Term
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Definition
| theres no storing site in mammals and so constant intake/excretion is needed. amino acid pool maintained by intake of protein, AA degraded proteins, and de novo synthesis of amino acids. Mammals only make half the AAs they need; rest are essential from diet |
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Term
| positive and negative nitrogen balance |
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Definition
| positive = growth and incorperation, negative results from starvation where breakdown of skeletal muscle occurs |
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Term
| fates of amino acid carbon skeletons - carbon skeleton is converted to what? |
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Definition
| pyruvate, TCA intermediates. Acetyl-CoA or acetoacetyl CoA |
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Term
| nutritional protein deficiencies |
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Definition
| decreased body protein, energy stores, and micronutrients. Secondary to weight loss, restricted diet, illness etc. MARASMUS - general starving - deficiency of protein and body fat |
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Term
| distended abdomen in underdeveloped areas results from |
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Definition
| hypoproteinemia, hypoalbuminemia, hepatomegaly from enlarged fatty liver from carbohydrate diet |
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Term
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Definition
| protein content regulated by rate of syntehsis and rate of breakdown...protein half-life can be minutes to years. |
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Term
| two major mechanisms for controlled recylcing of proteins |
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Definition
| 1: ubiquitin-proteosome system (UPS) in cytosol - ATP dependent. and 2: lysosomal degradative enzymes - ATP INDEPENDENT |
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Term
| dietary protein digestion |
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Definition
| protein is degraded by pepsin in stomach. inactive zymogens released from pancreas upon stimulation. Active pacreatic enzymes in small intestine degrade protien and other substrates. Further idgestion of protein to amino acids mediated by enterocytes |
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Term
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Definition
| proteins intiially digested by pepsin in stomach. Pancreatic proteases in lumen of small intestine digest further. Aminopeptidases in intestinal epithelium digest peptides. Amino acids, di- and tri- peptides are trasnported into intestinal epithelial cel. Intracellular peptidases degrade peptides and free amino acids are released into blood |
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Term
| movment of nitrogen in relation to alpha-ketoglutarate |
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Definition
| AKG is a major acceptor of amino groups in the cell. Accepts up to 2 amino groups (AKG --> glutamate --> glutamine). so in NH4+ excess, AKG is depleted which affects TCA and the energy production of the cell |
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Term
| major enzymes involved in amino group transfer to AKG include |
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Definition
| 2 aminotransferases (ALT, AST), glutamate dehydrogenase, glutamine synthetase, glutaminase |
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Term
| transaminations by aminotransferases |
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Definition
| aminotransferases catalyze transfer of alpha-amino group of alpha-amino acid to alpha-carbon of alpha-keto acid |
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Term
| PLP role in aminotransfer |
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Definition
| pyridoxal phosphate synthesized from pyridoxine (vit B6). considered an energy releasing vitamin because of its role in producing AKG from amino acids. Cofactor for >100 enzymes in amino acid metabolism. PlP involved in heme synthesis, neruotransmitter syntehsis, amino acid decarboxylations and other metabolic reactions |
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Term
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Definition
| alanine aminotransferase....glutamate + pyruvate == alpha-KG + alanine |
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Term
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Definition
| aspartate aminotransferase...glutamate + OAA == alpha-KG + aspartate |
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Term
| significance of ALT and AST |
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Definition
| increase can cause liver disease. common cuases of increased serum ALT and AST = viral hepatitis, alcoholic hepatitis, nonalcoholic steatohepatitis |
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Term
| AST significant in these tissues |
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Definition
| cyto and mito forms; heart, liver, skeletal muscle, kidney |
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Term
| ALT significant in these tissues |
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Definition
| cyto form only; liver, kidney, so more "liver-specific" |
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Term
| glutamate dehydrogenase as a key player in metabolism |
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Definition
| enzyme catalyzes oxidative deamination of glutamate. Allosteric enzyme with a pivotal role in metabolism as ADP indicates low cellular energy which stimulates reaction in direction of AKG...and GTP indicates high cellular energy which inhibits reaction in direction of AKG. AKG used in TCA an gluconeogenesis |
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Term
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Definition
| Gln = nitrogen donor in biosynthetic reaction. Ammonia is toxic to tissues so glutamine is a major transporter of ammonia. glutaminase is active in liver mitochondria and glutamine synthetase requires ATP |
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Term
| metabolic role of glutaminase |
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Definition
| in liver mitochondria = glutaminase relesaes amide nitrogen of Gln and NH4+ and also as another function, further deaminates glutamate to yield alpha-ketoglutarate (AKG) |
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Term
| glucose-alanine cycle in muscle protein breakdown |
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Definition
| need to remove amino groups from amino acids released from protein and need to supply glucose to muscle |
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Term
| glucose-alanine cycle in movement of alanine |
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Definition
| pyruvate from muscle --> alanine....alanine carried to liver as alanine has a more minor role in blood nitrogen transport |
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Term
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Definition
| nitrogen removed from the body via urea, which is an uncharged and highly water soluble molecule. |
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Term
| major player enzymes in urea cycle |
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Definition
| carbamoyl phosphate synthetase, ornithine transcarbamylase, argininosuccinate synthase, argininosuccinate lyase, arginase |
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Term
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Definition
| formation of urea in liver is most important way to remove nitrogen. The urea travels from liver to blood. Urea ends up in renal filtrate and is reabsorbed or excreted. Urea in intestine is degraded to CO2 and NH3 by bacterial urease |
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Term
| what happens to systemic urea when renal failure occurs |
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Definition
| more urea ends up in the intestine and bacterial generation of ammonia can contribute to hyperammonemia |
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Term
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Definition
| a high concentration of nitrogen-containing compounds in the blood. INcludes urea, creatinine, uric acids, and other N-containing compounds |
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Term
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Definition
| increased urea in blood. Decline in renal function in associated with fluid, electrolyte, hormonal and other metabolic abnormalitites |
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Term
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Definition
| hyperammonemia could result from compromised liver function, kidney failure or urea cycle enzyme defects resulting in neurotoxicity. Molecular basis of ammonia toxicity not entirely elucidated, but two models have been proposed |
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