Synthesis of Body Proteins

Exogenous (from food or supplements) and endogenous (from body protein turnover) AAs form the AA pool that serves the body's needs for the synthesis of proteins such as:

  • Enzymes that combine with other molecules in the cells to catalyze chemical reactions that take place in the body
  • Immunoproteins that are involved in identifying and destroying foreign antigens
  • Transport proteins that transport other substances throughout the body
  • Peptide hormones that control many bodily functions, usually by regulating the synthesis or activity of enzymes
  • Structural proteins, including skin, hair, nails, and muscle

Dietary Protein

Protein hormones

Plasma proteins

Tissue proteins

Protein hormones

Plasma proteins

Tissue proteins

Synthesis of non-essential amino acids

Catabolism

Peptide synthesis

Serine -

Tryptophan -

Phenylalanine Tyrosine

Energy

Synthesis of non-essential amino acids

Catabolism m /

Nitrogen

Carbon skeleton

Energy

Sweat, hair, desquamated Fecal ce"s Amino acids nitrogen Ammonia

Peptide synthesis

Serine -

Tryptophan -

Specific —functions of amino acids

Aspartic acid ■

Glutamine -

Glutamic acid T

y-amino butyric aci Glycine

Glutathione Oxytocin, Vasopressin Bradykinin

  • Ethanolamine-— Choline
  • Nicotinic acid
  • Anserine

Aspartic acid ■

Glutamine -

  • 5-Hydroxytryptamine ■ Histamine ^Carnosine —
  • Pyrimidines-Purines-

3-MeHistidine

Phenylalanine Tyrosine

Glycocholic acid Porphyrins

Conjugation-

Creatine -

Choline Adrenaline t

Noradrenaline Thyroid hormones Melanin

Hippuric acid

Creatinine Uric acid Allantoin

Urea

3-Methyl-Histidine

FIGURE 15.6 General features of mammalian protein metabolism. From Shils ME, Young VR, Modern Nutrition in Health and Disease, 7th ed., Philadelphia: Lea & Febiger, 1988. Permission granted by Wolters Kluwer Health.

FIGURE 15.7 Metabolic pathway of AAs. Reprinted with permission from Ajinomoto's Amino Acid Handbook, Japan: Ajinomoto, 2004.
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