Amino Acid Degradation and Synthesis Flashcards
What are termed Glucogenic or Glycogenic amino acids?
Amino acids whose catabolism yields pyruvate or one of the intermediates of the citric acid cycle are termed glucogenic or glycogenic. These intermediates are substrates for gluconeogenesis and, therefore can give rise to the net formation of glucose or glycogen in the liver and glycogen in the muscle.
What are ketogenic amino acids? What are the amino acids found in protein, that are exclusively ketogenic?
Amino acids whose catabolism yields either acetoacetate or one of its precursors (Acetyl coA or acetoacetyl coA) . Leucine and Lysine are the only exclusively ketogenic amino acids found in proteins.
Folic acid helps with the degradation of which amino acid? What happens when there is a deficiency?
Individuals deficient in folic acid excrete increased amounts of FIGLu in the urine, particularly after ingestion of a large dose of histidine. The FIGLu excretion test has been used in diagnosing a deficiency of folic acid.
What is the amino acid that form OAA?
Aspartate
What are the A.A. that can form alpha-ketoglutarate?
Glutamine, Proline, Arginine, Histidine “Go Practice Histo Again”
What amino acid form OAA?
Aspartate. Asparagine is hydrolyzed by asparaginase, liberating ammonia and aspartate.
What amino acids can form pyruvate?
Alanine, Serine, Glyicne, Cystine, Threonine
Deficiencies in the enzymes of phenyalanine and tyrosine metabolism lead to which diseases?
Phenylketonuria, and Alkaptonuria. Also albinism.
Methionine is an amino acid that can form from which TCA cycle derivative?
Succinyl CoA
After hydrolysis of SAM, Homocysteine can undergo two pathways, remethylation or transsulfication.
Explain the remethylated pathway
What vitamin do we need?
Homocysteine accepts a methyl group from N5-methltetrahydrofolate (N5-methul-THF) in a rx requiring methylcobalamin, a coenzyme derived from B12. The methyl group is transferred from the B12 derivative to homocysteine, and cobalamin is recharged from N5-methul-THF.
After hydrolysis of SAM, Homocysteine can undergo two pathways, remethylation or transsulfication.
Explain the transsulfication pathway
What vitamin is needed?
Homocysteine condenses with serine, forming cystathionine, which is hydrolyzed to alpha-ketobutyrate and cysteine.
This vitamin B6-requiring sequence has the net effect of converting serine to cysteine and homocysteine to alpha-ketobutyrate, which is oxidativly decarbaoxylated to form propionyl CoA.
what will happen if we have increase homocysteine levels?
What can be a treatment for this?
Rare deficiencies of what enzyme will cause increase levels of homocysteine?
Eleveations in plasma homocysteine levels promote oxidative damamge, inflammation, and endothelial dysfuction, and are an independent risk factor for occulise vascular disease.
Studies have shown that plasma homocysteine levels are inversely relatied to plasma levels of folate, B12, B6 - the three vitamins involved in the conversion of homocysteine to methionine or cysteine. Supplementation with these vitamins have been shown to reduce circulating levels of homocysteine.
Rare deficiencies in Cystathionine beta-synthase are seen in patients with classic homocystinuria. These individuals experience premature vascular disease.
Besides Methionine, what other 3 amino acids form Succinyl CoA?
How do these A.A. convert to Succinyl CoA?
Threonine, Valine and Isoleucine.
Valine and Isoleucine: are branched A.A. that generate propoinyl CoA, which is converted to Succinyl CoA by biotin and vitamin B12.
Threonine: gets dehydrated to alpha-ketoglutyrate, which is converted to propionyl CoA and then Succinyl CoA.
What are the 4 amino acids that give form to Acetyl CoA or Acetoacetyl CoA?
Leucine: exclusively ketogenic
Isoleucine: Keto and glucogenic
Lysine: exclusive ketogenic
Tryptopha: Gluco and Ketogenic
What are the 3d branched essential amino acids?
Where are these A.A. metabolized?
What are the 3 steps of their catabolism?
Isoleucine, Leucine, and Valine are essential amino acids. They are metabolized by the peripheral tissues (particularly muscle) rather than liver.
Their catabolism involves transamination, oxidative decarboxylation, and dehydrogenation.
What are pophyrin?
Porphyrins are cyclic compound (linkage of 4 pyrrole rings through methenyl bridges) that readily bind metal ions, usually Fe2+/Fe3+.
The most prevalent metalloporphyrin in humans is heme (prosthetic group for hemoglobin, myoglobin, and cytochromes, catalase, and tryptophan pyrrolase).
Only type III porphyrins are physiologically importain in humans.
Patient presents with urine that is red to brown in natural light, and has skin eruptions.
What disease related to A.A. specialized products can be?
Chronic porphyria: Porphyria cuatanea tarda, the most common porphyria, is a chronic disease of the liver and erythroid tissues. The disease is associated with a deficiency in uroporphyrinogen decarboxylase. Uroporphyrinogen III won’t be able to turn into coporporphyrinogen III which is a precursor of Heme.
Individuals with an enxyme defect leading to the accumulation of tetrapyrrole intermediates show photosensitivity, that is, their skin itche and burns (pruritis) when exposed to visible light. (superoxides damage membranes, and cause the release of destructive enzymes form lysosomes).
What is the heme degradation pathway?
What is the enzyme that participates on it?
Bilirubin Glucuronyl-transferase.
Takes bilirubin that entered the liver through Bilirubin-albumin complex, and coverts it to Bilirubin Diglucuronide.
If a pt. presents with Pyruvate kinase deficiency or glucose-6-dehydrogenase deficiency. How can this cause Jaundice?
Pt. will have massive lysis of RBCs and will produce bilirubin faster that what it can be conjugated in the liver. Hence pt. ends up with Hemolytic Jaundice.
