Last lecture we discussed the structure of Amino Acids which has the alpha carbon
attached to 4 groups : Amino group (NH3 +),Carboxyl group (COO-),Hydrogen and R
group.
Today we will talk about new section of Amino Acid that deals with common
pathways and common structures between these A.A and how they get
metabolized. Our main concern is the Nitrogen of the Amino group because it is a
source of Nitrogen, and this nitrogen is going to be released as Ammonia (NH₃)
which is a very toxic compound, so we must be careful when we are dealing with
these compounds. Also we have to maintain this nitrogen in balance ( no increasing
or decreasing) because we need it in the synthesis of many other compounds not
only A.A .
֍ Transamination:
generally the transamination process is about
transferring an amino group(NH3+) from a nitrogen
containing compound to a certain recipient by a
certain Aminotransferase (AT). In the case of
transamination of AA, we transfer amino group
from the AA to α-ketoglutarate (recipient).
*When an AA loses its amino group, it still have its
carboxyl group, hydrogen and R group which is
called it α-keto acid.
Simply:
Amino Acid – Amino group = α-keto acid
*So (α-keto acid) is a product from the
transamination reaction.
^ each AA has its own α-keto acid due to the differences in the R groups.
^accordingly, there are different α-keto acids derived from different AA.
so, each aminotransferase (AT) is specific for one or few amino group donors.
*The common characteristic between the transamination of all
A.A is that they have the same recipient which is
α-ketoglutarate.
α-ketoglutarate
is a TCA’s cycle
intermediate.
, recall that the structure of α-ketoglutarate (5 carbons, 1 carbonyl group, 2
carboxylic groups) adding amino group to it → transforming it into GLUTAMATE
(AA)
What is the first step?
-Transfer the amino group from any amino acid to the α-ketoglutarate which
becomes Glutamate.
What will happen to the amino acid that lost its amino group?
-It will become α-ketoacid.
Alanine Amino Transferase (ALT) another name is Alanine Transaminase.
ALT transfers the amino group from Alanine to α-ketoglutarate which become
glutamate and the leftover of Alanine is called pyruvate (α-ketoacid of alanine is
pyruvate). pyruvate can be used as a gluconeogenesis intermediate. (See pic A)
Aspartate Amino transferase (AST) transfers the amino group of Aspartate to
α-ketoglutarate which becomes Glutamate, and the leftover of Aspartate is called
Oxaloacetate (oxaloacetate is the α-ketoacid of aspartate). oxaloacetate can be
used as a gluconeogenesis intermediate. (See pic B).
There are other enzymes for other amino acids that have the same mechanism, but we will focus on these
two enzymes (ALT & AST), because they have medical significance.
The reaction of ALT goes in both directions, forward and Actually, we are
backward(reversible), but it favours the forward direction converting all
which is the synthesis of glutamate and conversion of Alanine amino acids into
glutamate!
to pyruvate, so the amino group of the Alanine funnels
َ
( تتجمع (تتمركز وinto glutamate.
In this situation we are producing pyruvate by degrading
amino acids, and we are degrading them because we're in the
starvation situation to produce energy and provide gluconeogenesis with its own
intermediates (e.g., oxaloacetate and pyruvate).
The reaction of AST goes in both directions(reversible), but generally favors the backward
direction, so during AA catabolism AST transfers amino group from glutamate to
oxaloacetate forming aspartate.
In this situation we didn't degrade the Aspartate, we produced it, why is this happening?
attached to 4 groups : Amino group (NH3 +),Carboxyl group (COO-),Hydrogen and R
group.
Today we will talk about new section of Amino Acid that deals with common
pathways and common structures between these A.A and how they get
metabolized. Our main concern is the Nitrogen of the Amino group because it is a
source of Nitrogen, and this nitrogen is going to be released as Ammonia (NH₃)
which is a very toxic compound, so we must be careful when we are dealing with
these compounds. Also we have to maintain this nitrogen in balance ( no increasing
or decreasing) because we need it in the synthesis of many other compounds not
only A.A .
֍ Transamination:
generally the transamination process is about
transferring an amino group(NH3+) from a nitrogen
containing compound to a certain recipient by a
certain Aminotransferase (AT). In the case of
transamination of AA, we transfer amino group
from the AA to α-ketoglutarate (recipient).
*When an AA loses its amino group, it still have its
carboxyl group, hydrogen and R group which is
called it α-keto acid.
Simply:
Amino Acid – Amino group = α-keto acid
*So (α-keto acid) is a product from the
transamination reaction.
^ each AA has its own α-keto acid due to the differences in the R groups.
^accordingly, there are different α-keto acids derived from different AA.
so, each aminotransferase (AT) is specific for one or few amino group donors.
*The common characteristic between the transamination of all
A.A is that they have the same recipient which is
α-ketoglutarate.
α-ketoglutarate
is a TCA’s cycle
intermediate.
, recall that the structure of α-ketoglutarate (5 carbons, 1 carbonyl group, 2
carboxylic groups) adding amino group to it → transforming it into GLUTAMATE
(AA)
What is the first step?
-Transfer the amino group from any amino acid to the α-ketoglutarate which
becomes Glutamate.
What will happen to the amino acid that lost its amino group?
-It will become α-ketoacid.
Alanine Amino Transferase (ALT) another name is Alanine Transaminase.
ALT transfers the amino group from Alanine to α-ketoglutarate which become
glutamate and the leftover of Alanine is called pyruvate (α-ketoacid of alanine is
pyruvate). pyruvate can be used as a gluconeogenesis intermediate. (See pic A)
Aspartate Amino transferase (AST) transfers the amino group of Aspartate to
α-ketoglutarate which becomes Glutamate, and the leftover of Aspartate is called
Oxaloacetate (oxaloacetate is the α-ketoacid of aspartate). oxaloacetate can be
used as a gluconeogenesis intermediate. (See pic B).
There are other enzymes for other amino acids that have the same mechanism, but we will focus on these
two enzymes (ALT & AST), because they have medical significance.
The reaction of ALT goes in both directions, forward and Actually, we are
backward(reversible), but it favours the forward direction converting all
which is the synthesis of glutamate and conversion of Alanine amino acids into
glutamate!
to pyruvate, so the amino group of the Alanine funnels
َ
( تتجمع (تتمركز وinto glutamate.
In this situation we are producing pyruvate by degrading
amino acids, and we are degrading them because we're in the
starvation situation to produce energy and provide gluconeogenesis with its own
intermediates (e.g., oxaloacetate and pyruvate).
The reaction of AST goes in both directions(reversible), but generally favors the backward
direction, so during AA catabolism AST transfers amino group from glutamate to
oxaloacetate forming aspartate.
In this situation we didn't degrade the Aspartate, we produced it, why is this happening?
