CC LEC: AMINO ACIDS AND PROTEINS

• Amino acids


  Small biomolecules containing at least one amino group and one carboxyl group bonded to the alpha-carbon

  
• Parts of amino acids

  • Amino group
  • Carboxylic acid group
  • Side chain or R group
  • Hydrogen atom
  • Alpha carbon

  
• Amino acid abbreviations

  • Ala - Alanine
  • Arg - Arginine
  • Asp - Aspartic acid
  • Asn - Asparagine
  • Cys - Cysteine
  • Gln - Glutamine
  • Glu - Glutamic acid
  • Gly - Glycine
  • His - Histidine
  • Ile - Isoleucine
  • Leu - Leucine
  • Lys - Lysine
  • Met - Methionine
  • Phe - Phenylalanine
  • Pro - Proline
  • Ser - Serine
  • Thr - Threonine
  • Trp - Tryptophan
  • Tyr - Tyrosine
  • Val - Valine

  
• There are 22 amino acids, with 20 established and 2 additional (selenocysteine and pyrrolysine)

  
• Amino acid classifications by side chain polarity


  • Nonpolar hydrophobic
  • Polar uncharged
  • Polar acidic
  • Polar basic

  
• Essential amino acids

  • Phenylalanine
  • Valine
  • Threonine
  • Tryptophan
  • Isoleucine
  • Methionine
  • Histidine
  • Leucine
  • Lysine
  • Arginine

  
• Nonessential amino acids


  • Alanine
  • Asparagine
  • Aspartic Acid
  • Cysteine
  • Glutamic Acid
  • Glutamine
  • Glycine
  • Proline
  • Serine
  • Tyrosine
• Arginine


  • Plays a role in cell division
  • Healing of wounds, stimulation of protein synthesis
  • Immune function
  • Release of hormones
  • Required for the generation of urea and synthesis of creatine
• Histidine


  • Direct precursor of histamine
  • Repair body tissues
  • Maintain myelin sheaths that protect nerve cells
  • Helps manufacture RBC and WBC
  • Protect the body from heavy metal toxicity
• Isoleucine


  • Needed for hemoglobin formation
  • Helps to regulate blood glucose levels and maintain energy levels
• Leucine


  • Boosts the healing of muscle, skin and bones
  • Aids in recovery from surgery
  • Lowers blood glucose levels
  • Optimal growth of infants and for nitrogen balance in adults
• Lysine


  • Plays a role in the production of antibodies and lowers triglyceride levels
  • Needed for proper growth and bone development in children and to maintain a proper nitrogen balance in adults
  • Helps in absorption of calcium and formation of collagen

  
• Methionine


  • Helps initiate translation of messenger RNA
  • Source of sulfur
  • Assists the breakdown of fats
  • Helps to detoxify lead and other heavy metals
  • Helps diminish muscle weakness
  • Prevents brittle hair

  
• Phenylalanine


  • Promotes alertness and vitality, elevates mood, decreases pain, aids memory and learning
  • Used to treat arthritis and depression
  • Used by the brain to produce norepinephrine
  • Uses active transport channel to cross the BBB
  • Interferes with production of serotonin
  • Part of the composition of aspartame
• Threonine


  • Important component in the formation of protein, collagen, elastin and tooth enamel
  • Helps maintain proper protein balance and aids liver function, metabolism and assimilation

  
• Tryptophan


  • Precursor for serotonin and melatonin
  • Natural relaxant
  • Alleviate insomnia by inducing sleep, soothes anxiety and reduces depression
  • Used in treatment of migraine headaches
  • Aids in weight control by reducing appetite
  • Helps control hyperactivity in children
• Valine


  • Needed for muscle metabolism and coordination, tissue repair and maintenance of nitrogen balance
  • Used by muscle tissue as an energy source
  • Used in the treatments for muscle, mental and emotional problems (insomnia, anxiety, liver and gallbladder disease)
• Alanine


  • Involved in the breakdown of glucose
  • Product of the breakdown of DNA
  • Transfer of nitrogen form the peripheral tissue to the liver
  • Helps in reducing the buildup of toxic substances that are released into muscle cells
  • Strengthens the immune system through production of antibodies
• Asparagine


  • First amino acid to be isolated
  • Isolated From asparagus juice
  • Converting one amino acid into another via amination and transamination
  • Required by the nervous system and synthesis of ammonia

  
• Aspartic Acid


  • A metabolite in the urea cycle and participates in gluconeogenesis
• Cysteine


  • Cysteine will travel inside your cells and then as it goes inside the cells, cysteine will be reduced to 2 Cysteine molecules
  • Side-chain that contains sulfur: Cysteine and Methionine
  • Production of flavors

  
• Glutamic Acid


  • Serves as a neurotransmitter and dysregulation have been linked to epileptic seizures
  • Aids in transporting potassium to the spinal fluid
  • Responsible for the taste of umami
  • Food additive/food enhancer (sodium salt, monosodium glutamate)
• Glutamine


  • Most abundant amino acid in the body
  • Assists in maintaining the proper acid/alkaline balance in the body
  • Provides fuel for a healthy digestive tract
  • Supplement used for muscle growth in weightlifting and bodybuilding
  • Transports ammonia to the liver
• Glycine


  • Simplest amino acid
  • Only amino acid not optically active because it has no stereoisomers
  • Has a sweet taste and is used as a sweetener
  • Inhibitory neurotransmitter in the CNS
  • Helps in the synthesis of bile acids
  • Retards muscle degeneration, improves glycogen storage, and promotes healing

  
• Proline


  • Precursor of hydroxyproline
  • Role in wound healing and molecular recognition
  • Works with Vit. C to promote healthy connective tissues
  • Technically not a protein since it is an Imino acid due to its cyclic structure
• Serine


  • Needed for proper metabolism of fats and fatty acids
  • Highly concentrated in all cell membranes
  • Component of the protective myelin sheaths surrounding nerve fibers
• Tyrosine


  • Precursor of epinephrine, norepinephrine, dopamine, T3 and T4
  • Stimulates metabolism
  • Mood elevator, suppresses appetite and helps reduce body fat
  • Treatment of chronic fatigue, narcolepsy, anxiety, depression, low sex drive, allergies and headaches
• Selenocysteine


  Selenium analogue of cysteine, encoded by UGA codon, found in some enzymes

  
• Pyrrolysine


  Encoded by UAG codon, used by archaea and unicellular organisms

  
• Metabolism of amino acids

  1. Ingestion of protein

  2. Digestion by pepsin and trypsin

  3. Absorption of amino acids in intestine

  4. Amino acid pool

  5. Degradation of amino acids - ketogenic or glucogenic

  
• Ketogenic amino acids


  Degradation products are Acetoacetyl-CoA or Acetyl-CoA
• Stop codons are still capable of encoding amino acids
• Stop codons


  Used by archaea and unicellular organisms
• Amino acids are found in the food we eat in the form of proteins
• Protein digestion

  1. Proteins are initially digested by the enzymes pepsin and trypsin

  2. Proteins are degraded into amino acids
• Amino acid pool


  Source of amino acids utilized in translation
• Products of amino acid degradation

  • Acetoacetyl-CoA
  • Acetyl-CoA
  • Pyruvate
  • Citric acid cycle intermediates

  
• Ketogenic amino acids


  When degraded, the products are Acetoacetyl-CoA or Acetyl-CoA
• Glucogenic amino acids


  When degraded, they can generate precursors of glucose like pyruvate

  
• Amino acid metabolism


  1. Amino group is removed through oxidative deamination or transamination

  2. Keto acid enters common metabolic pathway

  3. Toxic ammonia is converted to less toxic urea