Amino Acids

Question 1

Which amino acids form oxaloacetate? And using which enzyme?

Answer 1

Asparagine and aspartate, using aminotransferase (PLP)

Question 2

Which amino acids form alpha-ketoglutarate?

Answer 2

Glutamine, proline, arginine, histidine

Question 3

Glutamine characteristics?

Answer 3

• Is hydrolyzed to glutamate and ammonia by glutaminase

- Glutamate is then converted to A-k by transaminase

Question 4

Proline characteristics?

Answer 4

– Is oxidized to glutamate (same as glutamine)

• Glutamate is then transaminated to A-k

Question 5

Arginine characteristics?

Answer 5

• Is hydrolyzed to arginase to produce ornithine

- Ornithine is then converted to A-k

Question 6

Histidine characteristics?

Answer 6

• Is deaminated to urocanic acid, which then forms FIGLu

Question 7

Which amino acids form pyruvate?

Answer 7

Alanine, Serine, Glycine, Cysteine and Threonine

Question 8

Serine characteristics?

Answer 8

• Converted, reversibly, with glycine

- Serine can be converted to pyruvate

Question 9

Glycine characteristics?

Answer 9

• 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)

Question 10

Alanine characterstics?

Answer 10

• Is converted to pyruvate via transaminase (PLP)

Question 11

How are kidney stones usually formed?

Answer 11

Oxalate, produced from glycine, form precipitates with calcium, which accumulate

Question 12

Which amino acids are involved in the formation of fumarate?

Answer 12

• Phenylalanine is converted to tyrosine by phenylalanine hydroxylase and BH4
• Tyrosine is then converted to fumarate and acetoacetate

Question 13

What are the amino acids that form Acetyl CoA?

Answer 13

Methionine, valine, isoleucine and threonine

Question 14

Methionine characteristics?

Answer 14

• Is the source of SAM and homocysteine

Question 15

S-adenosylmethionine (SAM) formation

Answer 15

Methionine + ATP = SAM

Question 16

Homocysteine characteristics?

Answer 16

• Can form methionine (needs vit B12)
• Can form cysteine (needs vit B6)
• Elevation in homocysteine levels promote vascular disease

Question 17

Isoleucine, leucine and valine characteristics?

Answer 17

Transamination of these 3 to A-k requires vit B6

Question 18

Removal of the carboxyl group of the alpha-keto acids is catalyzed by _____.

Answer 18

Branched-chain alpha-keto acid dehydrogenase (BCKD) of isoleucine, leucine and valine.

Question 19

Maple Syrup Urine disease characteristics

Answer 19

Deficiency in BCKD. Because alpha-keto acids cannot be broken down and they accumulate

Question 20

Serine (and therefore glycine and cysteine) arise from _____.

Answer 20

3-phosphoglycerate

Question 21

The common precursor for proline and arginine is ____.

Answer 21

Ornithine

Question 22

Tyrosine is formed by ____ via which enzyme?

Answer 22

Tyrosine is formed by phenylalanine via PAH

Question 23

How does PKU come about?

Answer 23

Occurs when PAH is deficient; because phenylalanine is not converted into tyrosine, Phe accumulates.

Question 24

Albinism characteristics?

Answer 24

• Defect in tyrosine metabolism -> deficiency of melanin

- Tyrosinase deficiency

Question 25

Menkes syndrome

Answer 25

• Copper deficiency tyrosinase deficiency

- Copper is a required cofactor of tyrosinase

Question 26

What is found in the urine, in alkaptonuria patients?

Answer 26

Homogentisic acid