Exam 3 Lecture # 3 (AA metabolism) Flashcards
What are the Essential AA’s?
Essential AA’s:
Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine
Conditionally Essential AA’s
Conditionally Essential AA’s:
Arginine, Cystine, Tyrosine
What are the two ketogenic AA’s?
What does ketogenic mean?
Ketogenic AA’s: Leucine and Lysine
Ketogenic: can be converted to ketones
Where can the Ketogenic AA’s enter the metabolism cycle?
Where can the Glucogenic AA’s enter the cycle?
Ketogenic AA’s can enter as Acetyl CoA or as Acetoacetate
Glucogenic can enter as almost anywhere else:
Pyruvate, a-Ketoglutarate, Succinyl CoA, Fumarate, Oxa
Most AA’s are obtained from _____
The ____ found in macromolecules of the body comes from the diet, after it has gone from the atmosphere and become fixed as ___ by organisms and plants
Most AA’s are obtained from the diet
The nitrogen found in macros comes from the diet, after the nitrogen in the atmosphere has been fixed as ammonia by microorganisms and plants.
Explain what negative vs positive nitrogen balance means
Negative Nitrogen Balance: loss is greater than intake/ more N2 excreted than ingested,
Negative nitrogen balance occurs this occurs with diet defecient in essential AA’s, fever, fasting, and wasting disease
Positive Nitrogen balance: N2 intake more than losses, occurs in growing children, pregnant women, after surgery and trauma, and tissue repair
The body degrades/loses the equivalent of ___ of protein every day.
This loss must be replaced by dietary protein.
What is nitrogen excreted as?
The body degrades 55 g of protein everyday.
The 55g must be made up in the diet otherwise we will be in negative nitrogen balance.
Nitrogen is excreted as urea
Nonessential AAs are synthesized from _______
The ____ are enzymes that catalyze the transfer of an amino group
Usually, the AA acts as the ___ and the alpha keto acid acts as the _____
Nonessential AAs are synthesized from a-keto acid precursors by transfer of a preexisting amino group from another AA by aminotransferase
The aminotransferases or transaminases are enzymes catalyzing the transfer of an amino group, plus a protin and an electron pair from donor to acceptor
Usually, the AA acts as the donor, and the alpha keto acid acts as the receptor
Draw the diagram showing pyruvate to acetyl coA to the krebs cycle and show where each AA enters the pathway
What gets deaminated to form pyruvate?
ALANINE can be deaminated to form pyruvate
Fumarate is produced from….
Tyrosine phenylalanine and aspartate
AA’s are metabolized to intermediates of what three things?
AA’s are metabolized to intermediates of glycolysis and the TCA cycle, and acetyl coA in the liver.
Alanine gets ____ to form pyruvate
a-Ketoglutarate gets ____ to form glutamate
What enzyme does this reaction?
Alanine gets DEAMINATED to form pyruvate
a-Ketoglutarate gets transaminated to form glutamate
This over all rxn done by aminotransferase
Valine can be formed from what?
Valine can be formed from a-ketoisovalerate only when this compound is administered therapeutically
This is a therapy for hypoammoneumia
What two AA’s do not participate in the transamination reaction?
Threonine and Lysine do not participate in the transamination reaction.
What two AA’s are involed in most of the transamination reactions as intermediates?
Glutamate and alpha-ketoglutrate are involved in most of the transamination reactions as intermediates.
____ is a cofactor for aminotransferases
Pyridoxal Phosphate is a cofactor for aminotransferases
It is a vitamin B derivative
Measuring the releease of ______ is used diagnostically to determine tissue damage
Measuring the release of transaminase is used to determine tissue damage
Most common ones they look for are ALT (alanine transaminase) and AST (aspartate transaminase)
An increase in what is a sign of liver disease, hepatitis, MI, etc
An increase in glutamate, aspartate, alanine and their aminotransferases is a sign of those problems
All of the following are true of the enzyme AST except:
A. sometimes called Aspartate Aminotrasferse
B. can produce glutamate if NADPH and alpha ketoglutarate are substrates
C. can produce a-ketoglutarate and aspartate
D. can produce glutamate and oxaloacetate
B. is not true it cannot produce glutamate if NADPH and alpha keto glutarate are substrates.
the above explanation is talking about glutamate dehydrogenase
What is the key amino acid used for AA synthesis to avoid free ammonia
What is the “gateway AA”
Glutamate is the “gateway” between AAs and free ammonia.
In the liver ammonia is incorporated into glutamate by which enzyme?
_______ always serves as one of the AA’s in transaminations - gateway between amino groups of most AAs and free ammonia
Glutamate dehydrogenase is the enzyme that incorporates free ammonia into glutamate
Glutamate always serves as one of the AA’s in transmaminations
Draw the reaction diagram for glutamate dehydrogenase
Explain allosteric regulation of this pathway
GD is allosterically regulated by purine nucleotides
ADP and GDP increase degradation of glutamate to form alpha ketoglutarate
ATP and GTP increase synthesis of glutamate
What is the most abundant circulating AA
Most abundant circulating AA in the blood is GLUTAMINE
Glutamine acts as an ammonia transporter
Explain the reaction catalyzed by glutamine synthase
Glutamine synthetase:
Glutamate + NH4 + ATP —–> Glutamine and ADP
What happens in the kidney with respect to glutamine
In the kidney, glutamine gets turned into glutamate, freeing up NH3
This reaction is catalyzed by glutaminase
This allows NH3 to be excreted as urea
What is the function of aminotransferases
IN ALL CASES what is involved in those rxn’s
Aminotransferases: to produce new AAs or to produce carboskeleton for glucose or ketone bodies in production
IN ALL CASES: alpha-ketoglutarate and glutamate are involved and the cofactor is PP
_________ is a mechanism for all cells of the body to avoid free ammonia that is severely toxic
GLUTAMATE is a mechanism for all cells of the body to avoid free ammonia that is severely toxic. Incorporation by dehydrogenase that is regulated allosterically. Occurs when proteins are degraded
In the liver NH4 goes to ____
In other tissues____
In the liver NH4 goes to the urea cycle
In other tissues no urea cycle, so glutamate -> glutamine by glutamine synthase and transport to liver or kidney
When energy is needed, proteins in skeletal muscle get degraded and the AAs are transformed to _____ and _______
When energy is needed proteins in skeletal muscle get degraded and the AAs are transformed to glutamine and alanine
Most glutamine is transported to liver and kidney where it is converted to _____
Most glutamine is transfered is transported to the liver and kidney where it is converted into alanine and ammonia (alanine glucose cycle)
Where are urea and ammonia produced?
Where is ammonia from glutamate produced
Urea and ammonia are produced in the liver
Ammonia grom glutamate produced in kidney
If the muscle needs to export NH4 it will produce?
If the muscle wants to have glucose returned by the liver, the muscle will produce ____
If muscle needs to export NH4 it will produce glutamine
If the muscle wants to have glucose returned by the liver, the muscle will produce alanine (alanine will be transported to the liver, and then alanine can be turned into pyruvate, which can make glucose)
What are the fates of the amino acids?
Explain the reaction catalyzed by glutamate dehydrogenase
Glutamate dehydrogenase:
a-keto glutarate + NH4 + NADPH —–> glutamate + NADP
