reaction in the liver, releasing an ammonia group and forming glutamate

Question 29

what reaction can glutamate undergo to release its remaining amino group in the liver

Answer 29

Glutamate can also undergo the glutamate-dehydrogenase reaction to release its remaining ammonia group

Question 30

what amino acid is prominently formed in muscle and why

Answer 30

alanine due to higher levels of pyruvate

Question 31

what will alanine get converted back to in the liver and what will happen to its nitrogen group

Answer 31

alanine will get converted back to pyruvate

its nitrogen group will be transferred to a-ketoglutarate which will form glutamate

Question 32

What would be the likely product from the activity of glutamine synthetase under conditions of high ammonium ions (NH4 +)

Answer 32

glutamine

Question 33

What would be the likely product from the activity of glutamate dehydrogenase under conditions of high ammonium ions

Answer 33

glutamate