Lecture 31 - Amino acids as fuel molecules

Question 1

Deamination of amino acids

Answer 1

Process to take the amino part off the amino acid to just get the carbon skeleton to be used for energy

Question 2

Deamination generates…

Answer 2

A carbon skeleton and a free amino acid group

Question 3

A carbon skeleton

Answer 3

One of the generations of deamination
Can be used for energy capture (catabolic reactions)
Can be used as a fuel molecule

Question 4

A free amino group

Answer 4

One of the generations of deamination

Generally excreted because it can’t be used as a fuel molecule

Question 5

Some amino acids can be deaminated by releasing ….

Answer 5

Some amino acids can be deaminated by releasing their amino groups to solution
e.g. glutamate deamination catalysed by glutamate dehydrogenase (GDH) - amino group is cleaved off glutamate to make alpha-ketoglutarate (the amino group is relpaced with a ketone group

There are only a few amino acids that this reaction can happen for

Question 6

Some amino acids are deaminated by transferring …

Answer 6

Some amino acids are deaminated by transferring their amino group to a veto acid
Known as a transamination - getting amino group and putting it on to another molecule
Catalysed by aminotransferase enzymes (transmainases)
It is reversible

Glutamate and alpha keto acid via glutatmate aminotransferase to alpha-ketoglutarte and alpha-amino acid

This transfer does not actually happen directly so for these reactions need a coenzyme called pyridoxal phosphate

Question 7

Pyridoxal phosphate

Answer 7

Pyridoxal phosphate is a coenzyme required for transamination reactions
Derived from vitamin B6
Carries - amino group (from the amino acid to the keto acid) - because it is not a straight swap between the 2 carbon skeletons

Exisits in 2 forms
Pyridoxal phosphate - no amino group
Pyridoxamine phosphate - with amino group

Transamination reactions involve 2 steps

Question 8

Pyridoxal phosphate vs pyridoxamine phosphate

Answer 8

Exisits in 2 forms
Pyridoxal phosphate - no amino group
Pyridoxamine phosphate - with amino group

Question 9

Transamination occurs in how many steps?

Answer 9

Two

Question 10

Transamination first step

Answer 10

Amino group is transferred from the amino acid to the pyridoxal phosphate (carbon skeleton is now the keto acid)

Amino group on the amino acid and the aldehyde group (O=C-H) on the pyridoxal phosphate interact with each other to form a Schiff base. Then as a result of this we have our amino group moved from the amino group to the coenzyme so it is now pyridoxine phosphate

Question 11

Transamination second step

Answer 11

Amino group is transferred to pyridoxine phosphate to the keto acid

Question 12

2 ways of deaminating the amino acid

Answer 12

First is directly in solution OR by doing transamination

Question 13

Common amino acid/keto acid pairs in metabolism

Answer 13

Amino acid  keto acid 
Glutamate  alpha-ketoglutarate (5C intermediate in CAC) 
Aspartate  oxaloacetate (4C molecule we start and finish with in the citric acid cycle) 
Alanine  pyruvate (this is the end product of glycolysis) 

Can feed all of these carbon skeletons into a metabolic pathway

Question 14

Glutamate ->

Answer 14

Alpha-ketoglutarate

Question 15

Aspartate ->

Answer 15

Oxaloacetate

Question 16

Alanine ->

Answer 16

Pyruvate

Question 17

Alpha-ketoglutarate ->

Answer 17

Glutamate

Question 18

Oxaloacetate ->

Answer 18

Aspartate

Question 19

Pyruvate ->

Answer 19

Alanine

Question 20

Keto acids can be fed into the metabolic pathways

Answer 20

Some ket acids can directly enter metabolic pathways, some keto acids require modification first

Question 21

Keto acids and metabolic pathways transamination reactions are also required to do what ….

Answer 21

Required to remove excess nitrogen via the liver (also to get the carbon skeleton)