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Endocrine Biochem > Amino Acid Synthesis & Degradation > Flashcards

Amino Acid Synthesis & Degradation Flashcards

1
Q

describe the contributors to, and the uses of, amino acids in your body’s amino acid pool

A

Contributors: dietary protein and endogenous protein

Uses of: purine and pyrimidine synthesis, nucleotides, heme, hormones, urinary metabolites and other nitrogenous products

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2
Q

non-essential amino acids from glucose

A

GAS CAAP

Glycine
Alanine
Serine

Cysteine
Arginine
Asparagine
Proline

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3
Q

non-essential amino acid from essential amino acid

A

tyrosine (carbons come from phenylalanine

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4
Q

is arginine essential or non-essential? explain.

A

nonessential most of the time (fully grown, not pregnant, no wounds). it can be made by the urea cycle. During childhood, pregnancy, and wound healing, however, it is essential

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5
Q

essential amino acids

A

PVT TIM HALL

phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, histidine, arginine, leucine, lysine

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6
Q

what cells are good at amino acid synthesis and degredation?

A

liver cells! (except for bcaa)

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7
Q

describe the synthesis of serine from glucose. draw the structures of 3-phosphoglycerate and serinne. predice the processes and the types of enzymes required to convert 3-phosphoglycerate into serine

A
  1. glucose gets converted to 3-phosphoglycerate in glycolysis.
  2. 3-phosphoglycerate undergoes oxidation (via a dehydrogenase, changing alpha hydroxy to alpha keto)
  3. transamination (changing alpha keto to alpha amino) (PLP needed as cofactor)
  4. hydrolysis
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8
Q

describe your body’s synthesis of glycine from serine. give the rxn catalyzed by serine hydroxymethyltransferase

Name cofactor

A

in the synthesis of glycine, serine has to lose its side chain.

in the serine hydroxymethyltransferase rxn, tetrahydrofolate derivative get produced. PLP is cofactor. serine -> glycine transformation occurs

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9
Q

describe your body’s catabolism of methionine and synthesis of cysteine from serine and methionine

A

In cysteine synthesis, the sulfur comes from methionine and the rest comes from serine.

in methionine degradation, methionine becomes homocysteine via the methylation cycle:

  1. methionine turns into SAM
  2. SAM gives away a methyl group becoming S-adenosyl homocysteine
  3. adenosyl group is lost back to homocysteine
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10
Q

describe the rxn catalyzed by cystathionine beta-synthase and the cofactor require residing in the enzyme’s active site

A

homocysteine + serine ——–> cystathionine
enzyme: cystathionine beta-synthase
PLP = catalytic cofactor

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11
Q

describe the rxn catalyzed by cystathionase and the cofactor require residing in the enzyme’s active site

A

cystathionine (gets broken apart into…) —–> cysteine + alpha-ketobutyrate
enzyme: cystathionase

  • loss of N which comes off as NH4+

PLP = catalytic cofactor

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12
Q

Describe the sources of propionyl CoA, and the sequence of rxns that converts propionyl CoA into succinyl CoA

A

sources of propionyl CoA:

  1. (VITM): valine, isoleucine, threonine, methionine
  2. beta-oxidation of odd chain fatty acids where the last 3 carbons become propionyl groups of prop CoA
  3. when cholesterol is turned into an unconjugated bile sale
  4. propionic acid made in the colon when colonic bacteria acts upon fiber
rxns:
propionyl CoA + ATP  ------> methylmalonyl CoA + ADP + Pi
enzyme: propionyl CoA carboxylase
catalytic cofactor = biotin
source of new carboxyl group? CO2

methylmalonyl CoA ——> succinyl Coa
enzyme: methylmalonyl CoA
catalytic cofactor = vitamin B12

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13
Q

describe your body’s synthesis of alanine from glucose

A
  1. glycolysis (glucose –> pyurvate)
  2. transaminase rxn (ALT)

ALT rxn:
alanine + alpha-KG —–> pyruvate + glutamate
enzyme: alanine transaminase (ALT)

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14
Q

describe your body’s synthesis of aspartate & asparagine from glucose

A
  1. glucose –> pyruvate (glycolysis)
  2. pyruvate –> OAA (pyruvate carboxylase)
  3. OAA + glutamate <–> aspartate + alpha-KG (AST) *gains N from NH4+
  4. glutamate –> glutamine (glutamine synthetase) *gains N from ammonium ion
    or
  5. aspartate –> asparagine (asparagine synthetase) *gains N from glutamine’s side chain
    - breaks AMP + PPi, costs cell a 2nd ATP to turn AMP into ADP (adenylate cyclase rxn)
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15
Q

Describe your body’s synthesis of glutamate from glucose

A
  1. glucose –> pyruvate (glycolysis)
  2. some pyruvates –> acetyl CoA (pyruvate dehydrogenase) in mito mtrix
    or
  3. some pyruvates –> OAA (pyruvate carboxylase rxn) in cytosol
  4. OAA & acetyl CoA can be turned –> citrate (citrate synthase rxn) in mito matrix
  5. citrate –> isocitrate –> alpha-KG (TCA cycle)

then, there are 2 ways to turn alpha-KG into glutamate

  1. transamination rxn
  2. glutamate dehydrogenase rxn (using an NH4+)

glutamate –> glutamine (glutamate synthase rxn which uses another NH4+ and ATP)

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16
Q

list three other amino acids that can be made from glutamate

A

glutamate can be turned into proline and arginine

glutamate –> glutamate semialdehyde –> proline and arginine

reduces glutamate’s side chain from a carboxylic acid to aldehyde

glutamate semialdehyde can become ornithine –> arginine (urea cycle)

17
Q

list the aromatic amino acids. describe your body’s synthesis of tyrosine from phenylalanine

describe the role of tetrahydrobiopterin (BH4) in hydroxylations of aromatic amino acids and give the precursor for your body’s synthesis of BH4

A

phenylalanine, tryptophan, tyrosine

tyrosine synthesis:
1. hydroxylation rxn of phenylalanine
phenylalanine + O2+ BH4 —–> tyrosine + BH2
first reducing agent: phenylalanine
oxidizing agent: O2
second reducing agent: BH4 (in all hydroxylation of aromatic amino acid rxns)

The BH2 gets recycled in the dihydrobiopterin reductase rxn
reducing agent: NADH + H+

18
Q

what is PKU disease? effects?

what sweetner is a source of phenylalanine?

describe the biochemical cause of classical phenylketonuria (PKU disease).

describe the biochemical cause of non-classical PKU disease

A

phenylketonuria happens when a person has difficulty turning phenylalanine into tyrosine, causing phenylketones (degradation products of phenylalanine) to build up. This can cause severe mental retardation

rigorous testing is done at birth for PKU disease and a person can be put on a special diet that has enough phe to meet the body’s needs

aspartame/nutrasweet is a source of phe

classical PKU disease: change in genetic code for phenylalanine hydroxylase (only affects the breakdown of phe –> tyr

non-classical PKU disease: changing in coding for dihydrobiopterin reductase, which affects a person’s ability to hydroxylate any aromatic amino acid. EVEN MORE DANGEROUS

19
Q

list the six entry points into mainstream metabolism when the carbon skeletons of amino acids are catabolized

A 
outside of the TCA cycle
- pyruvate 
- acetyl CoA
intermediates of TCA cycle
- alpha-KG
- succinyl CoA (VITM can become propionyl CoA --> succinyl CoA)
- fumarate
- OAA
20
Q

list the branch chain amino acids

which can become propionyl CoAs?

describe how the catabolism of bcaa begins. why doesn’t the liver catabolize bcaa significantly

A

valine, leucine, isoleucine

valine and leucine can become propionyl CoAs

  1. branched chain amino acid transaminase
    - alpha-keto acid: alpha-KG which gets turned to glutamate
    - catalytic cofactor: PLP
    - turns bcaa’s into bcka’s
  2. branched chain keto-acid dehydrogenase (bckadh)
    - bcka gets dehydrogenated and attached to CoA
    - THREE catalytic cofactors: thyamine pyrophosphate, lipoic acid, FAD (flavin adenine dinucleotide)
  3. decarboxylation & oxidation of alpha-keto acid
    products: CO2 and NADH
  4. attachment to CoA
  5. more oxidation (e- sent to ETC for oxidative phosphorylation regeneration of ATP)
21
Q

describe the similarities between BCKADH, PDH, and alpha-KGDH

A

branched chain keto-acid dehydrogenase
pyruvate dehydronase
alpha-ketoglutarate dehydrogenase

similarities:

  • an alpha-keto acid gets dehydrogenated and attached to a CoA
  • THREE catalytic cofactors needed:
    1. thyamine pyrophosphate
    2. lipoic acid
    3. flavin adenine dinucleotide (FAD)
22
Q

the vitamin part of NADH

A

nicotinamide (from vitamin B3)

23
Q

what three enzymes require lipoic acid as a cofactor?

what four enzymes require thiamine, in the form of thiamine pyrophosphate (TPP), as a cofactor?

A

lipoic acid:
pyruvate dehydrogenase
alpha-KG dehydrogenase
bcka dehydrogenase

TPP:
pyruvate dehydrogenase
alpha-KG dehydrogenase
bcka dehydrogenase
transketolase (from the PPP; main lab test for thiamine deficiency is to test how well this rxn works in a person's RBCs)
24
Q

name the amino acid precursor(s) that your body uses to make carnitine

A

lysine + methionine (in form of SAM)

25
Q

name the amino acid precursor(s) that your body uses to make glutathione

give the rxns catalyzed by glutathione peroxidase and glutathione reductase

A

glutamate, cysteine, glycine

glutathione peroxidase rxn
GSH + HSG + H2O2 –> GSSG (glutathione disulfide) + 2 H2O
selenoprotein: has selenocysteine in its building blocks

glutathione reductase rxn
GSSG + NADPH + H+ –> 2 GSH + NADP+

26
Q

name the amino acid precursors for conjugation of bile salts

A

taurine and glycine

taurine’s acid part is a sulfonic acid part rather than a carboxylic acid part; it comes from cysteine

27
Q

name the amino acid precursors for nicotinamide adenine dinucleotide (NAD+ etc)

A

tryptophan, when not being built from vitamin B3 nicatinomide

28
Q

name the amino acid precursors for thyroid hormones

A

tyrosine

T4 = tetraioddothyronine
T3 = tri-iodothyronine
29
Q

name the amino acid precursors for heme

also say which TCA cycle intermediate is required

A

glycine

intermediate needed: succinyl CoA

30
Q

name the amino acid precursors for creatine

also give the reversible rxn catalyzed by creatine kinase

A

glycine & arginine (Ns come from here)
methyl group comes from methionine in the form of SAM

creatine phosphate + ADP <——-> creatine + ATP

from ATP –> ADP is muscle contraction
from ADP –> ATP is oxidation of fuel
from ADP –> ATP is from creatine phosphate to creatine

31
Q

name the amino acid precursors for catecholamines (dopamine, norepinephrine, and epinephrine)

A

methionine in the form of SAM

32
Q

name the amino acid precursors for melanin

A

tyrosine

33
Q

name the amino acid precursors for serotonin (5-HT)

A

tryptophan

34
Q

name the amino acid precursors for melatonine

A

tryptophan

35
Q

name the amino acid precursors for histamine

A

histadine

36
Q

name the amino acid precursors for gamma amino butyric acid (GABA)

A

glutamate

37
Q

name the amino acid precursors for nitric oxide

A

arginine

38
Q

name the amino acid precursors for purine nucleotides

A

glutamate, glycine, aspartate

39
Q

name the amino acid precursors for pyrimidine nucleotides

A

glutamate, aspartate

Endocrine Biochem (7 decks)

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