Leucine

Notes
biochemistry

Graph

$$\ce{C₆H₁₃NO₂}$$ Leucine

Protein Related Properties

  • High tendency to be in the
    • hydrophobic core of a protein
    • $\alpha$ helics
  • Stabilizes protein structure through hydrophobic interactions
  • Frequently involved in

Metabolic Characteristics

Muscle and Protein Synthesis

  • Most potent amino acid activator of mtorc1
  • Directly stimulates:
    • Muscle protein synthesis (MPS)
    • Ribosomal biogenesis
  • Acts as a nutrient signal, not just a building block
  • Critical for:
    • Muscle growth (hypertrophy)
    • Muscle maintenance
    • Recovery after exercise

Hormonal & Signaling Effects

  • Activates mTOR pathway independent of insulin
  • Enhances insulin secretion (especially with carbohydrates)
  • Influences:
    • Cell growth
    • Cell proliferation
    • autophagy suppression (via mTOR activation)

Physiological Functions

  • Maintains nitrogen balance

  • Supports:

    • Muscle mass preservation
    • Tissue repair

  • Plays a role in:

    • Energy production during fasting/exercise
    • Regulation of satiety and metabolism (via hypothalamic signaling)

Nutritional Characteristics

  • Dietary sources:
    • Meat, poultry, fish
    • Eggs
    • Dairy (whey protein is especially rich)
    • Soy, legumes, nuts (lower amounts)
  • High bioavailability in animal proteins
  • Daily requirement:
    • ~42 mg/kg/day (FAO/WHO estimate for adults)

Clinical & Health Aspects

  • Deficiency symptoms:
    • Muscle wasting
    • Fatigue
    • Poor wound healing
  • Excess intake (rare but possible):
    • May contribute to insulin resistance (chronically high levels)
    • Can exacerbate hepatic encephalopathy in liver disease
  • Related disorder:
    • Maple Syrup Urine Disease (MSUD)
      • Defective BCAA metabolism
      • Leucine accumulation is neurotoxic

Supplementation Characteristics

  • Commonly supplemented as:

    • Free leucine
    • BCAA blends
    • EAA formulas

  • Typical supplemental dose:

    • 2–5 g per serving

  • Often used for:

    • Sarcopenia
    • Athletic performance
    • Recovery support

TODO

read about -  leucine zipper motifs (DNA-binding transcription factors)

  • Initial metabolism via branched-chain aminotransferase (BCAT)

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