Enzymes immunoglobulin

The recognition is the binding of a carbohydrate by a specific receptor, which is usually part of a protein (enzyme, immunoglobulin, lectin). The process is due to the sum of weak interactions (van der Waals-London, hydrogen bonds) that may results in high association constants. 

Method of polyelectrolyte self-assembly was successfully implemented for designing and fabrication of composite sensitive membranes containing different macromolecules, such as organic dyes, enzymes, immunoglobulines. 

The resuspended and formulated Fraction II precipitate normally contains some aggregated IgG and trace substances that can cause hypotensive reactions in patients, such as the enzyme prekail ikrein activator (186). These features restrict this type of product to intramuscular adininistration. Further processing is required if products suitable for intravenous adininistration are required. Processes used for this purpose include treatment at pH 4 with the enzyme pepsin [9001-75-6] being added if necessary (131,184), or further purification by ion-exchange chromatography (44). These and other methods have been fiiUy reviewed (45,185,187,188). Intravenous immunoglobulin products are usually suppHed in the freeze-dried state but a product stable in the solution state is also available (189). 

Most of the known antiparallel p structures, including the immunoglobulins and a number of different enzymes, have barrels that comprise at least one Greek key motif. An example is 7 crystallin, which has two consecutive Greek key motifs in each of two barrel domains. These four motifs are homologous in terms of both their three-dimensional structure and amino acid sequence and are thus evolutionarily related. 

Figure 1S.6 Enzymatic cleavage of immunoglobulin IgG. The enzyme papain splits the molecule in the hinge region, yielding two Fab fragments and one Fc fragment.

Many proteins found in nature are glycoproteins because they contain covalently linked oligo- and polysaccharide groups. The list of known glycoproteins includes structural proteins, enzymes, membrane receptors, transport proteins, and immunoglobulins, among others. In most cases, the precise function of the bound carbohydrate moiety is not understood. 

The fundamental role of blood in the maintenance of homeostasis and the ease with which blood can be obtained have meant that the study of its constituents has been of central importance in the development of biochemistry and clinical biochemistry. The basic properties of a number of plasma proteins, including the immunoglobulins (antibodies), are described in this chapter. Changes in the amounts of various plasma proteins and immunoglobulins occur in many diseases and can be monitored by electrophoresis or other suitable procedures. As indicated in an earlier chapter, alterations of the activities of certain enzymes found in plasma are of diagnostic use in a number of pathologic conditions. 

As depicted in Figure 50-8, digestion of an immunoglobulin by the enzyme papain produces two antigen-binding fragments (Fab) and one crystallizable fragment (Fc), which is responsible for functions of im-... 

IgG consists of four polypeptide subunits held together by disulphide bonds. Native immunoglobulins are rather resistant to proteolytic digestion but certain enzymes have been usefiil in elucidating their structure. Papain cleaves the molecule into three fragments of similar size ... 

In each of the assays of potency the amount of the immunoglobulin and the amount of a corresponding standard preparation that are required to neutralize the infectivity or other biological activity of a defined amount of virus or to neutralize a defined amount of a bacterial toxin are determined. The two determined amounts and the assigned unitage of the standard preparation are then used to calculate the potency of the immunoglobulin in International Units (lU). ELISA, enzyme-linked immunosorbent assay. 

Secondary antibody and determination. A secondary antibody labeled with an enzyme is added which binds to the primary antibody that is bound to the coating antigen. If the primary antibody were produced in a rabbit, an appropriate secondary antibody would be goat anti-rabbit immunoglobulin G (IgG) conjugated with horseradish peroxidase (HRP) (or another enzyme label). Excess secondary antibody is washed away. An appropriate substrate solution is added that will produce a colored or fluorescent product after enzymatic conversion. The amount of enzyme product formed is directly proportional to the amount of first antibody bound to the coating antigen on the plate and is inversely proportional to the amount of analyte in the standards. 

Antiphospholipid antibodies include lupus anticoagulants (LAs) and anticardi-olipin (aCL) antibodies. Lupus anticoagulants are immunoglobulins that are characterized by their ability to inhibit phospholipid-dependent coagulation assays. In contrast, aCL antibodies are measured in an enzyme-linked immunosorbent assay... 

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