Metabolism of proteins

Triiodothyronine (3, 5,3-L-triiodothyronine, T3) is a thyroid hormone. It is producedby outer ring deiodination of thyroxine (T4) in peripheral tissues. The biologic activity of T3 is 3-8 times higher than that of T4. T3 is 99.7% protein-bound and is effective in its free non-protein-bound form. The half-life of triiodothyronine is about 19 h. The daily tur nover of T3 is 75%. Triiodothyronine acts via nuclear receptor binding with subsequent induction of protein synthesis. Effects of thyroid hormones are apparent in almost all organ systems. They include effects on the basal metabolic rate and the metabolisms of proteins, lipids and carbohydrates. 

Insulin, a hormone produced by the pancreas, acts to maintain blood glucose levels within normal limits (60-120 mg/dL). This is accomplished by die release of small amounts of insulin into die bloodstream tiirough-out the day in response to changes in blood glucose levels. Insulin is essential for die utilization of glucose in cellular metabolism and for die proper metabolism of protein and fat. 

Sflf-Test 6.16B Calculate the standard enthalpy of formation of urea, CO(NH2)2, a by-product of the metabolism of proteins, from the information in Tables 6.4 and 6.5. 

Physiological and pathological changes are reflected in the production and the metabolism of proteins and peptides. Such changes are detectable in extracellular fluids, including blood plasma, cerebrospinal fluid, synovial fluid, and urine (Clynen et al 2003). 

Weller M (1979) Protein phosphorylation the nature, function, and metabolism of proteins with covalently bound phosphorus. Pion, London... 

There is no discrete target tissue for thyroid hormones virtually every cell in the body is affected by thyroid hormones in some way. These hormones are intimately involved in the maintenance of normal function in virtually every cell type, including cellular responsiveness to other hormones, to the availability of metabolic substrates, to growth factors, and so on. Thyroid dysfunction can produce dramatic changes in the metabolism of proteins, carbohydrates, and lipids at the cellular level that can have repercussions for the operation of the cardiovascular, gastrointestinal, musculoskeletal, reproductive, and nervous systems. Some of the clinical manifestations of thyroid dysfunction are presented next in the discussions of hypothyroid and hyperthyroid states. 

Mechanism of Action Acts as a coenzyme for various metabolic functions, including metabolism of proteins, carbohydrates, and fats. Aids in the breakdown of glycogen and in the synthesis of gamma-aminobutyric acid in the CNS. Therapeutic Effect Prevents pyridoxine deficiency. Increases the excretion of certain drugs, such as iso-niazid, that are pyridoxine antagonists. 

Figure 5.6. Metabolism of proteins by proteases found at the cell surface and internal cellular organelles. Intracellular uptake of proteins often involved receptor-mediated endocytosis initial surface binding can be specific for a hormone (e.g., insulin, glucagon).

Amitrole had a drastic effect on the fixation of 14C02 by illuminated chloroplasts of Chlorella pyrenaidom, lowering the incorporation into sucrose by 95% at a concentration of 500 mg. per liter it did pot affect phosphorylated compounds.145 Carbohydrates hydrolyzable by acids were higher (51%) in treated, chlorotic corn leaves than in controls (32%), and this result was interpreted as due to increased metabolism of proteins and fats. The respiratory quotient of 0.8 to 0.88, compared to controls near 1.0, supported this interpretation.145... 

The data obtained have shown that l-(chloromethyl)silatrane produces a favourable effect on the physiological processes in the organism of fowl. It increases the viability, stimulates the function of haemopoiesis thus raising the number of erythrocytes and the amount of haemoglobin. Administration of 1-(chloromethyl)silatrane stimulates metabolic reactions in the organism thus increasing the metabolism of protein, lipids, carbohydrates and phosphorus-calcium. 

Increased metabolization of proteins, carbohydrates, fats and micronutrients. 

Experimental results from three species of Black Sea fish exposed in the autumn of 1991 to sudden oxygen deficiency (Stolbov et al., 1995) agree with the data from similar experiments on the same species in spring-early summer 1992 (Stolbov et al., 1997). The only discrepancy was the lower value (30-40%) for the aerobic metabolism of protein. Thus in different seasons and in different physiological states (post-spawning rest in autumn and intensive sexual development in spring) fish maintain the same mode of metabolism of biochemical substrates. 

The anaerobic mode of protein utilization is entirely possible in theory and in practice. Oxygen is not required for protein and nitrogen catabolism until the final stages of amino acid deamination have been reached. Complete anaerobic catabolism of proteins and nitrogen compounds (to the point where the final products C02, HjO and NH3 appear) has been known for a long time in prokaryotic organisms, but in eukaryotes only in parasitic worms, which are obligate anaerobes (von Brand, 1946). However, in recent decades, anaerobic metabolism of proteins has been found in some aquatic... 

Parina, E.V. (1967). Age and Metabolism of Proteins (In Russian). Kharkov State University, Kharkov, 204 pp. 

The distribution and metabolism of protein-based biotech drugs, for example, generally follows the mechanisms of endogenous and nutritional proteins. This includes, for example, unspecific proteolysis as a major elimination pathway for proteins rather than oxidative hepatic metabolism typical for the majority of small-molecule drugs. As a consequence, drug interactions studies focused on cytochrome P-450 enzymes do not usually need to be performed for protein-based biotech drugs [17]. 

An important first step in the hepatic metabolism of proteins and peptides is uptake into the hepatocytes. Small peptides may cross the hepatocyte membrane via passive diffusion if they have sufficient hydrophobicity. Uptake of larger pro-... 

Deen,W.M., M.J. Lazzara, and B.D. Myers. 2001. Structural determinants of glomerular permeability. Am. J. Physiol. Renal Physiol. 281 F579—596. Maack,T., C. Park, and M. Camargo. 1985. Renal filtration, transport and metabolism of proteins. In D. Seldin, and G. Giebisch (Eds.), The Kidney. 

Urea A waste product of the metabolism of proteins that is formed by the liver and eliminated from the body through the kidneys as urine. 

This chapter deals with various aspects of metabolism of protein hormones, in particular, how these regulatory molecules are synthesized and stored as precursor molecules and proteolytically processed to generate biologically active hormones. The mechanisms involved in secretion and degradation are also described. 

Recombinant human growth hormone (hGH) is a 22-kDa protein drug having 191 amino acids. It has been used to treat a number of conditions, including short stature in children, Turner syndrome, and chronic renal failure. It is said to play an important role in the metabolism of proteins, carbohydrates, and fats as well as electrolytes and hence influences weight and height. It has been reported that hGH secretion in humans is pulsatile, showing low basal serum levels in between peaks. It has been... 

The liver orchestrates the metabolism of proteins and amino acids. Most blood proteins (except for antibodies) are synthesised and secreted by the hver. One of the most abundant serum proteins is albumin. Impaired hver function that results in decreased amounts of serum albumin may lead to oedema, swelling due to fluid accumulation in the tissues. 

Bro-Rasmussen, F. (1958) The riboflavin requirement of animals and man and associated metabolic relations. II. Relation of requirement to the metabolism of protein and energy. Nutr. Abst. Rev. 369-86. 

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