Lecture 36: Amino Acids as Precursors Flashcards Preview

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

Flashcards in Lecture 36: Amino Acids as Precursors Deck (43)
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1

What are the 4 functions of glycine as a precursor?

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

2

Describe glycine's function as an inhibitory transmitter.

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

3

How does glycine contribute to purine synthesis?

It's directly incorporated into de novo purine synthesis

4

What are the 2 purines?

1. Adenine
2. Guanine

5

How does glycine contribute to heme synthesis?

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

6

What are the 2 predominant circulating AAs?

1. Alanine
2. Glutamine

7

What is the main function of serine?

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)

8

What are the 3 functions of glutamine?

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

9

Describe the synthesis of amino sugars.

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

10

What are the 4 functions of glutamate?

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

11

Describe the synthesis of GABA.

Decarboxylation of alpha carboxyl using PLP as a cofactor = GABA

12

What does GABA stand for?

γ-amino butyrate

13

What drugs is the GABA receptor a target for?

Benzodiazepines and barbiturates

14

What are the 2 functions of methionine?

1. Methyl group source
2. Polyamine synthesis

15

How does methionine donate a methyl group?

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

16

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

Ado-met

17

How does methionine contribute to polyamine synthesis?

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

18

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

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

19

What are the 2 functions of arginine?

1. Urea precursor
2. NO source

20

What is the function of NO?

Short-lived second messenger that acts near its synthesis site

21

What 2 cofactors does NO synthesis from arginine require?

1. Flavin
2. Tetrahydrobiopterin

22

What 3 AAs contribute to the synthesis of creatine?

1. Glycine
2. Arginine
3. Methionine

23

What is the main function of histidine? Describe the mechanism

Histamine precursor via histidine decarboxylation

24

What are the 2 main functions of histamines

1. Stimulates systemic reactions to allergens
2. Stimulates acid release in the stomach

25

What cofactor does the synthesis of histamines from histidine require?

PLP

26

What is the main function of phenylalanine?

Precursor for tyrosine

27

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

I Want To Kill VHRs. FML

28

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

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

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

Phenylalanine hydroxylase deficiency: excess phenylalanine impairs neural development

Screened for at birth

Treatment: inhibit intake of phenylalanine and take tyrosine supplements

30

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

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