Papain fragments

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.

Heavy meromyosin (HMM molecular mass about 340 kDa) is a soluble protein that has both a fibrous portion and a globular portion (Figure 49-4). It exhibits ATPase activity and binds to F-actin. Digestion of HMM with papain generates two subfragments, S-1 and S-2. The S-2 fragment is fibrous in character, has no ATPase activity, and does not bind to F-actin. 

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 ... 

Figure 20.11 Papain digestion of IgG antibodies primarily results in cleavage in the hinge region above the interchain disulfides. This produces two heavy-light chain pairs, called Fab fragments, each containing one antigen binding site. The Fc region normally can be recovered intact.

Fab fragment containing amine groups (from papain digestion of IgG)... 

Figure 4.5. Structure of myosin. Myosin comprises both light and heavy chains. The heavy chains may be cleaved by trypsin to generate light meromyosin (LMM) and heavy mero-myosin (HMM). Papain digestion of HMM yields subfragments SI and S2 each SI fragment contains an ATPase site and an actin-binding site. The light chains modify the activity of the ATPase.

A family of 100 hybridoma antibodies can typically provide 20 tight binders and these need to be assayed for catalysis. At this stage in the production of an abzyme, the benefit of a sensitive, direct screen for product formation comes into its own. Following identification of a successful catalyst, the antibody is usually recloned to ensure purity and stabilization of the clone, then protein is produced in larger amount (—10 mg) and used for determination of the kinetics and mechanism of the catalysed process by classical biochemistry. Digestion of such protein with trypsin or papain provides fragment antibodies, Fabs, that contain only the attenuated upper limbs of the intact IgG (Fig. 1). It is these components that have been crystallized, in some... 

An antibody can be cleaved by enzymes such as papain and pepsin into different fragments (Fig. 4.2). 

CBH I 497 core-BA aa sequence in part from protein and in full from gene (cbhl), number and location of SS bridges, region of O-glycosylation, types of carbohydrate, papain cleavage site, hydrophobic cluster analysis, computer model of active site, 2D-NMR on a synthetic tail fragment, SAXS on whole CBH I, head domain and xylan/CBH I complex... 

Figure 1. Elution profile of CBH I-papain reaction products on two Superose HPSEC columns (HR 6 12) connected in series. Ilte elution of the tail fragment was confirmed using the phenol-sulfiiric acid assay for carbohydrate.

Since antibodies of different species and different subclasses are variably cleaved by pepsin and papain, a test run is recommended to check incubation time and cleavage conditions. Take samples of different incubation time, freeze rapidly, and monitor the fragmentation by SDS-PAGE at the end of the experiment. Apply the samples both with and without DDT. 

An alternative to the synthesis of proteins by classical fragment synthesis in solution or by solid-phase synthesis on a support is the use of enzyme-catalyzed condensation of amino acids or peptides. This possibility was first demonstrated in 1938 91 with the synthesis of poorly soluble benzoyl-leucyl-leucine anilide by papain catalysis. After many years, this approach was extended to the preparation of peptide hormones such as Leu-enkephalin 92 and dynorphin(l -8).[93 This was made possible by the use of highly purified enzymes and by careful control of reaction conditions. The basic principles of protease-catalyzed peptide bond formation have been discussed.194 ... 

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