Lecture_R - Amino Acid Metabolism. Part I. Learning...

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Amino Acid Metabolism. Part I. • Turnover of proteins • Transamination and oxidative deamination • Toxicity of Ammonia Learning Objectives Extracellular and intracellular degradation of proteins
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Proteins Turnover • The major part of the cell’s amino acids is incorporated in proteins. • There is no storage pool for amino acids analogous to that for glucose (glycogen) or fat acids (triacylglycerols). • If the dietary protein exceeds the body’s need of amino acids, the excess amino acids are converted in metabolic fuels. • Proteins are constantly synthesized and degraded by the cell. This process is necessary for: - Storage of amino acids in the form of dynamic pool; - Elimination of abnormal proteins that may randomly arise from normal proteins because of thermal motion; - Elimination of excessive enzymes, regulatory and transport proteins, a part of metabolic control.
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Half-Life Time of Some Proteins Protein Half-life time, h Ornithine decarboxylase 0.2 PEP carboxylase 5.0 Aldolase 118 Cytochrome c 150 • Enzymes with the short lifetime are at the important points of metabolic control • Enzymes with the long lifetime have constant catalytic activities
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Lysosomes • Lysosomes are organelles containing around 50 hydrolytic enzymes involved in intracellular digestion. • Inside the lysosome, pH 5; cytosolic pH 7. Lysosomal [H + ] is 100 times higher than the cytosolic [H + ]. • Enzymes of the lysosome have optimal rate at acidic pH.
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Lecture_R - Amino Acid Metabolism. Part I. Learning...

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