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SMP - MNE Exam 2 > Lecture 36: Amino Acids as Precursors > Flashcards

Lecture 36: Amino Acids as Precursors Flashcards

1
Q

What are the 4 functions of glycine as a precursor?

A
  1. Inhibitory transmitter
  2. Glycocholic acid (bile salt)
  3. Purine synthesis
  4. Heme synthesis
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2
Q

Describe glycine’s function as an inhibitory transmitter.

A

It inhibits impulses traveling down the spinal cord to stimulate skeletal muscle

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3
Q

How does glycine contribute to purine synthesis?

A

It’s directly incorporated into de novo purine synthesis

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4
Q

What are the 2 purines?

A
  1. Adenine

2. Guanine

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5
Q

How does glycine contribute to heme synthesis?

A

Glycine condenses with succinyl-CoA in the first step of heme synthesis and is a building block for porphyrin 9 which coordinates with iron

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6
Q

What are the 2 predominant circulating AAs?

A
  1. Alanine

2. Glutamine

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7
Q

What is the main function of serine?

A

Important source of single carbon fragments (from the R group) => transferred to a folate derivative which can use the C in a variety of ways depending on its oxidative/reductive state (tetrahydrofolates)

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8
Q

What are the 3 functions of glutamine?

A
  1. Amino group and NH4+ transporter
  2. Amino group donor for purine biosynthesis
  3. Amino group donor for amino sugar biosynthesis
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9
Q

Describe the synthesis of amino sugars.

A

Glutamine donates an amino group to F6P which produces glucosamine-6-phosphate => all amino sugars are derived from glucosamine-6-P

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10
Q

What are the 4 functions of glutamate?

A
  1. Excitatory NT
  2. Precursor to GABA
  3. Amino group donor for AA synthesis
  4. Ammonia fixation reactant
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11
Q

Describe the synthesis of GABA.

A

Decarboxylation of alpha carboxyl using PLP as a cofactor = GABA

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12
Q

What does GABA stand for?

A

γ-amino butyrate

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13
Q

What drugs is the GABA receptor a target for?

A

Benzodiazepines and barbiturates

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14
Q

What are the 2 functions of methionine?

A
  1. Methyl group source

2. Polyamine synthesis

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15
Q

How does methionine donate a methyl group?

A

Methionine + ATP => S-adenosyl methionine (SAM)

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16
Q

What is another name for S-adenosyl methionine (SAM)?

A

Ado-met

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17
Q

How does methionine contribute to polyamine synthesis?

A

SAM is decarboxylated using PLP leaving behind propylamine residue attached to sulfur which serves as a precursor for polyamines

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18
Q

What are 2 examples of polyamines? What is their role?

A
  1. Spermine
  2. Spermidine
    + charged and allow for compact packing of DNA/RNA
19
Q

What are the 2 functions of arginine?

A
  1. Urea precursor

2. NO source

20
Q

What is the function of NO?

A

Short-lived second messenger that acts near its synthesis site

21
Q

What 2 cofactors does NO synthesis from arginine require?

A
  1. Flavin

2. Tetrahydrobiopterin

22
Q

What 3 AAs contribute to the synthesis of creatine?

A
  1. Glycine
  2. Arginine
  3. Methionine
23
Q

What is the main function of histidine? Describe the mechanism

A

Histamine precursor via histidine decarboxylation

24
Q

What are the 2 main functions of histamines

A
  1. Stimulates systemic reactions to allergens

2. Stimulates acid release in the stomach

25
Q

What cofactor does the synthesis of histamines from histidine require?

A

PLP

26
Q

What is the main function of phenylalanine?

A

Precursor for tyrosine

27
Q

What are the 10 essential AAs (meaning we cannot make them)?

A

I Want To Kill VHRs. FML

28
Q

Describe the mechanism of tyrosine synthesis using phenylalanine (overall and 2 steps)

A

Coupling of 2 enzymes through the cofactor tetrahydrobiopterin:

  1. Dihydrobiopterin reductase: NADH + 7,8-dihydrobiopterin => NAD+ + 5,6,7,8-tetrahydrobiopterin
  2. Phenylalanine hydroxylase: 5,6,7,8-tetrahydrobiopterin + phenylalanine + O2 => tyrosine + H2O + 7,8-dihydrobiopterin
29
Q

What is phenylketonuria (PKU)? When is this screened for? Treatment?

A

Phenylalanine hydroxylase deficiency: excess phenylalanine impairs neural development

Screened for at birth

Treatment: inhibit intake of phenylalanine and take tyrosine supplements

30
Q

What is a deficiency in the enzyme dihydrobioterin reductase? Consequences?

A

Inability to regenerate the cofactor biopterin, which is used in many reactions: very serious consequences

31
Q

What are the 3 functions of tyrosine?

A
  1. Catecholamine synthesis
  2. Thyroid hormone precursor
  3. Melanin precursor
32
Q

Describe the catecholamine synthesis pathway.

A

Tyrosine → Dopa (decarboxylation) → Dopamine → Norepi → Epi

33
Q

What cofactor is needed for the conversion of tyrosine to dopa?

A

Biopterin

34
Q

How is melanin synthesized?

A

Tyrosinase: dopa oxidation

35
Q

What is albinism caused by?

A

Tyrosinase deficiency

36
Q

What are the 3 functions of tryptophan?

A
  1. Serotonin precursor
  2. Nicotinic acid precursor
  3. Indoleacetate precusor
37
Q

How is serotonin synthesized? Cofactors used?

A

Hydroxylation of tryptophan at C5 using biopterin + decarboxylation using PLP

38
Q

List the 7 reactions that require PLP as a cofactor? What reactions are these?

A
  1. Glutamate → GABA
  2. α-ketoglutarate + amino acid → glutamate + -keto acid (transamination)
  3. SAM → precursor of polyamines
  4. Ornithine → putrescine
  5. Histidine → histamine
  6. Dopa → dopamine
  7. Tryptophan → serotonin

All decarboxylations except for #2: transamination

39
Q

List the 3 reactions that require Tetrahydrobiopterin as a cofactor? What reactions are these?

A
  1. Arginine → NO
  2. Phenylalanine → tyrosine
  3. Tryptophan → serotonin

All hydroxylations

40
Q

Describe the synthesis of nicotinic acid. What is it used for? Enough to eliminate dietary need?

A

Tryptophan degradation => nicotinic acid: NAD+ precursor

NOPE, not enough

41
Q

Write out the reaction of ammonia fixation using glutamate.

A

Glutamate + NH4+ + ATP => glutamine + ADP + Pi + H+

42
Q

What cells produce NO?

A
  1. Macrophages
  2. Vascular endothelial cells
  3. Neurons
  4. Hepatocytes
43
Q

Function of Indoleacetate?

A

Plant growth factor to do geotropism and phototropism

SMP - MNE Exam 2 (17 decks)

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