Lect 8 Protein & AA Metabolism Flashcards Preview

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Flashcards in Lect 8 Protein & AA Metabolism Deck (27):
1

Amino Acid Pool is population of free AAs that is supplied by _ ? Depleted by _ ?

  • Protein Turnover, Digested Food (essential AAs) , and De Novo Synthesis (nonessential AAs)
  • Production of protein, Nitrogen containing compound synthesis, Degradation

2

Proteolysis is _ 

Degradation of proteins for reabsorption

3

Exopeptidase

attacks C- (carboxypeptidase) or N-terminus (aminopeptidase) ends

4

Endopeptidase

attacks within protein at specific site (digests internal peptide bonds)

5

What pH are proteases active in Lysosomal Degradation/Autophagy? Inactive?

Proteases active at acidic pH of lysosome (5), inactive at pH of cytoplasm (7)

6

How does intracellular proteolytic control work?

Proteolytic enzymes controlled through "marking" mechanisms tagging protein substrate for degradation

7

How does proteasomal degradation work?

Large proteasome cytoplasmic complexes cleave polyubiquinated proteins

8

What is the Extracellular Proteolytic Control mechanism?

Proteolytic enzymes secreted as needed (inactive zymogens activated by proteolytic cleavage)

9

Essential AA

PVT TIM HALL

  • Phenylalanine (Phe)
  • Valine (Val)
  • Threonine (Thr)
  • Tryptophan (Trp)
  • Isoleucine (Ile)
  • Methionine (Met)
  • Histidine (His)
  • Arginine (Arg)
  • Leucine (Leu)
  • Lysine (Lys)
  • Glutamine (Gln)

10

Nonessential AA

  • Alanine (Ala)
  • Aspartate (Asp)
  • Asparagine (Asn)
  • Cysteine (Cys)
  • Glutamate (Glu)
  • Gultamine (Gln)
  • Glycine (Gly)
  • Proline (Pro)
  • Serine (Ser)
  • Tyrosine (Tyr)

11

Ketongenic AAs

2

Leucine and Lysine

Acetyl CoA or Acetoacetate --> Precursor for FA/Ketone Synthesis

12

Ketogenic/Glucogenic AAs

5

Isoleucine

Tryptophan

Phenylalanine

Tyrosine

Threonine

13

Glucogenic AAs

13

Valine

Histidine, Arginine, Asparagine, Glutamine

Methionine, Alanine, Aspartate,  Glutamate, Glycine, Proline, Serine, Cysteine

Pyruvate/TCA Cycle Intermediates --> Gluconeogenesis Precursor

14

Consequences of Hyperhomocysteinemia and Homocystinuria

Deficiency in Met Metabolism

  • Defective metabolism in homocysteine
    • Vit B6, B12, folic acid deficiencies or inherited defects in enzymes (cystathionine B-synthase)
  • Risk factor in atherosclerotic heart disease and stroke

15

Maple Syrup Urine Disease

Deficiency in BCA Metabolism (Val, Ile, Leu)

Deficient BCA a-ketoacid dehydrogenase complex (BCKD)

BCAs in urine

Higher in Mennonite, Amish, Jewish Populations

BCAs not degraded in Liver (no aminotransferase)

16

Phenylketonuria

Deficiency of Phe Metabolism 

Phe is converted to _ by _

What is secondary PKU?

Defects in Phenyalanine Hydroxylase (PAH) 

Converted to Tyrsonine via Phenylalinine Hydroxylase

Converted to phenylpyruvate and then to phenyllactate and phenylacetetate (Disrupts neurotransmission)

Tetrahydrobiopterin (BH4) deficiency (cofactor of PAH)

17

What are Transaminase Reactions?

What coenzyme do they require?

What is the clinical relevance of these enzymes?

Amino group transferred to a-ketoacid (coupled reactions)

Transaminases/Aminotransferases

Require PLP (Vit B6 derivative)

Clinical Relevance: ALT and AST biomarker for liver function

18

Tyrosine Derivatives

Tyr - Dopa --> Dopamine (Parkinsonism) --> Norepi --> Epi

Tyr --> Thyroid Hormones T3/T4 (Grave's, Hyper/Hypothyroidism)

Tyr --> Melanin (Albinism)

19

Tryptophan Derivatives

Trp --> 5 -Hydroxytryptophan --> Serotonin --> Melatonin

Trp --> Niacin (Needs Vit B6) --> NAD+/NADP+

20

What is Thyroglobulin and how does it impact Thyroid Hormones?

How is hyperthyroidism treated?

Thyroglobulin made by thyroid and produces T4 and T3

Hyperthyroidism treated with agents which block iodination of thryroglobulin to decrease T4 and T3

21

Albinism and Tyrosinase

Albinism is due to severe lack of melanin (tyrosine --> melanin blocked due to tyrosinase defect)

Partial/Complete absence of pigmentation in skin, hair, and eyes

22

How does Parkinsonism develop?

Loss of conversion of Dopa to NT Dopamine in brain due to destruction of neural tissue.

L-Dopa treatment (dopamine can't cross BBB)

23

How is ammonia removed in the brain and in muscle?

Brain: a-KG --> Glu --> Gln (glutamine synthase) w/ NH3 --> NH4+ to Urea Cycle

Muscle: Ala + a-KG --> Glu (ALT) --> NH4+ to Urea Cycle

24

Describe the Urea Cycle

NH4+ --> Carbamoyl Phosphate (Carbamoyl phosphate Synthetase (rate limiting step) 

Carbamoyl Phosphate + Ornothine --> Citrulline

Citrulline converted up to Arginine (arginase removes ammonia and forms Urea)

Sent to Kidneys in the blood for excretion

25

Why is Ammonia Toxic?

What condition can it cause?

Toxic effects on brain and CNS since NH3 has ability to permeate membranes and causes pH imbalance

Mitochondrial dysfunction

26

How does diet affect the Urea Cycle?

Urea production increased in high protein diet, decreased in high CHO diet

27

Creatine is what 3 AAs?

Methionine, Arginine, and Glycine