Lecture 1

Chapters 1 and 2

Alanine

• Ala

• A

• Hydrophobic

• Prominent in the transport of nitrogen from muscle to liver during fasting (Alanine Cycle)

Glycine

• Gly

• G

• Hydrophobic

Valine

• Val

• V

• Hydrophobic

• Branched-chain amino acids

• Metabolism altered in maple syrup urine disease

Leucine

• Leu

• L

• Hydrophobic

• Branched-chain amino acids

• Metabolism altered in maple syrup urine disease

Isoleucine

• Ile

• I

• Hydrophobic

• Branched-chain amino acids

• Metabolism altered in maple syrup urine disease

Proline

• Pro

• P

• Hydrophobic

• Helix breaker

Phenylalanine

• Phe

• F

• Hydrophobic

• Aromatic amino acids

• Increased in phenylalanine hydroxylase deficiency (phenylketonuria ; PKU)

• Intraconversior - inability to synthesize tyrosine from phenylalanine

Tyrosine

• Tyr

• Y

• Hydrophobic

• Aromatic amino acids

• Precursor to dopamine and catecholamines (neurohormones for stress response)

• Can be phoshorylated

  • By action of tyrosine kinases

Tryptophan

• Trp

• W

• Hydrophobic

• Precursor for serotonin and melatonin

  • Can be converted to niacin

Methionine

• Met

• M

• Hydrophobic

• Sulfur containing amino acid

• First amino acid incorporated into polypeptides

• Is the cite of cyanogen bromide cleavage in proteins

Serine

• Ser

• S

• Hydrophilic

• Phosphorylated

Threonine

• Thr

• T

• Hydrophilic

• Phosphorylated

Cysteine

• Cys

• C

• Hydrophilic

• Sulfur-containing amino acid

• Is a component of glutathione, a recyclable antioxidant in cells

Aspartate

• Asp

• D

• Hydrophilic

• Interconverted with oxaloacetate by aspartate aminotransferase (AST)

Glutamate

• Glu

• E

• Hydrophilic

• Intrerconverted with 𝞪-ketoglutarate by alaine aminotransferase (ALT)

Asparagine

• Asn

• N

• Hydrophilic

• Polar, neutral amino acids

Glutamine

• Gln

• Q

• Hydrophilic

• Polar, neutral amino acids

• Formed by glutamine synthetase action in the brain and live to detoxify ammonia

• Serves as a donor of amide nitrogen in the biosynthesis of purines and pyrimidines

Lysine

• Lys

• K

• Hydrophilic

• Basic amino acids and carry positive charge at pH 7

• Site of cleavage by the protease, trypsin in proteins

• Present at high concentration in histones

Histidine

• His

• H

• Hydrophilic

• Only weakly basic and is uncharges at pH 7

• Forms one of the six coordination bonds with Fe+2 in the heme prosthetic group of hemoglobin and myoglobin

Arginine

• Arg

• R

• Hydrophilic

• Site of cleavage by the protease, trypsin in proteins

• Present at high concentration in histones

• pK3 ~ 14

• Always has a positive charge at neutral pH

• It has an important role in the binding of anionic molecules (such as nucleic acids)