Metabolism of phenylalanine and tyrosine
Summary
TLDRThis script delves into the metabolism of the aromatic amino acids phenylalanine and tyrosine by liver cells, highlighting their conversion into acetyl acetate and fumarate. These compounds serve as precursors for ketone bodies and glucose, respectively, demonstrating the dual role of these amino acids as both gluconeogenic and ketogenic. The detailed enzymatic processes, including the function of phenylalanine hydroxylase and tyrosine amino transferase, are outlined, culminating in the formation of essential fuel molecules for the body.
Takeaways
- 🌟 Phenylalanine and tyrosine are aromatic amino acids that can be metabolized by liver cells to form acetyl acetate and fumarate.
- 🔍 Acetyl acetate is used for ketone body formation, while fumarate is used for glucose production, making these amino acids both glucogenic and ketogenic.
- 🧬 The first step in the process involves converting phenylalanine to tyrosine, catalyzed by the enzyme phenylalanine hydroxylase.
- 🌀 Phenylalanine hydroxylase is a mixed function oxygenase, utilizing diatomic oxygen to form tyrosine and water.
- 💧 The enzyme requires tetrahydrobiopterin for its activity, which is synthesized from dihydrobiopterin with the help of NADPH and dihydrofolate reductase.
- ♻️ Dihydropyridine reductase regenerates tetrahydrobiopterin, allowing for its reuse in the reaction.
- 🔄 Tyrosine amino transferase, using PLP (pyridoxal phosphate), transfers the alpha amino group from tyrosine to an alpha keto acid, forming p-hydroxyphenylpyruvate.
- 🌀 p-Hydroxyphenylpyruvate dioxygenase removes a carbon dioxide molecule and adds both atoms of diatomic oxygen to the substrate, forming homogentisate.
- 🔄 Another dioxygenase, homogentisate 1,2-dioxygenase, further modifies the molecule to form allyl acetyl acetate.
- 🔄 An isomerase, using glutathione, converts allyl acetyl acetate into fumarate and acetyl acetate.
- 🌿 The final step cleaves the bond in acetyl acetate to form fumarate and acetyl acetate, which can be used for glucose and ketone body synthesis, respectively.
Q & A
What are the two aromatic amino acids discussed in the script?
-The two aromatic amino acids discussed in the script are phenylalanine and tyrosine.
How are phenylalanine and tyrosine related to glucose and ketone bodies?
-Phenylalanine and tyrosine are known as glucogenic and ketogenic amino acids because they can be metabolized to form both glucose and ketone bodies.
What is the first step in the metabolic pathway of phenylalanine and tyrosine?
-The first step is the transformation of phenylalanine into tyrosine, catalyzed by the enzyme phenylalanine hydroxylase.
What type of enzyme is phenylalanine hydroxylase?
-Phenylalanine hydroxylase is a mixed function oxygenase, which uses a diatomic oxygen molecule for the reaction.
What is the role of tetrahydrobiopterin in the first step of the metabolic pathway?
-Tetrahydrobiopterin provides the reducing power necessary for phenylalanine hydroxylase to catalyze the conversion of phenylalanine to tyrosine.
How is tetrahydrobiopterin synthesized in our cells?
-Tetrahydrobiopterin is synthesized from dihydrobiopterin in the presence of NADPH and an H+ ion, catalyzed by the enzyme dihydrofolate reductase.
What is the purpose of the enzyme dihydropyridine reductase in this metabolic pathway?
-Dihydropyridine reductase is used to regenerate tetrahydrobiopterin from its reduced form, using the reducing power of NADPH.
What enzyme is responsible for transferring the alpha amino group from tyrosine to an alpha keto acid?
-The enzyme responsible for this transfer is tyrosine aminotransferase, which uses pyridoxal phosphate (PLP) for the reaction.
What intermediate is formed after the removal of carbon dioxide from the substrate molecule in the metabolic pathway?
-The intermediate formed is homogentisate, after the carbon dioxide is removed and two oxygen atoms are attached to the substrate.
What type of enzyme is used to isomerize homogentisate to form fumarate and acetyl acetate?
-An isomerase enzyme, specifically homogentisate isomerize, is used to isomerize homogentisate to form fumarate and acetyl acetate.
What is the final product of the metabolic pathway for phenylalanine and tyrosine?
-The final products of the metabolic pathway are acetyl acetate and fumarate, which can be used to form ketone bodies and glucose, respectively.
Outlines
🔬 Metabolism of Phenylalanine and Tyrosine
This paragraph explains how the liver cells metabolize aromatic amino acids phenylalanine and tyrosine into acetyl acetate and fumarate. Acetyl acetate is used to form ketone bodies, while fumarate is used to form glucose, making these amino acids both glucogenic and ketogenic. The first step involves transforming phenylalanine into tyrosine using the enzyme phenylalanine hydroxylase, a mixed-function oxygenase, which uses diatomic oxygen and the reducing power of tetrahydrobiopterin.
🧪 Detailed Biochemical Process of Tyrosine Formation
The paragraph continues with the detailed biochemical process of forming tyrosine from phenylalanine. It describes how phenylalanine hydroxylase, aided by tetrahydrobiopterin and NADPH, catalyzes the conversion. The regeneration of tetrahydrobiopterin involves the enzyme dihydropyridine reductase. The next steps include the use of tyrosine amino transferase, pyridoxal phosphate (PLP), and several dioxygenase enzymes to form intermediate compounds like hydroxyphenylpyruvate and homogentisate, eventually leading to the formation of acetyl acetate and fumarate. These intermediates can be used for energy production in the form of ketone bodies and glucose.
Mindmap
Keywords
💡Aromatic amino acids
💡Phenylalanine
💡Tyrosine
💡Acetyl acetate
💡Fumarate
💡Phenylalanine hydroxylase
💡Tetrahydrobiopterin
💡Dihydrofolate reductase
💡Tyrosine amino transferase
💡PLP (Pyridoxal phosphate)
💡p-Hydroxyphenylpyruvate dioxygenase
💡Isomerase
💡Fumarate acetyl acetate
Highlights
The aromatic amino acids phenylalanine and tyrosine are discussed for their metabolic pathways in liver cells.
Phenylalanine and tyrosine are identified as glucogenic and ketogenic amino acids due to their ability to form glucose and ketone bodies.
The first step of the metabolic process involves the conversion of phenylalanine to tyrosine catalyzed by phenylalanine hydroxylase.
Phenylalanine hydroxylase is a mixed function oxygenase, utilizing diatomic oxygen for the conversion process.
The reducing power of tetrahydrobiopterin is essential for the catalytic activity of phenylalanine hydroxylase.
Tetrahydrobiopterin is synthesized by cells starting from dihydrobiopterin in the presence of NADPH and H+.
Dihydropyridine reductase is used to regenerate tetrahydrobiopterin for continuous use in the reaction.
Tyrosine amino transferase and PLP (pyridoxal phosphate) are involved in the transfer of the alpha amino group from tyrosine.
The formation of p-hydroxyphenylpyruvate occurs after the removal of the alpha amino group from tyrosine.
p-Hydroxyphenylpyruvate dioxygenase catalyzes the addition of both oxygen atoms from diatomic oxygen to the substrate molecule.
The intermediate compound homogentisate is formed after the removal of carbon dioxide.
A second dioxygenase, homogentisate 1,2-dioxygenase, is used to form the intermediate allyl-acetyl acetate.
An isomerase enzyme and glutathione activity are responsible for the isomerization of allyl-acetyl acetate to fumarate.
The final step involves the cleavage of a sigma bond by fumarate, resulting in the formation of acetyl acetate and fumarate.
Acetyl acetate can be used by parasites to form ketone bodies, while fumarate can be used to form glucose.
The metabolic pathways of phenylalanine and tyrosine are crucial for the production of fuel molecules in the body.
Transcripts
the next two amino acids that we're
going to focus on will be the aromatic
amino acids phenylalanine and tyrosine
and we're going to look at how our liver
cells can metabolize these two amino
acids ultimately forming acetyl acetate
and fumarate now acetyl acetate can be
used by our parasites to form ketone
bodies while fumarate can be used to
form glucose and that's exactly why
these two amino acids phenylalanine and
tyrosine are known as glucose anak and
ketogenic amino acids because we can use
them to ultimately form both glucose and
ketone bodies
let's begin by examining step one and
actually what step 1 shows us is we can
transform phenyl alanine directly into
tyrosine and this is precisely how our
cells can synthesize tyrosine by
beginning with phenyl alanine now the
enzyme that catalyzes step one is phenyl
alanine hydroxylase and this enzyme is
part of a category of enzymes we call
mixed function oxygen ASIS so this is a
mixed function oxygenase and what that
means is it uses a diatomic oxygen it
takes one of the oxygen atoms within
this diatomic molecule places it on this
reactant the phenyl alanine and this
basically forms the tyrosine and this
oxygen is shown here now the other
oxygen atom goes to form water
that's exactly why water is released
here so phenyl alanine hydroxylase is a
mixed function oxygenates now in order
for the phenyl alanine hydroxylase to be
able to catalyze this step it has to use
the reducing power of an electron
carrier molecule we call
tetrahydrobiopterin now
tetrahydrobiopterin is actually not a
vitamin because our cells can synthesize
this molecule and to synthesize this
molecule we basically begin with dye
hydro
by Opteron so in the presence of NADPH
and an H+ ion the enzyme dihydrofolate
reductase basically takes the dye Hydra
by op turan and transfers the reducing
power from NADPH on to this molecule to
give us tetrahydrobiopterin and then and
then this mixed function oxygenates this
enzyme phenylalanine hydroxylase uses
the reducing power of
tetrahydrobiopterin to basically form
tyrosine and of course we also use up
the reducing power of this molecule to
form Quinn a node dye hydra by operon
now to regenerate back the
tetrahydrobiopterin so that it can be
used again in this reaction we use an
enzyme called dihydropyridine reductase
and this enzyme takes the reducing power
of NADPH transfers it onto this molecule
to form back the tetrahydrobiopterin so
that again we can use the reducing power
of this molecule to undergo this first
step so again in the first step we
utilize a phenyl alanine a diatomic
water molecule we use NADPH to basically
give us this and by using the reducing
power of this molecule we transform the
phenyl alanine into tyrosine so one of
the oxygen atoms goes onto this ring of
the phenyl alanine and the other one is
used to form a water molecule now once
we form tyrosine what happens next well
next we basically have to use an amino
transferase to transfer the Alpha amino
group from tyrosine onto an alpha keto
acid and so we have the enzyme tyrosine
amino transferase and just like any mu
transferase this one has to use PLP so
pyridoxal phosphate we transfer this
alpha amino group from the tyrosine onto
an alpha key to glue direct now the
alpha ketoglutarate upon
seeing that amino group eform glutamate
upon removing the alpha immune agree
from tyrosine we form this alpha keto
acid the P hydroxy phenyl pyruvate now
once we form this molecule the next step
is to use a dioxygen ace and unlike an
oxygen ace where one of the oxygen atoms
was used to form water and the other
oxygen atom went on to the phenyl
alanine to form the tyrosine an enzyme
that we call dioxygen ace uses a
diatomic water a diatomic oxygen and it
uses both atoms of that diatomic oxygen
to attach it onto that substrate
molecule so in this step we basically
want to remove this carbon dioxide and
we want to use both of the oxygen atoms
and attach them onto this substrate to
basically form an intermediate we call
how magenta say so the enzyme that
catalyzes this step is P hydroxy phenyl
pyruvate dioxygenase and so ultimately
we attach an oxygen here onto this
carbon and the other oxygen goes onto
this ring here so now we have two oxygen
atoms here two oxygen atoms here and
this carbon dioxide group was basically
removed as carbon dioxide now in the
next step we want to use yet again a
dioxygen ace so now we use homogeneous
eight one two dioxygen ace again we use
a diatomic water a diatomic oxygen one
of the oxygen is basically attached onto
this carbon the other oxygen is attached
onto this carbon so ultimately we break
this Sigma bond and PI bond within this
ring we attach the oxygen here and here
to form this intermediate form allyl
acetyl acetate now in the next step we
basically want isomerize so we want to
transform this assist group into
a trans group so we have the Syst double
bond here but we want to form a trans
double bond as shown here so the enzyme
that catalyzes this step is an isomerase
so we have malleolus edo acetate
isomerize which uses the activity of
glutathione to basically form this
molecule the four fumarole
acetyl acetate and the final step in
this reaction in which we ultimately
want to cleave this Sigma bond here by
using essentially a water molecule this
is this is catalyzed by fumarole acetyl
acetate and so ultimately we form a
fumarate because once we cleave this
bond the oxygen essentially attaches
onto this carbon and this becomes a ch3
and so we form acetyl acetate and
fumarate and now this can be used to
form a ketone body and this can be used
to form our glucose so we see that
inside ourselves we can transform phenyl
alanine into tyrosine and so ultimately
we can basically form tyrosine within
this step and both phenyl alanine and
tyrosine by following these series of
steps can be transformed into these
carbon skeletons acetyl acetate and
fumarate and these can ultimately be
used to form fuel molecules so either
ketone bodies in this case or glucose
molecules in this case
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