Amino Acid Metabolism Flashcards
What is the nitrogen balance?
The amount of nitrogen intake + the amount f nitrogen excreetion.
Ketogenic vs glucogenic amino acids
Ketogenic amino acids yield endproducts of AcCoA and AcAc.
Glucogenic aminoacids yield pyruvate or a member of the TCA cycle.
Therapeutic transamination in case of hyperammonemia? What is done?
Hyperammonemia occurs when nitrogen excretion is impaired.
A keto acid analogs are therapeutically incorporatedto patients.
Acids are then transaminated to formcorresponding amino acid
Pyridoxal phosphate?
Functional form of vitamin B6, coenzyme for transamination reactions, bound with schiff base to enzyme
What is glutamines main function?
To bind to toxic ammonia and transport it to the kidneys and liver.
Glutamine + H2O –> glutamate + NH3
Explain the major pathway of nitrogen transport following musle proteolysis.
I) Proteins get degraded to amino acids , transaminated to mainly alanine and glutamine. To get transported to liver or kidney when conditions of energy needed.
II) Branched chain amino acids –> most important source of fuel
III) Main destination is liver. Ammonia is released by glutaminase and glutamate dehydrogenase.
IV) Some glutamine and alanine is taken up by kidney, ammonia is released and excreted.
Explain the urea cycle?
Bicarbonate condenses with ammonia to form bicarbamoyl phosphate.
Bicarbomoyl phosphate reacts with ornithine to form citrulline. Rest of urea cycle happens in cytosol.
Aspartate adds seconds ammonia and citrulline becomes argininosuccinate. Aspartate is excreted as fumarate.
Argininosuccinate is cleaved to form arginine and fumarate.
Arginine is hydrolyzed to form ornithine and urea.
What happens to the fumarate that is excreted from the urea cycle?
It can enter mitohondria and be metabolized to oxaloacetate
Oxaloacetate can be converted as
I) aspartate to reenter urea cycle.
II) produce ATP
III) form glucose
Defects of enzymes in urea cycle almost always lead to?
Hyperammonemia and mental retardation.
Explain Nonketotic Hyperglycinemia?
Deficient glycine cleaving complex
What is tetrahydrofolate and why is it so important?
It is the reduced form of folic acid.
It is a cofactor in metabolism of amino acids such as: Methionine Histidine Tryptophan Serine Glycine
Phenylketoneuria???
I) Missing or deficient phenylalanine hydroxylase leads to genetic disease called phenylketonuria (PKU).
II) Mental retardation caused by elevated levels of phenylalanine, becomes akor donor of amino groupsin aminotransferase activity. And depletes neural tissue of alpha - ketoglutarate.
III) Absence of aketoglutarate in brain –> shuts down TCA cycle and associated rod of aerobic activity which is essentisl for normal brain development.
IV) Presence of phenylacetate in urine imparts mousy odour.
V) If diagnosed early, addition of tyrosine and restriction of phenylalanine an minimize extent of mental retardation.
Major pathway of metabolism of tyrosine?
Tyrosine–> p- Hydroxyphenylpyruvate –> homogentisate
Further oxidation leads to acetoacetate and fumarate.
Minor pathway of tyrosine metabolism?
Tyrosine –> DOPA –> Dopamine –> Norepinephrine –> Epinephrine
Tyrosinemia, explain?
Deficiency of tyrosine aminotransferase –> accumulation and excretion of tyrosine METABOLITES, no metabolites formed.
Symptoms: mental retardation, liver failure etc
