Monoclonal antibodies to soluble, human milk galactosyltransferase (lactose synthase A protein)

Monoclonal antibodies have been produced against soluble human milk galactosyltransferase of a blood group O donor. After initial screening by radioimmunoassay, fourteen hybridomas were further characterized by enzyme-linked immunosorbent assay, immunoblotting of purified enzyme following sodium dodecyl sulfate-polyacrylamide gel electrophoresis, enzyme activity modification, and enzyme localization in HeLa cells by immunofluorescence. Of these fourteen clones, seven had titers between 1500 and 7800 as estimated by ELISA. In general, the titer correlated with staining intensity on immunoblots and in immunofluorescence. In the presence of monoclonal antibody, enzyme activity was usually slightly enhanced or stabilized. Subcloning yielded four monoclonal antibody preparations designated as GT2/24/108, GT2/36/118, GT2/61/14, and GT2/77/22, which belong to Ig class G2b, G3, M, and G1, respectively. They all recognized the enzyme in purified form or in defatted milk as a single, broad band on electrophoresis-immunoblotting and produced a concise juxtanuclear fluorescence typical for the Golgi apparatus in HeLa cells.     

Purification and characterization of human serum galactosyltransferase (lactose synthetase A protein)

A galactosyltransferase, which transfers galactose from UDP-galactose to N-acetylglucosamine, was purified 286,000-fold to homogeneity with 40% yield from human plasma by repeated affinity chromatography on alpha-lactalbumin-Sepharose. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme showed a single protein band with molecular weight of 49,000. The enzyme is a glycoprotein with 11% by weight carbohydrate, which seems to have only asparagine-N-acetylglucosamine linkage-type carbohydrate chains. The enzyme showed characteristic changes in activity at different alpha-lactalbumin concentrations, indicating that the enzyme is the A protein of lactose synthetase. Km values for the substrates were found to be 0.056 mM for UDP-galactose, 3.2 mM for GlcNAc, and 0.44 mM for Mn2+, and in the presence of alpha-lactalbumin, 3.4 mM for Glc, and 0.20 mM for Mn2+. The activity of the enzyme was neutralized by anti-enzyme antibody, but the antibody did not neutralize the bovine milk galactosyltransferase (A protein) activity.     

Submicromolar manganese dependence of Golgi vesicular galactosyltransferase (lactose synthetase)

1. Manganese(II) buffers were set up with inorganic triphosphate, trimethylenediaminetetraacetate and tetramethylenediaminetetraacetate to study the Mn dependence of beta 1,4-galactosyltransferase (lactose synthetase) in preparations of rat mammary gland. 2. In intact particulate preparations, treated with the calcium ionophore A23187, lactose synthesis was abolished by chelators and restored by bivalent transition metal ions in a manner characteristic of activation site I of the pure enzyme. Ni(II) also activated, as did Mg at high concentration. 3. Only Mn(II) could restore endogenous rates, giving an apparent Km of 0.1-0.2 microM, and eliciting about 70% full activity without addition of a site II activator. 4. In purified Golgi membrane vesicles, Mn gave an apparent Km of 0.4 microM. This increased sharply to about 10 microM on permeabilization with filipin, lysis with detergents, solubilization with Triton X-100, or in the pure enzyme. Preparations of chemically undamaged Golgi vesicles, known to include a proportion of the enzyme on exposed membranes, exhibited both low-Km and high-Km components. 5. The response of particulate galactosyltransferase to apparently physiological concentrations of free Mn(II) ion is interpreted as either due to a sensitizing factor within the Golgi lumen, or to the accumulation of Mn at elevated concentrations. Alternatively, the high Km of the soluble enzyme may reflect proteolytic damage.     

Electrophoretic characterization of rice varieties using single seed (salt soluble) proteins

Summary Variation of salt soluble protein fractions of seeds has been observed in a number of rice varieties as recorded in their electrophoregram tracings: both qualitative and quantitative differences were present. Analysis of variance has been found to be useful in estimating the quantitative differences. These tracings or patterns appear to be unique for each of the varieties investigated and seem to be genetical in nature as they remain constant under different environmental conditions, and therefore could be conveniently used for variety identification.     

Co-purification of soluble human galactosyltransferase and immunoglobulins

Preparations of human malignant effusion galactosyltransferase activity purified according to previously published techniques using enzyme-specific affinity chromatography consistently produced antibodies directed toward immunoglobulins with no detectable antigalactosyltransferase. Double immunodiffusion analysis of the antigen showed the presence of both IgG and IgA. Affinity chromatography with anti-human IgG-Sepharose and anti-human serum-Sepharose resulted in a 48,000-fold purification of galactosyltransferase activity with no detectable IgG by radioimmunoassay. Immunization of rabbits with this preparation produced antibodies directed against galactosyltransferase activity and minimal anti-Ig. The persistence of immunoglobulins during the purification of soluble galactosyltransferase activity through two enzyme-specific affinity chromatographic steps suggests an association of immunoglobulins with galactosyltransferase activity.     

The analysis of soluble galactosyltransferase isoenzyme patterns using high resolution agarose isoelectricfocusing

A high resolution method has been developed to separate the isoenzymes of galactosyltransferase by combining isoelectricfocusing (IEF) in 245 mm long agarose gels with a highly sensitive enzyme activity assay. The resolution and sensitivity is such that the isoenzyme pattern of 10 microliters human serum can be resolved. Using this method normal human serum was shown to contain at least 12 isoenzyme forms of galactosyltransferase, the major forms having isoelectric points of 4.33, 4.43, 4.51, 4.61, 4.74, 4.87, 4.96, 5.16 and 5.23. Part of the isoenzyme pattern complexity is due to sialylation of some isoenzymes. Alpha-lactalbumin-affinity chromatography, a method widely used in the purification of galactosyltransferase, causes a preferential purification of some of the isoenzyme forms.     

Quantitative immunoassay of total cellular GAP junction protein connexin32 during liver regeneration using antibodies specific to the COOH-terminus.

A radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) were used to determine relative concentrations of liver connexin32 (CX32) in rats. The RIA and ELISA utilize synthetic peptides corresponding to regions of the carboxyl-terminus and antibodies raised in rabbits against these peptides. Assuming that affinities of antisera are similar for peptide and native CX32, total cellular CX32 was found to exceed the amount of gap junction protein at the cell surface calculated from morphometric analyses by 1.5-2.0 fold. This finding raises the possibility that some of the protein is present in cytoplasmic compartments or as occult precursors in the plasma membrane. Studies of CX32 content in regenerating rat liver support this conclusion and show a time course of loss and recovery of CX32 that agrees with those reported in studies using other techniques.     

Cellular localization of water soluble, allergenic proteins in rye-grass (Lolium perenne) pollen using monoclonal and specific IgE antibodies with immunogold probes

Summary A postembedding method has been developed for localizing water soluble allergens in rye-grass pollen. This uses dry fixation in glutaraldehyde vapour, followed by 2,2-dimethoxypropane, prior to a 100% ethanol series leading into embedment in LR Gold. This has allowed the attachment of specific monoclonal antibodies to the allergen, which are themselves probed with specific immunogold labels to the antibodies. Wall and cytoplasmic sites have been identified, representing an improvement of fixation and localization of allergens over previous studies employing polyclonal, broad spectrum antibodies.Rye-grass allergens are labelled in mature pollen grains in the exine (tectum, nexine and central chamber), and in the electron opaque areas of the cytoplasm, especially mitochondria. The allergens are absent from the intine, polysaccharide (P) particles, amyloplasts, Golgi bodies and endoplasmic reticulum. IgE antibodies derived from humans allergic to rye-grass pollen, bind to similar sites in the cytoplasm but only to the outer surface of the pollen grain wall. This method now provides a valuable tool for further developmental studies on the pollen grains, in order to establish the site/s of synthesis of the allergens.