Biochemistry: Protein Metabolism Abnormalities

Amino Acids and Protein Synthesis

• Amino acids are the building blocks of protein synthesis, serving as structural elements and energy sources for cells.
• They are necessary for normal cell growth, differentiation, and function.
• There are 22 alpha-amino acids, 20 of which are involved in protein synthesis.
• Amino acids can be divided into α-, β-, γ-, δ- amino acids based on the position of their functional groups.

Amino Acid Metabolism

• Amino acids are involved in biosynthesis, neurotic transmission, and other life processes.
• Peptide bonds link amino acids to form polypeptide chains, which undergo post-translational modifications and sometimes combine to form proteins.
• Nine amino acids cannot be synthesized from other compounds and must be obtained from food; these are essential amino acids.
• Amino acids can be oxidized to urea and carbon dioxide as energy sources through oxidative pathways.

Amino Acid Oxidation Pathway

• The oxidation pathway begins with aminotransferase-mediated deamination, transferring the amino group to alpha-ketoglutaric acid to form glutamate.
• Glutamate enters the urea cycle, while keto acid enters the citric acid cycle to provide energy for life activities.

Amino Acid Transporters (AATs)

• Amino acids are taken up by cells or organelles through the participation of AATs.
• Different amino acids depend on specific AATs, but amino acids and transporters are not one-to-one matched.
• AATs also function as probes for sensing amino acid levels and initiators of nutritional signals.

Classification of AATs

• AATs can be divided into neutral, basic, and acidic categories, with further subcategories, including sodium-dependent and sodium-independent types.

Overview of Amino Acid Metabolism

• The human body can obtain amino acids through food digestion and absorption, tissue decomposition, and internal synthesis.
• Amino acids can be deacidified to produce amino and carbon dioxide, participate in the synthesis of nitrogenous compounds, or undergo deamination to produce α-ketoacid and NH3.

Metabolism of Protein Abnormalities

• Hereditary disorders of amino acid processing can result from defects in the breakdown of amino acids or the body's ability to get amino acids into cells.
• Abnormalities in protein metabolism can refer to various hereditary disorders that affect how proteins are processed in the body.