CHEMICAL CHARACTERIZATION OF GLYCOPEPTIDES FROM HUMAN ΓM-Globulins

Abstract

The three major classes of immunoglobulins 3'G, 3'A, and ~M contain different amounts of carbohydrate. Considerable data are now available on the number and location of the carbohydrate units on the polypeptide chains of ~/Gglobulins, but as yet little information exists for 3'M. The 3,M-globulins have approximately 10% of their mass made up of carbohydrate. In spite of this large mass, neither distribution, linkage, location, nor functional importance of this moiety is known. Among the several reasons for this paucity of information is the difficulty in securing large amounts of pure 3,M-globulin, plus the problems in structural analysis of complex oligosaccharides.The present study is devoted to two aspects of the chemistry of the carbohydrate moiety of 3'M. First is a survey of the carbohydrate composition of several pathological macroglobulins to investigate its constancy of composition. This study demonstrates that macroglobulins can be divided into at least two major groups on the basis of their carbohydrate composition. Second is a study in detail of the carbohydrate portions from highly purified macroglobulins of each group with a view to defining carbohydrate units, including their size and number, as they appear on the parent molecule. Materials and MethodsPreparation of "gM-Globulin.--Serum was obtained in the course of plasmapheresis therapy of patients with WaldenstrSm's macroglobulinemia. Sera, selected for euglobulin properties, were either diluted in ten-fold their volumes of distilled water or dialyzed against 1000-fold their volumes of 0.0015 M phosphate, pH 6.0. The centrifuged euglobulin precipitate was dissolved in neutral phosphate-buffered saline, and the solution was cleared by high speed centrifugation or filtration through Millipore filters. Small molecular weight contaminants were removed by filtration through a calibrated column of Sephadex G-200 having a total

The oligosaccharide units of a human type L immunoglobulin M (macroglobulin)

“…Glycopeptides la and lb have slightly different compositions, accounting for their different electrophoretic mobilities. The compositions of Don IgM glycopeptides are similar to those reported by Davie & Osterland (1968), but show less variability in the monosaccharide content.…”

“…The macroglobulins were found to contain six of the former type of unit and from two to four of the latter (Spragg & Clamp, 1969 been reported by JOuanneau, Razafimahaleo & l3ourrillon (1970). Davie & Osterland (1968) isolated three Protase glycopeptides from each of two macroglobulins, and calculated that both proteins contained eight oligosaccharide units. Miller (1970) isolated glycopeptides by exclusion chromatography of trypsin and Pronase digests of madroglobulins, but the number of oligosaccharide units in the proteins was not estimated.…”

Purification and characterization of two classes of immunoglobulins from the marine toad, Bufo marinus

“…The two molecules were also found to differ in the amount, as well as composition, of carbohydrate. The carbohydrate content of the immune macroglobulin (7.6%) is in the range of values (7.3-12.9%) reported for human macroglobulins by Davie and Osterland (1968). The low molecular weight antibody has a content of 4.2% which is significantly higher than values reported for IgG from several species of mammals by Niedermeier et al (1971).…”

Recognition of Two Distinct Groups of Human IgM and IgA Based on Different Binding to Staphylococci

“…There may be one or more alleles of either type, but this does not affect the calculations. The frequency of allele(s) coding for nonbinding molecules is p. [2] The frequency of binding and nonbinding in monoclonal proteins reflect the frequencies of the corresponding genes.…”