Amino Acid metabolism
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- Where does the degradation of ingested proteins occur?
- In the gastrointestinal tract?
- Pepsinogen is converted to what, and in what type of fluid (juice)?
- Pepsinogen is converted to active pepsin in gastric juice by the autocatalysis of pepsin itself.
- What types of bonds/proteins does pepsin hydrolyze?
- Pepsin hydrolyzes those peptide bonds of ingested proteins involving the aromatic amino acids (tyrosine, phenylalanine, tryptophan) among others.
- What enzyme converts trysinogen to trypsin? What is the characteristic of the proteins hydrolyzed by trypsin?
- Enteropeptidate converts trypsinogen to trypsin. Free trypsin hydrolyzes those peptide bonds whose carbonyl groups are contributed by lysin and arginine residues in the small intestine.
- How is chymotrypsinogen converted to chymotrypsin? What types of bonds does it hydrolyze?
- Chymotrypsinogen is converted to chymotrypsin by trypsin. It hydrolyzes those peptide bonds involving phenylalanine, tryptophan, and tyrosine.
- Inactive zymogen procarboxypeptidase is converted to ? and removes ?.
- carboxypeptidase; successive carboxyl-terminal residues
- Aminopeptidase hydrolyzes what?
- Amino-terminal residues from short peptides
- What do parietal cells secrete?
- HCl
- What do chief cells secrete?
- Pepsinogen
- What does the gastric mucosa secrete?
- Gastrin. The parietal cells and chief cells of the gastric glands secrete their products in response to the hormone gastrin.
- What is the function of transaminases/aminotransferase?
- They promote the removal of the α-amino groups of most of the L-amino acids. These reactions are called transanimations.
- What reaction does alanine transaminase catalyze?
- The transfer of an amino group to pyruvate.
- What is the function of aspartate transaminase?
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catalyzes an amino group of L-aspartate to oxaloacetate.
It converts L-aspartate to oxaloacetate. - Which six amino acids are degraded to pyruvate?
- serine, glycine, alanine, tryptophan, threonine, cysteine
- Which two amino acids can be directly deaminated and why?
- Serine and threonine can be directly deaminated because each of these amino acids contains a hydroxyl group in its side chain.
- Which enzymes catalyze the direct deamination of serine and threonine?
- Serine dehydratase and threonine dehydratase.
- What does leucine transaminase catalyze?
- An amino group from L-leucine to α-ketoisocaproate.
- What does tyrosine transaminase catalyze?
- Tyrosine transaminase catalyzes an amino group of L-tyrosine to p-hydroxyphenylpyruvate.
- What is threonine deaminated to?
- α-ketobutyrate
- After removal of their amino groups, what is the fate of the carbon skeletons?
- The carbon skeletons of amino acis undergo oxidation to compounds that can enter the citric acid cycle for oxidation to CO2 and H2O.
- Which seven amino acids are degraded to acetyl-CoA
- threonine, isoleucine, leucine, tryptophan, phenylalanine, lysine, tyrosine
- _______ breakdown is the most complex of all the pathways of amino acid catabolism in animal tissues.
- Tryptophan
- Amino acid catabolism to acetyl-CoA leads to ? in humans.
- Succinyl-CoA
- Which five amino acids are converted to α-ketoglutarate?
- proline, glutamate, arginine, glutamine, histidine
- Which four amino acis are converted to succinyl-CoA?
- methionine, isoleucine, valine, threonine
- Which amino acids are degraded by oxygenases? Describe the steps
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Phenylalanine and tyrosine are degraded by oxygenases. The first step is the hydroxylation of phenylalaine to tyrosine via phenylalaine hydroxylase.
Phenylalaline to tyrosine to p-hydroxyphenylpyruvate to homogentisate