Lecture 6 - Nitrogen Metabolism Part 2 Flashcards
when does amino acid catabolism occur
- Excess protein is consumed (high protein diet)
- Insufficient dietary protein (Kwashiorkor)
- Insufficient dietary energy (starvation)
what happens to carbon backbones and amino groups in amino acid catabolism
carbon skeletons enter the main energy pathways and amino groups are processed to urea in the liver for excretion
what is another word for aminotransferase
Transaminase
what is the co factor that is very important for the function of transaminase enzyme
pyridoxal phosphate
what vitamin is pyridoxal phosphate derived from
vitamin B6
where is pyridoxal phosphate found in the transaminase enzyme
Pyridoxal phosphate is found in the active centre of the transaminase enzyme
what is pyridoxamine phosphate
when the amino group from the amino acid has been transferred to the pyridoxal phosphate
once the amino group has been transferred and pyridoxamine phosphate has been formed, what will then occur
that amino acid will be transferred to another keto acid and will form new a-amino acid based off what the keto acid was
what part of the body has the highest concentrations of aminotransferases
the liver
what is the corresponding keto acid to aspartate
oxaloacetate
what is the corresponding keto acid to alanine
pyruvate
what is the corresponding keto acid to glutamate
a-ketoglutarate
what is a characteristic of aminotransferase reactions and what do they depend on
Reactions are reversible and dependent on concentration of substrates
aminotransferases are specific for what and what does that mean (use alanine as an example)
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
what do most aminotransferases only accept as their donor keto acid
αketoglutarate or oxaloacetate
what catalyses the reaction of glutamate to glutamine
glutamine synthase
why is glutamine a very efficient molecule in terms of transferring nitrogen
it can carry two amine groups
how many steps are required in the process of deamination of glutamine
two step process
what is the opposite reaction to glutamate > glutamine, and where is it important
glutamine > glutamate
important in the liver
what enzyme hydrolyses glutamine back to glutamate
Glutaminase enzyme
how is glutamate deaminated and what by
oxidatively deaminated by glutamate dehydrogenase
unlike other enzymes, what can glutamate dehydrogenase use to deaminate glutamate
NAD and NADP
why is the deamination of glutamate in the liver very important
for releasing ammonia in the liver, so that it can be used to make urea
what are the three ways that amino groups can be removed
- transamination
- oxidative deamination
- hydrolysis
what is an example of oxidative deamination to remove amino group
glutamate dehydrogenase
what is an example of hydrolysis to remove an amino group
glutaminase
what will the glutamine synthetase catalysed reaction produce
glutamine
in the process of removing nitrogen from the body what will happen to the glutamine that is produced in the glutamine synthetase catalysed reaction
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
what reaction will the glutamine undergo in the liver to produce glutamate and release what
Glutamine will then undergo the glutaminase reaction in the liver, releasing an ammonia group and forming glutamate
what reaction can glutamate undergo to release its remaining amino group in the liver
Glutamate can also undergo the glutamate-dehydrogenase reaction to release its remaining ammonia group
what amino acid is prominently formed in muscle and why
alanine due to higher levels of pyruvate
what will alanine get converted back to in the liver and what will happen to its nitrogen group
alanine will get converted back to pyruvate
its nitrogen group will be transferred to a-ketoglutarate which will form glutamate
What would be the likely product from the activity of glutamine synthetase under conditions of high ammonium ions (NH4 +)
- glutamine
What would be the likely product from the activity of glutamate dehydrogenase under conditions of high ammonium ions
glutamate
