Protein2

Protein2 - 1 Protein Metabolism Objectives Learn the...

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Unformatted text preview: 1 Protein Metabolism Objectives Learn the metabolic fates and regulation of amino acids Use albumin, the acute phase response, creatine, glutamine and collagen as examples of protein function Describe deamination and the urea cycle 2 3 Overview of protein metabolism PROTEIN METABOLISM Food Protein amino acids amino acids L i v e r amino acids undigested protein feces I n t e s t i n e P o r t a l b l o o d small storage pool special pathways to be used in sythesis of nitrogen containing compounds Tissue Protein adreno corticoids insufficient calories hyperthyroidism some tumors ample calories (glucose) insulin growth hormones essential amino acid androgens B l o o d amino acids K i d n e y (deamination) NH 3 (Urine) Purines urin acid (urine) Transamination with amino acids nonessential amino acids NH 3 urea (urine) Deamination -ketoacids Carbohydrate intermediates (glucogenic acids) glycogen Fat intermediates (ketogenic amino acids) Fatty acid Fat Kreb's cycle CO 2 + H 2 O 4 Fate of Dietary Amino Acids - 1 About 20-25% a.a. taken up by liver systemic circulation Will be taken up by other tissues 70% are branched chain a.a. (BCAA) Liver has a low ability to oxidize BCAA Most BCAA muscle About 20% used in liver new proteins 14% used in liver 6% sent into the plasma Albumin, transthyretin (prealbumin), apoproteins, transferrin, ceruloplasmin, prothrombin, etc. 5 Fate of Dietary Amino Acids - 2 About 55-65% of a.a. in liver from portal vein are catabolized Assumes normal protein intake in an average meal More than what is needed for normal metabolism Increased if meal is high in protein and decreased if meal is low in protein Liver obtains about 50% of energy from catabolism of a.a. 6 Factors Promoting Extrahepatic Uptake of Amino Acids Ample calories Amino acids will not need to be used for energy sources Insulin Growth hormone Good essential a.a. pattern Androgens 7 Protein Degradation Normal turnover Few hours to weeks, months, years Depends upon the protein and the tissue Red cells turnover in about 120 days in adults Degradation in extrahepatic tissues Mobilizes protein to a.a. Rate increased by: Cortisol Decreased calories Hyperthyroidism Some tumors Oxidized, damaged, misfolded protein, etc. 8 Protein Degradation & Resynthesis In 70 kg man, ~ 12 kg protein About half each in muscle and nonmuscle About 250 gm turnover daily in healthy adults (range 200 to 400+ gm) Turnover highest in infants, lowest in elderly Turnover Half in liver and intestine About 25% in muscle Rest is in erythrocytes, white cells, digestive enzymes, protein secretions, immune related cells, etc....
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Protein2 - 1 Protein Metabolism Objectives Learn the...

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