Amino Acids Flashcards
Which amino acids form oxaloacetate? And using which enzyme?
Asparagine and aspartate, using aminotransferase (PLP)
Which amino acids form alpha-ketoglutarate?
Glutamine, proline, arginine, histidine
Glutamine characteristics?
- Is hydrolyzed to glutamate and ammonia by glutaminase
- Glutamate is then converted to A-k by transaminase
Proline characteristics?
– Is oxidized to glutamate (same as glutamine)
- Glutamate is then transaminated to A-k
Arginine characteristics?
- Is hydrolyzed to arginase to produce ornithine
- Ornithine is then converted to A-k
Histidine characteristics?
- Is deaminated to urocanic acid, which then forms FIGLu
Which amino acids form pyruvate?
Alanine, Serine, Glycine, Cysteine and Threonine
Serine characteristics?
- Converted, reversibly, with glycine
- Serine can be converted to pyruvate
Glycine characteristics?
- Glycine is converted to serine, which is then converted to pyruvate
- Glycine can be converted to glyoxylate by transaminase; if the transaminase is deficient, oxaluria results (renal failure due to oxalate accumulation)
Alanine characterstics?
- Is converted to pyruvate via transaminase (PLP)
How are kidney stones usually formed?
Oxalate, produced from glycine, form precipitates with calcium, which accumulate
Which amino acids are involved in the formation of fumarate?
- Phenylalanine is converted to tyrosine by phenylalanine hydroxylase and BH4
- Tyrosine is then converted to fumarate and acetoacetate
What are the amino acids that form Acetyl CoA?
Methionine, valine, isoleucine and threonine
Methionine characteristics?
- Is the source of SAM and homocysteine
S-adenosylmethionine (SAM) formation
Methionine + ATP = SAM
Homocysteine characteristics?
- Can form methionine (needs vit B12)
- Can form cysteine (needs vit B6)
- Elevation in homocysteine levels promote vascular disease
Isoleucine, leucine and valine characteristics?
Transamination of these 3 to A-k requires vit B6
Removal of the carboxyl group of the alpha-keto acids is catalyzed by _____.
Branched-chain alpha-keto acid dehydrogenase (BCKD) of isoleucine, leucine and valine.
Maple Syrup Urine disease characteristics
Deficiency in BCKD. Because alpha-keto acids cannot be broken down and they accumulate
Serine (and therefore glycine and cysteine) arise from _____.
3-phosphoglycerate
The common precursor for proline and arginine is ____.
Ornithine
Tyrosine is formed by ____ via which enzyme?
Tyrosine is formed by phenylalanine via PAH
How does PKU come about?
Occurs when PAH is deficient; because phenylalanine is not converted into tyrosine, Phe accumulates.
Albinism characteristics?
- Defect in tyrosine metabolism -> deficiency of melanin
- Tyrosinase deficiency
Menkes syndrome
- Copper deficiency tyrosinase deficiency
- Copper is a required cofactor of tyrosinase
What is found in the urine, in alkaptonuria patients?
Homogentisic acid
