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BCH4024 > L17: biosynthesis of nonessential & specialized AA's > Flashcards

L17: biosynthesis of nonessential & specialized AA's Flashcards

1
Q

Creatine Kinase rxn

A

Creatine + ATP -> Creatine-P (“ATP buffer” in muscle)

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2
Q

Keq for Creatine kinase rxn?

A

30

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3
Q

Characteristics of Creatinine

A
  • breaks down product of creatine-P in our muscle
  • it is produced at a fairly constant uncatalyzed rate
  • yield depends on muscle mass; higher in men
  • clearance rate tells us how well the kidney is working
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4
Q

3 reactions that form Glutamate

A

Transamination: alpha-KG + AA -> Glutamate + alpha-AA
Reductive amination: alpha-KG + NH3 + NADPH -> glutamate + NADP+
Hydrolysis: glutamine + H2O -> glutamate + NH3

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5
Q

Enzymes for:

  1. transamination
  2. reductive amination
  3. hydrolysis of glutamate
A
  1. transaminase
  2. GDH
  3. glutaminase
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6
Q

the reaction that forms Glutamine

A

glutamate + NH3 + ATP -> glutamine + ADP + Pi

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7
Q

2 reactions that form Aspartate

A

Transamination: OAA + glutamate -> aspartate + alpha-KG
Hydrolysis: asparagine + H2O -> aspartate + NH3

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8
Q

the reaction that forms Asparagine

A

Asp + Gln + ATP -> Asn + AMP + PPi + Glu

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9
Q

the reaction that forms Alanine

A

Pyruvate + Glutamate -> alanine + alpha-KG

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10
Q

What is the Alanine shuttle?

A

it is an inter-organ transfer of ammonia nitrogen. Alanine prevents ammonia toxicity.

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11
Q

What is the key step in proline biosynthesis?

A

the reduction of glutamate to glutamate semi-aldehyde

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12
Q

what can glutamate semi-aldehyde do?

A

it can undergo a side transamination reaction to form ornithine

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13
Q

glutamate is a precursor for ___?

A

it is a precursor for arginine synthesis in the Urea Cycle

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14
Q

hydroxyproline biosynthesis

A

prolyl residue + O=O + alpha-KG -> hydroxyprolyl residue + glutamate

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15
Q

prolyl hydroxylase is ___?

A

it is easily deactivated, forming bound Fe(iii)-O-, which must be reduced by vitamin C to restore enzyme

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16
Q

what does vitamin C deficiency lead to?

A

it leads to unstable collagen (the basis of Scurvy)

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17
Q

what does hydroxyproline stabilize?

A

it stabilizes collagen by forming key hydrogen bonds within the tropocollagen triple helix

18
Q

Serine biosynthesis

A

can from 2 ways from 3-phosphoglycerate

19
Q

Tyrosine biosynthesis

A

Phe + NADPH + O2 -> Tyr + NADP+ + H2O

20
Q

deficiency in phenylalanine hydroxylase?

A

Phenylketonuria (PKU)- high serum Phe and high urinary phenylpyruvate

21
Q

Molecular basis of PKU?

A

rare genetic condition, autosomal recessive, blood Phe rises to 20X above the normal level

22
Q

Elevated Phe __?

A

damages nerve function

23
Q

is PKU a treatable disease?

A

Yes; requires strict “low-phenylalanine” diet, close supervision, becomes a balancing act when a PKU woman is pregnant.

24
Q

Cysteine biosynthesis

A

Methionine is a substrate needed.

Met + ATP -> S-adenosyl-methionine(SAM) -> S-adenosyl-homocysteine -> homocysteine -> cystathionine -> CYSTEINE

25
Q

Specialized AA synthesis: Thyroxin

A

look at slide 85 :)

26
Q

T3 is formed from T4 by ___?

A

peripheral deiodinase

27
Q

T3 binds to __?

A

mobile receptors/transcription factors

28
Q

T3 increases __?

A

basal metabolic rate:

  • increase O2 consumption and the rate of ATP hydrolysis
  • stimulates fat mobilization, raising plasma fatty acids
  • enhances insulin-dependent glucose uptake, gluconeogenesis, and glycogenolysis
29
Q

Which amino acids are neurotransmitters?

A

Glutamate, aspartate, D-Serine, and Glycine

30
Q

what is the main excitatory neurotransmitter?

A

glutamate (serine also excitatory)

31
Q

What are the neurotransmitters that are converted from amino acids?

A
  • gamma-aminobutyric (glutamate)
  • dihydroxy-phenylalanine (phenylalanine)
  • serotonin (tryptophan)
32
Q

how is gamma-aminobutyric acid formed?

A

it is formed by the decarboxylation of L-glutamate in a vitamin B6-dependent reaction

33
Q

how is D-serine formed?

A

it is formed by the racemization of L-serine in a vitamin B6-dependent reaction

34
Q

Heme biosynthesis

A
  • synthesized in a complex series of steps catalyzed by enzymes in mitochondrial and cytosolic compartments
  • the first step occurs in the mitochondrion
35
Q

Heme biosynthesis rxn

A

Succinyl-CoA + Glycine -> alpha-linolenic acid (ALA) + CoA + CO2

36
Q

What does ferrochelatase do?

A

it inserts Fe(ii) into protoporphyrin IX to form HEME

37
Q

Deranged heme production leads to ___?

A

anemia

38
Q

Iron deficiency is ___

A

a leading cause of anemia

39
Q

what replaces Fe2+ in iron deficiency?

A

Sn2+

40
Q

how does Pb2+ produce anemia?

A

by inhibiting heme synthesis; lead has a sweet taste making this s problem for children
- ingested Pb2+ catalyzes DNA strand cleavage

BCH4024 (8 decks)

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