Protein/AA Metabolism Flashcards Preview

MCM - Rusheil > Protein/AA Metabolism > Flashcards

Flashcards in Protein/AA Metabolism Deck (31):
1

Exopeptidase

Attacks C- termini and N- termini of polypeptides/proteins.

(Carboxypeptidase and aminopeptidase, respectively)

2

Endopeptidase

Attacks within the protein at specific site (digests internal peptide bonds)

3

Lysosomes in proteolytic control

Intracellular proteolytic control - low pH in lysozyme and contain many proteolytic enzymes

Non-selective protein degradation:
-macroautophagy (many proteins in an endosome taken up)
-microautophagy (one protein take up at a time)
-chaperone-mediated autophagy (CMA)

4

Proteosome structure

19S regulatory (capping) units on either side of a 20S catalytic core unit that degrades the ubiquitinylated protein

5

Zymogen example

Inactive: Trypsinogen and chymotrypsin released into SI lumen

Active: Trypsinogen activated by enzyme enterokinase
-Active Trypsin activates chymotrypsinogen

6

Ketogenic amino acids

Leucine and Lysine (the L’s)

7

Ketogenic AND Glucogenic AAs

Phe, Ile, Thr, Tyr, Trp

Mnemonic: brad PITTT

8

Ketogenic AAs

Can act as precursors for alpha keto acids, ketone bodies and fatty acids

9

Glucogenic AAs

Can act as precursors for glucose synthesis via gluconeogenesis

10

Transamination

Shuffling of amine groups

Amino group transferred to alpha-ketoacid

Enzymes called: transaminase/aminotrasnferases - Requires PLP from Vitamin B6 (Pyridoxyl)

11

ALT

Alanine Aminotransferase

Pyruvate + GLUTAMATE ALANINE + alpha-ketoglutarate

12

AST

Aspartate Aminotransferase

Oxaloacetate + GLUTAMATE ASPARTATE + a-ketoglutarate

13

Succinyl-CoA amino acid precursors

Met, Val, Ile

14

Homocystinuria / Hyperhomocystemia

In the metabolism of Methionine, and intermediate homocysteine is formed.

Cystathionine synthase metabolizes homocysteine further with PLP.
-When enzyme is defective OR vitamin deficiency (B6, B12, folic acid), homocysteine builds up
-homocysteine dimerizes with itself to form homocystine = TOXIC

Homocystine accumulation = homocystinuria / hyperhomocystemia

15

Homocystinuria affected organs

Eye
Skeletal
CNS
Vascular

16

Branched Amino Acids

Ile, Leu, Val

17

Maple Syrup Urine Disase (MSUD)

Autosomal disease resulting from branched-chain alph-keto acid dehydrogenase complex (BCKD) deficiency.
—-> Branched-chain ketoaciduria

-branched-chain AAs present in urine = maple syrup odor
-branched-chain AA accumulate in blood = toxic effect —> mental retardation

Treatment: synthetic diet limiting Val, Ile, Leu

18

Phenylketonuria (PKU)

PKU caused by defects in Phenylalanine Hydroxylase. Disrupts metabolism of Phe.

Or caused by tetrahydrobiopterin deficiency

Build-up of Phe forms Phenyllactate and Phenylacetate

19

Phenyllactate and Phenylacetate

Formed from build-up of Phe due to defective Phenylalanine Hydroxylase

Disrupts neurotransmission and blocks AA transport in brain

Phenyllactate causes musty odor in urine

20

Tetrahydrobiopterin

Cofactor of Phenylalanine Hydroxylase. Deficiency in tetrahydrobiopterin results in Phenylalanine build-up —> PKU

21

Tryptophan derivatives

Trp —> Serotonin —> Melatonin (sleep)

Trp —>Niacin —> NAD(P)

*BOTH require Vitamin B6 - Pyrodoxal

22

Tyrosine Derivatives

Tyr —> Dopamine —> Norephinephrine —> Epinephrine

Tyr —> Thyroid hormones (T3 / T4)

Tyr—> Melanin (pigments)

23

Serine Derivative

Acetylcholine

24

Albinism

Due to a severe lack of melanin

Conversion of Tyrosine —> melanin is blocked by defective enzyme

Complete absence of pigmentation in the skin, hair and eyes

25

Thyroglobulin

Protein made by the thyroid used to produce T3 and T4 hormones
-Some of its tyrosine residues can be iodinated to produce T3 and T4

Hyperthyroidism patients treated with agents that block iodination of Tyr residues —> Decreased production of T4 and T3

26

AA used in removal of nitrogen

Brain: Glu, Gln

Other tissue: Gln, Ala

Connects to urea cycle for excretion from the body

27

Ammonia Toxicity

Excessive ammonia due to disorders in the urea cycle - can have highly toxic effects on brain/CNS
- cerebral edema or intracranial hypertension

NH3 can permeate membranes —> Toxic

NH3 causes pH imbalance

28

Urea cycle relation to high protein diet

High protein diet increases urea production (due to large nitrogen intake).
-20-30% of our urea is hydrolyzed in the GI tract by bacteria, providing a source of nitrogen salvage for gut bacteria
-High protein diet enhances production of urea as well as gut bacteria hydrolysis of urea

29

Creatine

Creatine made from Arg, Gly, Met

30

Phosphocreatine (creatine phosphate)

Serves as a storage form of energy in muscle, brain and sperm. It can quickly generate ATP

31

Creatinine

Small amount of creatinine phosphate non-enzymatically converted to creatinine.
-excreted in urine
-Great marker to check in serum levels to indicate any kidney dysfunction or muscle degeneration