Globulin catabolism

Brambell FW, Hemmings WA, Morris IG. A theoretical model of gamma-globulin catabolism. Nature 1964 203 1352 1. 

Brambell FWR, Hemmings WA, Morris LG. A Theoretical model of T -globulin catabolism. Nature 1964 1352-5. 

Brambell F W, Hemmings W A, Morris I G (1964). A theoretical model of Gamma-Globulin Catabolism. Nature. 203 1352-1354. 

Transferrin (Tf) is a Pj-globulin with a molecular mass of approximately 76 kDa. it is a glycoprotein and is synthesized in the liver. About 20 polymorphic forms of transferrin have been found, it plays a central role in the body s metabolism of iron because it transports iron (2 mol of Fe + per mole of Tf) in the circulation to sites where iron is required, eg, from the gut to the bone marrow and other organs. Approximately 200 billion red blood cells (about 20 mL) are catabolized per day, releasing about 25 mg of iron into the body—most of which will be transported by transferrin. 

In decreasing concentrations, serum immunoglobulins consist predominantly of IgG, IgA and IgM with their subclasses Gi 4, Ai 2 and Mi 2- Quantitative changes of immunoglobuhns are only partially detected using electrophoresis the y-globulin fraction consists predominantly of IgG, while IgA and IgM are detectable in the p- or p/y-fraction. Catabolization of IgG depends on the respective immunoglobulin concentration, while IgM and IgA are catabolized independently of the sermn level. The half-hfe of IgG is 9—23 days, of IgA 6 days and of IgM 5 days. 

Ceruloplasmin, first reported by Holmberg and Laurrell (47), is a copper-alpha-2-globulin. It comprises about 95% of the total copper body pool and is released only when the protein molecule is catabolized. This fraction of copper is in an exchangeable equilibrium with the ionic form the remainder is loosely bound to albumin (48) and to amino acids (49). This last fraction recently has been reported to play a major role in transporting copper in the body. 

Immediately after an injury, there is loss of fluid to extravascular tissue with a resulting decrease in plasma volume. If the decrease is enough to impair circulation, glomerular filtration is diminished. Diminished renal function leads to the accumulation of urea and other end products of protein metabolism in the circulation. In burned patients, serum total protein concentration falls by as much as 0.8g/dL became of both loss to extravascular spaces and catabolism of protein. Serum aj-, tt2-, and y-globulin concentrations increase, but not enough to compensate for the reduced albumin concentration. The plasma fibrinogen concentration responds dramatically to trauma and may double in 2 to 8 days after surgery. The concentration of C-reactive protein rises at the same time. 

Since this paper went to press a noteworthy publication by J. W. L. Davies, S.-O. Liljedahl, and G. Birke has appeared in Injury, 1, 43 (1969). Nineteen patients with bums of varying sizes were treated in a warm (32°C), dry environment and another group of 41 with similar sized bums in a cooler (22°C), more moist environment. Those in the warm, dry environment showed smaller losses of body weight while in the hospital, with significant reductions in basal metabolic rate and the rate of catabolism of plasma albumin and y-G-globulin, smaller amounts of protein in the extravascular space, increased serum albumin concentrations, a greater rate of synthesis of albumin, and a lower rate of synthesis of y-G-globulin. Less protein was lost in the exudate when the patients were exposed in the warm, dry environment and their clinical condition was often better than those in the normal hospital environment. 

Plasma protein concentrations are dynamic parameters that depend on the biosynthesis, distribution between intravascular and extravascular fluid compartments, and elimination (degradation, catabolism, and loss) of the proteins. Table 8.3 lists some of the common causes for changes of plasma protein and albumin concentrations. A rise in plasma albumin is often due to dehydration, and this can be confirmed by associated increases of plasma globulins, blood hemoglobin, and hematocrit (packed cell volume). 

Most of the plasma proteins are glycoproteins and, except for the ) globulins that are synthesized in lymphoid tissue and the widely distributed cells of the reticuloendothelial system, they are synthesized in the liver. They exist in equilibrium with the tissue proteins and are subject to continuous catabolism and replacement. Nevertheless, homologous plasma proteins (i.e. plasma proteins derived from the same species) appear able to pass into the tissue cells without prior degradation. No particular organ has been shown to be the sole site of catabolism of any one plasma protein. 

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