Amino acid metabolism Flashcards
Which of the following statements is correct regarding glutamate?
a. In transamination, glutamate is produced when alpha-ketoglutarate accepts an amine group from another molecule.
b. Synthesis occurs when glutamine gains an amine group.
c. Glutamate is an important precursor of aspartate.
g. Glutamate is produced by the oxidation of arginine
a. In transamination, glutamate is produced when alpha-ketoglutarate accepts an amine group from another molecule.
What molecular change occurs during transamination?
a. Carboxylation accompanies addition of an amine group.
b. Decarboxylation
c. Carbons are exchanged between 2 molecules.
d. An amine group and a carbonyl group are exchanged.
e. The amine group on 1 molecule is exchanged with an amine group on another molecule.
d. An amine group and a carbonyl group are exchanged.
The conversion of glutamate to glutamine catalyzed by glutamine synthetase results in which of the following?
a. Production of ATP
b. Release of urea
c. Removal of ammonia
d. Phosphorylation of ADP
e. Production of a toxic product
c. Removal of ammonia
Which of the following compounds is not produced directly from arginine?
a. Nitric oxide
b. Citrulline
c. ADMA
d. Ammonia
e. Ornithine
d. Ammonia
Which of the following is true regarding the synthesis of proline? (Select all that apply).
a. Reduction of a carbonyl carbon is the last step.
b. It requires oxidation, reduction, phosphorylation, and dephosphorylation.
c. It involves a phosphorylated intermediate.
d. It includes a non-enzymatic step.
e. Cyclization requires a cyclizing enzyme.
b. It requires oxidation, reduction, phosphorylation, and dephosphorylation.
c. It involves a phosphorylated intermediate.
d. It includes a non-enzymatic step.
Synthesis pathways are grouped into 6 families according to common anabolic precursors
1/ alpha-ketoglutarate (glutamate family)
2/ Serine
3/ Aspartate
4/ Aromatic
5/ Histidine
6/ Pyruvate
Which essential amino acids contain aromatic rings?
Phenylalanine and tryptophan
Tyrosine a non-essential amino acid made from __ (which essential amino acid?)
Phenylalanine
What are the 3 amino acids produced from glutamate?
Arginine
Glutamine
Proline
Formula of transamination?
How is glutamate made?
By transamination
=> alpha - ketoglutarate + aspartate -> glutamate + oxaloacetate
Step of glumtamine synthesis
Made from glutamate using glutamine synthetase with the removal of ammonia
5 amino acids that inhibit glutamine synthetase
1/ Glycine
2/ Alanine
3/ Serine
4/ Histidine
5/ Tryptophan
2 nucleotides that inhibit glutamine synthetase
AMP
CTP
Formula of covalent regulation of glutamine synthetase
PROLINE SYNTHESIS
-> What are the 3 steps from glutamate?
1/ phosphorylation
2/ oxidation & dephospho rylation - necessary to produce cyclization intermediate (cyclization (non-enzymatic))
3/ Reduction
PROLINE SYNTHESIS
-> Identify
1/ Glutamate-5-semialdehyde
2/ 1-Pyrroline-5-carboxylic acid
3/ Proline
ARGININE SYNTHESIS
-> What are the 4 pathways to make it?
1/ Forward reaction (2 steps) from citrulline, ATP and aspartate
2/ Production from asymmetric dimethyl arginine (ADMD - a modified arginine in proteins)
3/ Reverse reaction (arginase) from ornithine
4/ A separate reaction from citrulline, nitric oxide, and NADP+
Why is arginine important in urea cycle?
For producing urea for excretion
Alpha-ketoglutarate family
-> What is happening at 1?
NADP+ -> NADPH + O2
Alpha-ketoglutarate family
-> What is happening at 1?
NADP+ -> NADPH + O2
Alpha-ketoglutarate family
-> What is happening at 2?
ATP -> AMP + 2Pi
Alpha-ketoglutarate family
-> What is happening at 3?
H2O
Which amino acid is the precursor of serine?
Glycine
Which of the following glycolysis intermediates is the closest precursor to serine?
a. 3-phosphoglycerate
b. Phosphoenolpyruvate (PEP)
c. Dihydroxyacetone phosphate (DHAP)
d. Pyruvate
e. 2-phosphoglycerate
a. 3-phosphoglycerate
Which of the following amino acids is serine most closely linked through folate metabolism?
a. Alanine
b. Glycine
c. Arginine
d. None of the above
e. Cysteine
b. Glycine
he deficiency of which enzyme leads to homocystinuria?
a. Transmethylase
b. S-adenosyl methionine hydrolase
c. Methionine adenosyltransferase
d. Cystathionase
e. Cystathionine β-synthase
e. Cystathionine β-synthase
Cystathionine is converted into cysteine and β-ketobutyrate by which enzyme?
a. Transmethylase
b. Methionine adenosyltransferase
c. S-adenosyl methionine hydrolase
d. Cystathionase
e. Cystathionine β-synthase
d. Cystathionase
Which amino acid is NOT part of the aspartate family?
a. Threonine
b. Cysteine
c. Methionine
d. Lysine
e. Asparagine
b. Cysteine
hich is true about the reaction catalyzed by asparagine synthetase? Select all that apply.
a. It produces AMP.
b. It involves pyruvate and alanine for transamination.
c. It produces ATP.
d. There is a high energetic cost.
a. It produces AMP.
d. There is a high energetic cost.
Which of the following reactions give rise to aspartate? (Select all that apply).
a. Transamination of selenocysteine
b. Asparagine hydrolysis
c. Transamination of oxaloacetate and glutamate
d. Folate metabolism
e. Cleavage of argininosuccinate in the urea cycle
b. Asparagine hydrolysis
c. Transamination of oxaloacetate and glutamate
e. Cleavage of argininosuccinate in the urea cycle
The hydroxylation of which amino acid is important for making strong collagen?
a. Methionine
b. Threonine
c. Serine
d. Lysine
e. Cysteine
d. Lysine
Methionine is produced from homocysteine by…?
a. …succinylation.
b. …adding a carboxyl group.
c. …adding a methyl group to the sulfur atom.
d. …loss of ammonium ion.
e. …phosphorylation.
c. …adding a methyl group to the sulfur atom.
The first 3 steps in the synthesis of threonine are the same as the first 3 steps in the synthesis of…?
a. …methionine.
b. …aspartate.
c. …lysine.
d. …serine.
a. …methionine.
Which of the following statements regarding lysine metabolism is NOT correct?
a. Lysine is one of the most posttranslationally modified amino acids.
b. The first 2 reactions in the synthesis of lysine, threonine, and methionine are the same.
c. The deficiency of alpha-aminoadipic semialdehyde synthase leads to low lysine levels in the blood.
d. Hyperlysinemia is the accumulation of lysine in the blood.
e. Alpha-aminoadipic semialdehyde synthase deficiency leads to hyperlysinemia.
c. The deficiency of alpha-aminoadipic semialdehyde synthase leads to low lysine levels in the blood.
Which is true of the aromatic amino acid family?
a. There are 10 aromatic amino acids.
b. The aromatic amino acid family includes phenylalanine, tyrosine, and threonine.
c. Each member is synthesized from phosphoenolpyruvate (PEP) and erythrose 4-phosphate.
d. The members of the aromatic amino acid family are synthesized primarily from neurotransmitters.
c. Each member is synthesized from phosphoenolpyruvate (PEP) and erythrose 4-phosphate.
The aromatic amino acid family is composed of…? (Select all that apply)
a. …phenylalanine.
b. …threonine.
c. …tryptophan.
d. …tyrosine.
e. …auxin.
a. …phenylalanine.
c. …tryptophan.
d. …tyrosine.
Which of the following is true regarding thyroid hormone metabolism? Select all that apply.
a. Triiodothyronine, with three iodines, is the most active form.
b. Thyroxine is the most active form.
c. All deiodinases contain selenium.
d. Iodide ions are imported into thyroid cells from the bloodstream.
e. All thyroid hormones contain zinc.
a. Triiodothyronine, with three iodines, is the most active form.
c. All deiodinases contain selenium.
d. Iodide ions are imported into thyroid cells from the bloodstream.
Which of the following is true regarding thyroid hormones?
a. Thyromodulin is necessary for the synthesis of thyroid hormones.
b. They are synthesized within the thyroid cells.
c. They are made from thyroglobulin, a precursor derived from glutamate.
d. They are derived from the breakdown of carbohydrates.
e. Thyroid hormones include thyroxine and triiodothyronine.
e. Thyroid hormones include thyroxine and triiodothyronine.
What is true regarding tyrosine catabolism dysfunction? Select all that apply.
a. It is a factor in phenylketonuria.
b. It is treated by reducing the intake of phenylalanine and tyrosine.
c. There are only two types of tyrosinemias.
d. It can result in black urine disease.
e. It can be managed by decreasing the intake of leucine.
a. It is a factor in phenylketonuria.
b. It is treated by reducing the intake of phenylalanine and tyrosine.
d. It can result in black urine disease.
Which amino acid is the main precursor of thyroid hormones?
a. Selenocysteine
b. Phenylalanine
c. Tyrosine
d. Lysine
e. Methionine
c. Tyrosine
Which enzyme converts thyroxine into triiodothyronine?
a. Aromatic acid decarboxylase
b. Dopamine-β-hydroxylase
c. Tyrosine transaminase
d. 4-fumaryl acetoacetase
e. Deiodinase
e. Deiodinase
hich of the following statements is NOT true?
a. There are two types of iodine-containing thyroid hormones: triiodothyronine (T3) and thyroxine (T4).
b. Alkaptonuria is a rare inherited genetic disorder in which the body breaks down tyrosine at very rapid rates and leads to the accumulation of fumarate and acetoacetate in the body.
c. Iodide ions, essential for the production of thyroid hormones, are grabbed from the blood and transported into the thyroid follicular cell via sodium-iodide symport.
d. The treatment of tyrosinemias and phenylketonuria involves the restriction of intake of amounts of tyrosine and phenylalanine in the individual’s diet.
e. Thyroglobulin protein participates in the synthesis of T4 and T3 hormones in the thyroid gland.
b. Alkaptonuria is a rare inherited genetic disorder in which the body breaks down tyrosine at very rapid rates and leads to the accumulation of fumarate and acetoacetate in the body.
Which of the following statements is NOT true?
a. There are two types of iodine-containing thyroid hormones: triiodothyronine (T3) and thyroxine (T4).
b. Alkaptonuria is a rare inherited genetic disorder in which the body breaks down tyrosine at very rapid rates and leads to the accumulation of fumarate and acetoacetate in the body.
c. Iodide ions, essential for the production of thyroid hormones, are grabbed from the blood and transported into the thyroid follicular cell via sodium-iodide symport.
d. The treatment of tyrosinemias and phenylketonuria involves the restriction of intake of amounts of tyrosine and phenylalanine in the individual’s diet.
e. Thyroglobulin protein participates in the synthesis of T4 and T3 hormones in the thyroid gland.
b. Alkaptonuria is a rare inherited genetic disorder in which the body breaks down tyrosine at very rapid rates and leads to the accumulation of fumarate and acetoacetate in the body.
Which of the following pairs is not correctly associated?
a. Tyrosinemia III—p-hydroxyphenylpyruvate dioxygenase deficiency
b. Tyrosinemia II—tyrosine transaminase deficiency
c. Alkaptonuria—homogentisate 1,2-dioxidase deficiency
d. Phenylketonuria—4-fumarylacetoacetase deficiency
e. Tyrosinemia I—4-fumarylacetoacetase deficiency
d. Phenylketonuria—4-fumarylacetoacetase deficiency
What are the 2 main pathways lead to serine?
1/ From 3-phosphoglycerate (connection to glycolysis)
2/ Exchanging carbon with glycine and folates (important for folate recycling)
A main path leading to serine is from 3-phosphoglycerate
-> Identify
A main path leading to serine is from 3-phosphoglycerate
-> Identify
A main path leading to serine is exchanging carbon with glycine and folates
-> Identify
1/ N5, N10 - methylene tetrahydrofolate
2/ Tetrahydrofolate
A main path leading to serine is exchanging carbon with glycine and folates
-> Identify
Serine
Methionine metabolism
-> Identify
Methionine metabolism
-> Identify
Methionine metabolism
-> Identify
Serine
What is homocystinura?
A genetic disease that caused by deficiency of cystathionine beta-synthase
3 ways to make aspartate
1/ Transamination
2/ Hydrolysis
3/ Urea cycle
How can aspartate be made from transamination?
How can aspartate be made from hydrolysis?
How can aspartate be made from urea cycle?
How is asparagine synthesized?
What is the enzyme involved in the synthesis of asparagine?
Asparagine synthetase
How is aspartate made from asparagine?
Identify the enzyme
Asparaginase
Methionine metabolism
-> Breakdown overlaps with ____ metabolism
Cysteine
Methionine metabolism
-> What are the 9 steps?
Methionine metabolism
-> Identify the enzyme
Betaine-homocysteine methyltransferase
Methionine metabolism
-> identify
Threonine metabolism
-> Identify
Phosphohomoserine
Threonine metabolism
-> identify
Hydroxylation of lysine is important for making ____
strong collagen
Aromatic family
-> identify
Aromatic family
-> Identify
Aromatic family
-> Identify
What are the 4 molecules made from tryptophan?
1/ Melatonin
2/ Niacin
3/ Serotonin
4/ Auxins
Role of melatonin
1/ Circadian rhythm sensing
2/ Affects mood, sleep, blood pressure
3/ Production affected by blue light
Role of serotonin
A neurotransmitter that can….
- causes vasoconstriction
- enhances memory/ learning
- contributes to happy feelings
Characteristics of niacin
Characteristics of auxins
Which enzyme catalyze this reaction?
PHE hydroxylases
The cause of phenylketonuria
Deficiency the the PHE hyroxylase enzyme
Identify
1/ Tetrahydrobiopterin
2/ Dihydrobiopterin
Tyrosine is a precursor of ___
catecholamines - L-dopa, L-dopamin, epinephrine, norepinephrine
Tyrosine forms radical in ____
ribonucleotide reductase
Tyrosine
-> Identify these 4 enzymes
1/ Tyrosine hydroxylase
2/ Aromatic amino acid decarboxylase
3/ Dopamin beta-hydroxylase
4/ Phenylethanoamine N-methyltransferase
Tyrosine
-> Identify
1/ Ascorbate
2/ Dehydroascorbate
Tyrosine
-> Identify
1/ S-adenosylmethionine
2/ S-adenosylhomocysteine
L-DOPA is a precursor to ___
dopamine
Which neurotransmitter synthesized from tyrosine is able to cross blood-brain barrier?
L-DOPA
Which neurotransmitter/hormone synthesized from tyrosine is able to cross blood-brain barrier?
L-DOPA
The role of Dopamine
A neurotransmitter
- inhibits norepinephrine release in blood vessels - acts as vasodilator
- reduced insulin production in pancreas
Tyrosine metabolism
-> Identify
1/ T4 (thyroxine)
2/ T3 (triiodothyronine)
Which amino acid is the most easily produced from pyruvate?
Alanine by transamination
Alanine metabolism
-> Which enzyme catalyze this reaction?
Alanine transaminase
The role of glucose-alanine cycle?
Important for removing ammonia
What can transamination in liver create?
Glutamate
Breakdown of glutamate can yield ___
amine for urea production
Alanine carries amine to ____
liver
What is the fate of pyruvate if there is a high concentration of ammonia?
It will undergo transamination to produce alanine
What is the fate of pyruvate if there is a low concentration of ammonia?
It will undergo reduction to produce lactate
How do Branches chain amino acids metabolism start with?
BCAAs (Leu, Val, Ile)
- start with decarboxylation and attachment of 2 carbon piece to Hydroxy-ethyl (TPP)
+) Val and Leu pathways involve attachment of 2 carbon piece to pyruvate
+) Isoleucine pathway involves attaching 2 carbon pieces to alpha-ketobutyrate
What are penultimate products? How do they become final products?
1/ alpha-ketoisocaproate (LEU)
2/ alpha-ketoisovalerate (bal)
3/ alpha-keto-beta-methylvalerate (ILE)
=> Each is transaminate to make final amino acid
Which enzyme involves in this reaction?
Threonine deaminase
Which BCAA inhibit threonine deaminase? Why?
Isoleucine will inhibit Threonine deaminase
-> because high ILE favors VAL & LEU
Which BCAA activates threonine deaminase? Why?
Valine will activate Threonine deaminase
-> because high VAL favors ILE
What is the starting material for ILE?
Alpha-ketobutyrate
What is the starting material for VAL & LEU?
Pyruvate
Breakdown of BCAAs occur through _____
The branched-chain alpha-keto acid dehydrogenase complex
What is the cause of maple syrup urine disease?
Mutations altering the branched-chain alpha-keto acid dehydrogenase complex
Histidine metabolism overlap nucleotide metabolism with ___ and ____
ribose-5-P & PRPP
What are the 3 categories of amino acid catabolism?
1/ Glucogenic - broken down to glycolysis/gluconeogenesis intermediates
2/ Ketogenic - broken down to acetyl-CoA
3/ Both - makes intermediates in both pathways
Which amino acids are ketogenic?
Lysine
Leucine
Which amino acids are either ketogenic and glucogenic?
Threonine
Tryptophan
Tyrosine
Phenylalanine
Isoleucine
Which amino acids are glucogenic?
Alanine
Cysteine
Glycine
Serine
Asparagine
Aspartate
Arginine
Histidine
Proline
Glutamate
Methionine
Valine
Catabolism of which amino acids lead to these diseases?
Catabolism of which amino acids lead to these diseases?
Catabolism of which amino acids lead to these diseases?
Catabolism of which amino acids lead to these diseases?
