Amino Acids Flashcards
Amino acid structure
NH2CHCOOHR
Zwitterion form in body
L-amino acids in proteins
Amino Acid Classification
- Nonpolar aliphatic
- Aromatic
- Sulfur containing
- Polar, uncharged
- Charged
Nonpolar aliphatic
Gly, Ala, Pro (cyclic), Val (branched), Leu (branched), Ile (branched)
- hydrophobic
- Clinical correlation: Maple syrup urine (MSU) disease
- can’t break down BCAA -> neurotoxicity
- sweet odor in urine
- Tx: special diet
Aromatic
Phe, Tyr, Trp
- hydrophobic
- Tyr and Trp can H-bond
- Clinical correlation:
1. Phenylketonuria (PKU) disease- can’t break down Phe
2. Precursors: Try -> catecholamines, Trp -> serotonin
Sulfur containing
Met- methyl group donor in methylation rxns
Cys- disulfide bonds
*Clinical correlation: Cystinuria
-defect in Cys transport -> kidney stones
Polar, uncharged
Ash, Gln, Ser, Thr
- hydrophilic
- H-bonds
- can be modified
Charged
Asp (-), Glu (-), His (+), Arg (+), Lys (+)
- ionic interactions
- hydrophilic
- very reactive
- complicated titration
Amino acid modification
- Carb addition
- Lipid addition
- Regulation
- Modified
Carbohydrate addition
- Added to -OH of ser, thr, tyr
* added to NH2 of Asn
Lipid addition
To internal -SH of cys
NH of N-terminal gly
Prenylation: SH of cys
Regulation
- Phosphorylation: -OH for ser, thr, tyr
- acetylation: NH2 of lys, N-terminus
- ADP-ribosylation: N of arg, gln, S of cys
Modified amino acids
- oxidation: pro and lys
* carboxylation: glu
Nonessential
Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, Pro, Ser, Tyr
Essential amino acids
Phe, Val, Thr, Trp, Ile, Met, His, Lys, Leu
Glucogenic amino acids
Nonessential
*Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, Pro, Ser
Essential
*His, Met, Thr, Val
