CR III - Metabolism of Amino Acids Flashcards
(31 cards)
What are 5 that are essential for deriving coenzymes from for amino acid metabolism?
Vit B6 Folic acid B12 Biotin Niacin
What are the 9 (10) essential AA?
P - phenylalanine V - valine T - threonine T - tryptophan I - isoleucine M - methionine H - histidine A - arginine (children only) L - leucine L - Lysine
What is tyrosine synthesized from? Cysteine?
Tyrosine - synthesized from phenylalanine
Cysteine - synthesized from methionine
What do most transaminases require, one for each direction, of the reversible reaction?
Alpha-ketoglutarate (when converting AA to a-keto acid)
Glutamate - (when converting a-keto acid to AA)
What do all transaminases require as a prosthetic group? What is this derived from?
Pyridoxal phosphate
Derived from Vit B6
What are the only two AA that are not substrates for reversible transamination?
Lysine
Threonine
What are glycogenic AA? Ketogenic?
Glycogenic - AA whose carbon skeleton can be converted to glucose
Ketogenic - AA whose carbon skeletons can be converted into ktone bodies or acetyl Co-A (but not glucose)
Can AA be both ketogenic and glycogenic?
Yes
What are the two intermediates of the TCA cycle that can be used as the carbon skeletons for AA? Which AA can each produce? (One has 4, one has 2)
Alpha-ketoglutarate - glutamate, glutamine, proline, arginine
Oxaloacetate - aspartate, asparagine
Which two essential amino acids each act as a carbon skeleton for 2 other AA? Which ones?
Phenylalanine - tyrosine
Methionine - cysteine
What quantitatively is the most important glycogenic AA?
Alanine
How is asparagine made from aspartate? How is it converted back to aspartate? Are they glycogenic, ketogenic, or both?
Aspargine synthase and glutamine are needed to convert aspartate to asparagine
Asparaginase is used to catabolize asparagine to aspartate
Both are glycogenic
What types of AA are valine, leucine, and isoleucine? What end products are created by each (one for valine, 2 for each of the others)? Are each glycogenic, ketogenic, or both?
Branched AA
Valine - propionyl CoA - glycogenic
Leucine - acetoacetate and acetyl CoA - ketogenic
Isoleucine - propionyl CoA and acetyl CoA - both
What two enzymes are involved in converting valine, leucine, and isoleucine to their end products? Deficiency in which one results in MSUD?
AA transaminase
A-keto acid dehydrogenase
What is propionyl CoA converted to so it can enter the TCA cycle? What enzyme in this process requires a cofactor derived from B12?
Succinyl CoA
Methylmalonyl Mutase
Besides serines ability to come from are be metabolized to 3-phosphoglycerate, what two other products can it form? What do both require?
Pyruvate
Glycine
Both require pyridoxal phosphate
To make glycine, what does serine need besides pyridoxal phosphate? What is this a metabolite of? What is it involved in?
Tetrahydrofolate (THF)
Metabolite of folic acid
Involved in one carbon metabolism
What are three end products for Threonine? Which one is the major pathway? Is threonine ketogenic, glycogenic, or both?
Propionyl CoA
Glycine - major pathway
Pyruvate
Both ketogenic and glycogenic
Besides serine (and THF) and threonine, how can glycine be formed? What 4 things does this require? Why is this special?
From its own parts
CO2, NH4, methylene THF, and pyridoxal phosphate
Only AA that can form from its individual parts
Which pathway of catabolization of serine is least common?
Threonine pathway
Is glycine ketogenic, glycogenic, or both? why?
Glycogenic
because it can revert back to serine which is glycogenic
What is THF derived from? What is its main purpose?
Vitamin folic acid
Serves to transfer 1 carbon units
What are 4 important uses of THF?
Serine, glycine, and histidine
Resynthesize methionine from homocysteine
Synthesis of purines
Formation of methyl group of thymine
What internediate is shared in the synthesis and catabolism of proline, arginine, glutamine, and the catabolism of histidine? Why is its conversion to glutaime important?
Glutamate
Glutmine - non-toxic way of transporting ammonia in the blood
