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Metabolism > Amino Acids as precursors > Flashcards

Amino Acids as precursors Flashcards

1
Q

what are AA used for

A

gluconeogenesis, protein building blocks

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2
Q

what is the AA that serves directly as a neurotransmitter?

explain

A

glycine

Functions directly as a neurotransmitter- acts to block impulses traveling in the spinal cord to stimulate skeletal muscle

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3
Q

Glycine is also a precursor for what

A

clycocholic acid (bile salt)

It is conjugated to cholesterol derivative to form glycocholic acid (bile salt)

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4
Q

biochemist’s simple definiton of neurotransmitter ( 4 things)

A

Molecule that is synthesized and stored in synaptic vesicles in neural cells

Release is triggered by an action potential

Bound & recognized by target cell

Activity can be regulated

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5
Q

which nucleic base is synthesized de novo using glycine

A

purines

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6
Q

what does glycine condenses with in the first step of heme biosynthesis

what is end product?

A

succinyl CoA

(protoporphyrin IX + Iron) to make heme

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7
Q

what are the 2 predominant circulation AA’s

A

Along with glutamine, a predominant circulating amino acid

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8
Q

what does Alanine do?

what reaction is involved?

what is the name of the relevant cycle?

A

Transports amino groups from muscle to liver (transamination from muscle pyruvate) in a process called the glucose-alanine cycle

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9
Q

what is Serine used for?

A

Source of one-carbon fragments (folate derivatives) used in biosynthesis

one carbon fragments with folate is used are 1 C building blocks

many steps require addition of 1 carbon units

tetrahydrofolate is vitamin cofactor

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10
Q

describe glucose alanine cycle

A

glucose broken down to pyruvate

reacted with glutamate via alanine aminotransferase to make alpha-ketogluterate and alanine

carried in blood to liver

alanine reacts with alpha ketogluterate to remake glutamate and pyruvate using same enzyme ( alanine aminotransferase)

pyruvate used to regenerate glucose through gluconeogenesis

Glutamate releases NH4+ in liver with goes through urea cycle and is excreted as urea

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11
Q

glutamine is used for what

A

serves as amino transporter like alanine

source of NH4+ in kidney

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12
Q

what else is glutamine involved in

A

Amino group donor in purine biosynthesis

Amino group donor in biosynthesis of amino sugars

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13
Q

what is the key rxn of amino sugar synthesis

A

Fructose-6-P + glutamine —>
Glucosamine-6-P + glutamate

-all amino sugars are then derived from Glucosamine-6-P

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14
Q

glutamate is used for what

A
  • primary Neurotransmitter in CNS (flavor enhancer)
  • acts on both ion channels and G coupled receptors
  • in food as MSG
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15
Q

where are aminosugars found?

A

extracellular matrix and certain connective tissues

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16
Q

how is glutamate made into GABA? name enzyme and cofactor used

what is GABA receptor a target for?

A

glutamate a source of gamma amino butyrate (GABA) via decarboxylation of the alpha-carboxyl.
Enzyme: glutamate decarboxylase and PLPcofactor

GABA is the major inhibitory transmitter in the brain;

  • the GABA receptor is the target of benzodiazepines/ barbiturates
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17
Q

glutamate also participates in what reaction involving amino groups

A

-transaminations: glutamate is the source of amino groups for most other amino acids

-donates n terminus amine group to form alpha ketogluterate ; converting alpha keto acid to L-amino acid (generic)
Enzyme: aminotransferase

  • Pyridoxal phosphate (PLP) is cofactor
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18
Q

PLP is cofactor in what types of reactions

A

decarboxylations and transaminations

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19
Q

gluatamate is converted to glutamine via what

A
  • ammonia fixation

- glutamate + NH4 + + ATP –> glutamine + ADP + Pi + H+

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20
Q

minor pathway that makes glutamate and fixates ammonium ion

A

NH4 + alpha-ketogluterate –> glutamate + H2O

enzyme: glutamate dehydrogenase

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21
Q

methionine reacts with ATP to form what

A

S-adenosyl methionine (SAM)- source of methyl groups for most methylation reactions

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22
Q

SAM can be decarboxylated to leave

what cofactor used?

A

a propylamine residue attached to the sulfur - precursor of spermine and spermidine (“polyamines”)

PLP used

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23
Q

decarboxylated adoMet reacts with what enzymes

what is made ultimately

A

either propylaminotransferase I: or II to make polyamines

  • polyamines are made: spermidine and spermine
24
Q

what charge do polyamines have?

what does this help with

A
  • positively charge amine groups

- helps with binding of nucleic acids

25
Q

how is putrecine made?

A

decarboxylation of ornithine

26
Q

what is putricine reacted with? via what enzyme?

what products does it make?

A

it is reacted with decarboxylated adoMet via enzyme propylaminotransferase I

makes spermidine and methylthioadenosine

27
Q

spermine is made by what?

producing what

A

reacting spermidine with adoMet via enzyme propylaminotransferase II

producing [CH3–S–Adenosine] along with spermine

28
Q

arginine: what two uses

A
  • immediate precursor of urea via arginase in urea cycle

- Source of NO, a second messenger

29
Q

how many steps to make NO from arginine

what is enzyme

what cofactors required?

A

2 steps

nitric oxide synthase

flavin and tetrahydrobiopterin

30
Q

how does NO work?

A

activates guanylyl cyclase production of cGMP in target cells… cascade

31
Q

what is NO given as medicine for?

A

sickle cell anemia to prevent log jams

32
Q

creatine is made from what

A

arginine, glycine and methyl group from adoMet (methionine)

33
Q

phosphocreatine is

A

an energy reserve AKA energy component buffering systems

34
Q

histamine is made from what

A

histidine (decarboxylated by histidine decarboxylase with PLP to make it

35
Q

histamine is used for

A

a major stimulant of acid release in the stomach and in systemic reactions to allergens

36
Q

in normal conditions, which ringed AA is dietary essential AA

A

phenylalanine

37
Q

What is tyrosine made from

A

phenylalanine

38
Q

what cofactor is needed for tyrosine synthesis

A

tetrahydrobiopterin which is regenerated by NADH via enzyme dihydrobiopterin

39
Q

phenylalanine converted to tyrosine by what enzyme

A

phenylalanine hydroxylase

40
Q

what does biopterin cofactor provide for tyrosine synthesis

A

the electrons for reduction of oxygen in hydroxylation of phenylalanine- regeneration requires specific reductase

41
Q

what is PKU?

how is it controlled via diet?

how is it screened?

A

Deficiency of phenylalanine hydroxylase (phenylketonuria, PKU) is usually screened for at birth (blood sample to measure elevated phenylalanine levels) - controllable by specialized diet with limited phe, and tyr supplementation - less required by puberty

42
Q

Deficiency of the biopterin reductase is more severe. why?

A
  • is more severe and cannot be controlled by dietary means

- reason is because tetrahydrobiopterin is needed in other pathways so more severe impact

43
Q

what causes disease state of PKu

A

excess phenylalanine causes developmental problems

that is why diet is less critical after puberty

44
Q

what is tyrosine a precursor of

A

Tyrosine is a precursor of several important molecules: dopa (dihydroxyphenylalanine), dopamine, epinephrine/norepinephrine

also precursor of thyroxine/T3

In addition, melanin is derived by oxidation of dopa catalyzed by tyrosinase (lack of this e nzyme results in classic albinism)

45
Q

order in which catecholamines are made

A

tyrosine to Dopa to Dopamine to Norepinephrine to Epinephrine

46
Q

dopamine clinical correlate

A

Parkinsons

47
Q

how is dopamine made

A

by decarboxylation of dopa

48
Q

what are Norepi and epi

A

Both epinephrine and norepinephrine are neurotransmitters and signaling molecules (fight or flight response - sympathetic nerves)

49
Q

What is T3 called and how is it made?

what is T4 called and how is it made?

A

Active form is tri-iodothyronine (T3; T4 is thyroxine). This is formed by iodination and condensation of tyrosine residues in thyroglobulin followed by proteolysis of the protein and hormone release

50
Q

what kind of tyrosine is in T3 and T4?

A

iodinated tyrosine

51
Q

tyrosines in what molecule are iodinated for T3 and T4 production?

A

thryoglobulin

52
Q

what is tryptophan used for what neurotransmitter?

what 2 types of rxns yield this?

what are the cofactors mentioned?

A

serotonin production

Hydroxylation (5-position) followed by decarboxylation yields serotonin, a multi-faceted neurotransmitter.

The hydroxylation step requires Biopterin cofactor; decarboxylation step requires PLP cofactor.

53
Q

what else is made from Trp? can this be sufficient source of this molecule?

A

Some tryptophan can be degraded to nicotinic acid (precursor for NAD+) but this usually is insufficient to eliminate dietary need.

54
Q

what is the 3rd thing that can be made from trp

A

Indolacetate: plant growth factor

55
Q

decarboxylation and transamination cofactor

A

PLP

56
Q

biopterin is used in what rxns

A

hydroxylation

Metabolism (8 decks)

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