Effect of neuraminidase on the chromatographic behaviour of eleven acid hydrolases from human liver and plasma.

1. The elution profiles of eleven acid hydrolases from human liver and plasma were directly compared using a system whereby a single salt gradient was simultaneously applied to two DEAE-cellulose chromatographic columns. 2. Plasma alpha-L-fucosidase, alpha-mannosidase, alpha-galactosidase and alpha-glucosidase isoenzymes were eluted at higher salt concentrations than the corresponding liver isoenzymes whereasbeta-N-acetylglucosaminidase, beta-galactosidase, beta-glucosidase, exo-1,4-beta-xylosidase and alpha-L-arabinofuranosidase isoenzymes were eluted at lower salt concentrations. The elution profiles of beta-glucuronidase and acid phosphatase weremore complex. 3. After incubation with neuraminidase most plasma hydrolases were eluted at lower salt concentrations, however the elution patterns of beta-glucosidase, beta-xylosidase and acid phosphatase were not altered. 4. Preincubation with neuraminidase had no effect on the elution profiles of six liver hydrolases whereas the major isoenzymes of alpha-mannosidase, beta-galactosidase and alpha-L-arabinofuranosidase were eluted at markedly lower salt concentrations. Liver alpha-fucosidase and alpha-galactosidase were eluted at slightly lower salt concentrations afterincubation with neuraminidase. 5. The results are discussed in relation to thepathogenesis of Mucolipidosis II (I-cell disease), and the synthesis and packaging of lysosomal enzymes.     

The minor anionic form of arylsulphatase B (arylsulphatase Bm) of monkey brain. Purification and phosphoprotein nature

The anionic form of arylsulphatase B (arylsulphatase Bm) was purified to apparent homogeneity from monkey brain through steps involving chromatography on diethylaminoethyl-cellulose, Blue-Sepharose, Biogel HTP and finally Biogel P-300 gel filtration. The molecular weight of the purified enzyme as deduced by gel filtration on Biogel P-300 and by sodium dodecylsulphate gel electrophoresis was ∼ 30,000.Escherichia coli alkaline phosphatase treatment of arylsulphatase Bm resulted in the conversion of upto 84% of the enzyme into a less charged form of enzyme, that could not bind to diethylaminoethyl cellulose. Potassium phosphate an inhibitor of alkaline phosphatase prevented this conversion. Upon acid hydrolysis the purified enzyme yielded approximately 7.0 mol of inorganic phosphate per mol of protein.Vibrio cholerae neuraminidase treatment did not alter the charge on arylsulphatase Bm.     

Comparison of human alkaline phosphatase isoenzymes. Structural evidence for three protein classes.

The structural relationships among human alkaline phosphatase isoenzymes from placenta, bone, kidney, liver and intestine were investigated by using three criteria. 1. Immunochemical characterization by using monospecific antisera prepared against either the placental isoenzyme or the liver isoenzyme distinguishes two antigenic groups: bone, kidney and liver isoenzymes cross-react with anti-(liver isoenzyme) serum, and the intestinal and placental isoenzymes cross-react with the anti-(placental isoenzyme) antiserum. 2. High-resolution two-dimensional electrophoresis of the 32P-labelled denatured subunits of each enzyme distinguishes three groups of alkaline phosphatase: (a) the liver, bone and kidney isoenzymes, each with a unique isoelectric point in the native form, can be converted into a single form by treatment with neuraminidase; (b) the placental isoenzyme, whose position also shifts after removal of sialic acid; and (c) the intestinal isoenzyme, which is distinct from all other phosphatases and is unaffected by neuraminidase digestion. 3. Finally, we compare the primary structure of each enzyme by partial proteolytic-peptide 'mapping' in dodecyl sulphate/polyacrylamide gels. These results confirm the primary structural identity of liver and kidney isoenzymes and the non-identity of the placental and intestinal forms. These data provide direct experimental support for the existence of at least three alkaline phosphatase genes.     

The presence of a low molecular weight acid phosphatase in liver tissue that cannot be demonstrated with the histochemical substrate naphthol AS-BI phosphate

Summary Three distinct isoenzymes of acid phosphatase have been separated from extracts of liver tissue of rats by gel filtration. These isoenzymes have molecular weights of 180,000±35,000; 74,000±11,000 and 13,000±2,500. High molecular weight isoenzymes and a low molecular weight isoenzyme of acid phosphatase (molecular weight 13,000±2,100) were also present in extracts of normal human and mouse liver tissue, and of pathologically altered liver tissue of mice in which the activity of acid phosphatase was strongly increased as a result of intraperitoneal injections of dextran solutions. Activity of acid phosphatase was determined with three substrates. The isoenzymes showed different conversion rates for the three substrates. The high molecular weight isoenzymes split the substrates 4-methylumbelliferyl phosphate, p-nitrophenyl phosphate and naphthol AS-BI phosphate. The activity was sensitive to the inhibitors fluoride and L(+)tartrate. In the pathologically altered liver tissue, which had stored dextran, the activity of these isoenzymes was strongly increased. The low molecular weight isoenzyme split 4-methylumbelliferyl phosphate and p-nitrophenyl phosphate but not naphthol AS-BI phosphate. Therefore this isoenzyme cannot be demonstrated with histochemical techniques using the substrate naphthol AS-BI phosphate. In contrast to the activity of the high molecular isoenzymes the activity of the low molecular isoenzyme was not changed in the pathologically altered liver tissue of mice and was not sensitive to the inhibitors fluoride and L(+)tartrate.This study was supported by a grant from the Prinses Beatrix Fonds, s'Gravenhage     

Dimeric nature and amino acid compositions of homogeneous canine prostatic human liver and rat liver acid phosphatase isoenzymes. Specificity and pH-dependence of the canine enzyme.

Two isoenzymes of rat liver acid phosphatase (orthophosphoric-monoester phosphohydrolase (acid optimum) EC 3.1.3.2) have been purified to homogeneity, at least one of these for the first time. Both of the rat liver isoenzymes have identical specific activities towards p-nitrophenyl phosphate. Molecular weights of the native enzymes are 92 000 for rat liver isoenzyme I and 93 000 for isoenzyme II, while the subunit molecular weights are 51 000 and 52 000 respectively. Data on substrate specificity and pH dependence are presented for the homogeneous canine prostatic enzyme, which is also isolated as a dimeric enzyme of (native) molecular weight 89 000. Carbohydrate analysis data are presented for canine prostatic acid phosphatase and it is further noted that both isoenzymes of rat liver acid phosphatase are also glycoproteins. The amino acid compositions of the two rat liver isoenzymes are presented together with those of the similar dimeric acid phosphatase of human liver and of canine prostate. Comparison of these results with published data for the amino acid composition of human prostatic acid phosphatase shows substantial similarities. However, significant differences are seen in the amino acid composition of rat liver acid phosphatase isoenzyme I as compared to a previous literature report. Most notably, 17 histidine residues are found per mol of isoenzyme I and 18 for isoenzyme II.     

Zymograms of Kurloff cell acid phosphatases. Thin layer isoelectric focusing and native polyacrylamide 4-15% gradient gel electrophoresis

Following previous light and ultrastructural cytochemical reports, this paper presents the first zymograms of Kurloff cell acid phosphatases extracted from highly purified cell suspensions. Using isoelectric focusing, up to 20 isoenzymes were observed both with hexazotised pararosanilin or fast garnet GBC as coupler and naphthol ASB1 phosphate as substrate. Most were tartrate-labile. After Clostridium-derived neuraminidase digestion, the highly stained bands observed at pH 4-5 disappeared and, simultaneously, a few alkaline bands were enhanced. Two main bands of Mr 190,000 and 500,000 were characterized by their acid phosphatase activity after electrophoresis on a 4-15% gradient native polyacrylamide gel.     

Integumental phosphatase isoenzymes from white puparia of Ceratitis capitata: isolation and characterization.

Two specific alkaline phosphatase forms were identified in the integument of wild-type Ceratitis capitata during transition of larvae to pupae. The separation was achieved by DEAE-cellulose chromatography; alkaline phosphatase 1 and alkaline phosphatase 2 were eluted in 0.1 and 0.4 M KCl, respectively. Both isoenzymes have a molecular weight of approximately 180,000. The pH curve reveals two peaks for both alkaline phosphatases: one at 9.4 and the other at 11.0. The two isoenzymes at both pH optima catalyze the hydrolysis of phosphotyrosine and beta-glycerophosphate, but not phosphoserine, phosphothreonine, ATP, or AMP. However, at pH 9.4, alkaline phosphatase 1 is more effective than ALPase 2 and exhibits a preference for phosphotyrosine. The divalent cations Mn2+, Mg2+, and Ba2+ activate the enzymes, while Cu2+ and Zn2+ are inhibitors for both isoenzymes. Both isoenzymes are inactivated by EDTA. The effect of amino acids on enzyme activity was also tested. Alkaline phosphatase 1 is inhibited by L-tyrosine, while alkaline phosphatase 2 is unaffected. L-Phenylalanine has no effect on either isoenzyme. Both isoenzymes are inhibited by urea and 2-mercaptoethanol. Simultaneous addition of urea and 2-mercaptoethanol reveals that ALPase 1 is more sensitive to these inhibitors than ALPase 2.     

Lysosomal hydrolase secretion by Tetrahymena: a comparison of several intralysosomal enzymes with the isoenzymes released into the medium.

Tetrahymena pyriformis were grown in proteose-peptone medium and then washed and incubated in a dilute salt solution for one hour. The cells were then discarded and the lysosomal hydrolases that had been secreted were subjected to DEAE cellulose column chromatography. At least three isoenzymes of acid phosphatase, three of acid protease, and two of beta-N-acetylhexoseaminidase were found, as well as single peaks of alpha-mannosidase, beta-galactosidase, and beta-fucosidase. The latter two activities were not resolved by the DEAE column and could not be separated in a second chromatographic step on CM-cellulose. Cells were also grown under identical conditions and homogenized in 0.25 M sucrose in order to allow comparison of some of the intracellular lysosomal hydrolases with their secreted counterparts. Two lysosomal populations were resolved by sucrose density gradient sedimentation, a heavy lysosomal fraction, contered at a density of about 1.25 gm/cm3, and a light lysosomal fraction, centered at a density of about 1.16 gm/cm3. These two populations differed in that the light lysosomes did not appear to contain significant amounts of beta-fucosidase, beta-galactosidase, or acid protease, whereas all six of the hydrolase activities studied were present in the heavy lysosomes. The light lysosomal peak occurred in cells grown to transition phase, but was markedly reduced in cells from cultures grown to stationary phase. In addition to these two fractions a third very light particle, containing only alpha-mannosidase activity, was detected just inside the gradient. Measurements were made of the effect of heat (10 minutes at 66 degrees) and of a change in pH from 4.5 (standard assay condition) to 6.0 on the three acid phosphatases and two beta-N-acetylhexoseaminidase isoenzymes resolved by DEAE column chromatography of the secreted hydrolases and on these hydrolyases in the heavy and light lysosomal fractions on the sucrose gradient. Use of the thermostability and pH criteria permitted computation of the expected properties of the intralysosomal acid phosphatase and hexoseaminidase activities if these consisted of the respective isoenzymes in the proportions secreted. It was found that neither the intralysosomal acid phosphatase nor the intralysosomal hexoseaminidase had the properties expected if they consisted of the secreted mixture of the respective isoenzymes, indicating that modification of some of these isoenzymes may have occurred during the 1-hour starvation period or after secretion.     

Purification and characterization of neuraminidase from Clostridium perfringens.

Clostridium perfringens cells were cultivated on a large scale using an automatic system. Neuraminidase secreted by the cells into the culture medium was purified 380 000-fold by: precipitation with ammonium sulfate between 50 and 85% saturation, filtration on Sephadex G-75, electrophoresis on polyacrylamide gel, and by isoelectric focusing. Three enzyme fractions with different migration rates were obtained by preparative disc electrophoresis in polyacrylamide gel, and five fractions with isoelectric points between pH 4.7 and 5.4 were observed after isoelectric focusing. This microheterogeneity disappeared after denaturation of the enzyme in 0.1% sodium dodecylsulfate or 8M urea. The isoelectric point of the denatured enzyme corresponded to pH 4.3. All enzyme fractions were identical with regard to their immunological and kinetic properties; they had the same molecular weights. The origin of the different "conformers" of neuraminidase is discussed. The existence of genuine isoenzymes could largely be excluded. The yield of neuraminidase was 65%, which corresponded to about 10 mg of pure enzyme from 100 l of culture medium. The enzyme was free of protease and various other glycosidase activities. The neuraminidase preparation appeared not to be contaminated by other proteins as judged by electrophoretic analysis using either the native enzyme or the enzyme denatured by sodium dodecylsulfate or urea; ultracentrifugation; chromatography on Sephadex G-200; and immunological methods. The molecular weights of the native or denatured enzyme were found to be in the range between 60 000 and 69 000 (on an average 63 750) using four independent methods. The existence of subunits of neuraminidase was excluded. The neuraminidase exhibited a spec. act. of 580 or 615 U/mg protein with glycopeptides from edible birds' nests or sialyllactose, respectively, as substrates. Additional kinetic properties and the UV-absorption spectrum of the enzyme are described.     

Cytochalasin B and the sialic acids of Ehrlich ascites cells

The effect of cytochalasin B (CB) on the electrophoretic mobility and density of ionized sialic acid groups at the surface of Ehrlich ascites cells was examined together with a biochemical assay of the total sialic acid content of treated and control cells. Sialic acid assays indicated that CB-treated cells had a greater amount of total sialic acid and sialic acid sensitive to neuraminidase than control cells/cell. Equal amounts of sialic acid were removable by neuraminidase treatment from control cells and cells pretreated with neuraminidase and subsequently cultured with CB. The electrophoresis results showed a decrease in electrophoretic mobility in the presence of CB which could be reversed by growth in CB-free medium. Neuraminidase treatment did not make a significant additional reduction in the mobility of CB-treated cells. CB also prevented the recovery of electrophoretic mobility of neuraminidase treated cells. The results suggest that while CB does not inhibit sialic acid synthesis, it does alter the expression of ionized sialic acid groups at the electrokinetic surface. CB-containing culture media could be re-utilized several times suggesting that CB is not significantly bound or metabolized by Ehrlich ascites cells.     

Characterization of human foetal intestinal alkaline phosphatase. Comparison with the isoenzymes from the adult intestine and human tumour cell lines.

The molecular structure of human foetal intestinal alkaline phosphatase was defined by high-resolution two-dimensional polyacrylamide-gel electrophoresis and amino acid inhibition studies. Comparison was made with the adult form of intestinal alkaline phosphatase, as well as with alkaline phosphatases isolated from cultured foetal amnion cells (FL) and a human tumour cell line (KB). Two non-identical subunits were isolated from the foetal intestinal isoenzyme, one having same molecular weight and isoelectric point as placental alkaline phosphatase, and the other corresponding to a glycosylated subunit of the adult intestinal enzyme. The FL-cell and KB-cell alkaline phosphatases were also found to contain two subunits similar to those of the foetal intestinal isoenzyme. Characterization of neuraminidase digests of the non-placental subunit showed it to be indistinguishable from the subunits of the adult intestinal isoenzyme. This implies that no new phosphatase structural gene is involved in the transition from the expression of foetal to adult intestinal alkaline phosphatase, but that the molecular changes involve suppression of the placental subunit and loss of neuraminic acid from the non-placental subunit. Enzyme-inhibition studies demonstrated an intermediate response to the inhibitors tested for the foetal intestinal, FL-cell and KB-cell isoenzymes when compared with the placental, adult intestinal and liver forms. This result is consistent with the mixed-subunit structure observed for the former set of isoenzymes. In summary, this study has defined the molecular subunit structure of the foetal intestinal form of alkaline phosphatase and has demonstrated its expression in a human tumour cell line.     

Isoproteins of human apolipoprotein A-II: isolation and characterization

In human serum, polymorphism of apoA-II predominantly in HDL3 could be demonstrated. HDL3-apoA-II was composed of four isoproteins, each with a molecular weight of 8600 (reduced form) and identical immunological properties. The isoproteins are designated apoA-II-1 (pI 5.16), apoA-II-2 (pI 4.89) corresponding to the already known apoA-II monomer band, apoA-II-3 (pI 4.58), and apoA-II-4 (pI 4.31). The amino acid compositions of the A-II isoproteins were virtually identical with the published data for apoA-II. Treatment with acid phosphatase, alkaline phosphatase, or neuraminidase before electrophoresis did not alter the apoA-II pattern. The apoA-II isoprotein pattern was studied in ten male and ten female normolipidemic volunteers, in two patients with Tangier disease, and in three patients with abetalipoproteinemia. The isoelectric focusing patterns of apoA-II appeared virtually identical in all subjects. However, in Tangier disease, due to the low apo-A-II concentration, only apoA-II-1 and apoA-II-2 were detectable, and in abetalipoproteinemia a different relative distribution pattern of the individual isoforms was found as compared to normal HDL3. Our studies indicate that apoA-II, similar to apoA-I, exists in several isoforms. The relationship of these isoforms to each other is at present unclear. They may originate from relatively basic isoproteins that are modified in charge by post-translational processes such as proteolytic cleavage, sequential deamidation, or other mechanisms.     

Physiochemical characterization of lymphocyte inhibitory factor (LyIF) isolated from avian B and T cells

Thymic (T) or bursal (B) lymphocytes from chicks sensitized to Mycobacterium tuberculosis produce an avian lymphocyte inhibitory factor (LyIF). The physiochemical properties of both T and B LyIF were established by ultrafiltration which yielded four fractions with molecular weight ranges of greater than 100,000; 50,000-100,000; 10,000-50,000; and less than 10,000; enzymatic treatment with chymotrypsin and neuraminidase; varying pH; and heat exposure. These studies demonstrated that the maximum activity for both T and B LyIF was within a molecular weight range of 10,000-50,000. Both were sensitive to chymotrypsin and neuraminidase treatment. Both were stable at 56 degrees C for 30 min and resistant to changes in pH from 5 to 9. T-Cell migration was inhibited equally by B or T LyIF, while B-cell migration was inhibited to a lesser extent by T LyIF and B LyIF. Further experiments should establish the reasons for these observed differences in cross-reactivity.     

The binding of cationized ferritin at the surfaces of ehrlich ascites tumor cells: the effect of pH and glutaraldehyde fixation.

The densities of cationized ferritin (CF) particles binding to the surfaces of cultured Ehrlich ascites tumor cells were determined at pH 7.4, where the ferritin stain was applied either prior to or following glutaraldehyde fixation. The densities were also determined with CF adjusted to pH 1.9 and applied after fixation. For all fixed samples there was a higher density of particles bound to microvilli than to the spaces between them. Treatment with neuraminidase removed more particles from microvilli than from the inter-microvillus spaces, but did not reduce the levels of binding to the same value. When cationized ferritin is applied prior to fixation, an aggregation of the CF particles at the cell surface was observed, with the internalization of some clusters. This effect was independent of neuraminidase treatment.     

Synthesis and use of an isoform-specific affinity matrix in the purification of glutathione S-transferases from the housefly, Musca domestica (L.)

Glutathione may be linked to an agarose matrix which has been activated by treatment with epichlorhydrin. The resulting resin displayed group selectivity for the glutathione S-transferases of the housefly Musca domestica (L). The isoenzymes of low isoelectric point, which have little activity with substrates other than 1-chloro-2,4-dinitrobenzene, bound strongly to this matrix and were eluted with 10 mM glutathione at pH 7.4. On the other hand, the group of isoenzymes of higher isoelectric point, showing activity with other substrates such as 3,4-dichloronitrobenzene, did not bind. These isoenzymes did bind to a sulfobromophthalein-glutathione conjugate immobilized on agarose and could be eluted with 5 mM sulfobromophthalein at pH 7.4. The immobilized glutathione resin bound rat liver glutathione S-transferase subunits from all three molecular weight classes.     

Enzymatic properties of neuraminidases from Arthrobacter ureafaciens.

Neuraminidase I and neuraminidase II from Arthrobacter ureafaciens were characterized. As determined by gel filtration on Ultrogel AcA 44, the molecular weights of neuraminidases I and II were 51,000 and 39,000, respectively. Neuraminidases I and II were similar to each other in their enzymatic properties except for the substrate specificities towards gangliosides and erythrocyte stroma. Their optimal pHs were between 5.0 and 5.5 with N-acetylneuraminosyl-lactose or bovine submaxillary mucin as substrates, but with colominic acid as a substrate, the pH optimum was between 4.3 and 4.5. They were most active around 53 degrees C, were stable between pH 6.0 and 9.0, and were thermostable up to 50 degrees C. They did not require Ca2+ for activity and were not inhibited by EDTA. They were inhibited only slightly or not at all by p-chloromercuribenzoic acid of Hg2+. Both neuraminidases I and II were able to hydrolyze the alpha-ketosidic linkage of N-glycolylneuraminic acid as well as that of N-acetylneuraminic acid, and were able to liberate substantially all of the sialic acid from various kinds of substrates. However, they cleaved only about 50% of the sialic acid from bovine submaxillary mucin. The saponification of bovine submaxillary mucin by mild alkali treatment, on the other hand, resulted in an increased susceptibility to the neuraminidases and brought about the complete liberation of sialic acid. Remarkable differences were observed between neuraminidases I and II as regards substrate specificities on gangliosides; the initial rate of hydrolysis by neuraminidase I was 74 times, and its maximum velocity constant was 91 times those of neuraminidase II. The addition of sodium cholate markedly stimulated the enzymatic hydrolysis of gangliosides, and increased the maximum velocity constant of neuraminidase I twofold and that of neuraminidase II 143-fold. Although neuraminidases I and II were able to hydrolyze (alpha,2-3), (alpha,2-6), and (alpha,2-8) linkages, the initial rate of hydrolysis of N-acetylneuraminosyl-alpha,2-6-lactose was greater than that of the alpha,2-3-isomer.     

Metabolic relationship between invertase and acid phosphatase isoenzymes in Saccharomyces cerevisiae

Repressed cells of Saccharomyces cerevisiae, subjected to inhibition of both RNA and protein synthesis, showed a pattern of membrane-bound and cytosol acid phosphatase to the external enzyme which seemed to be linked through a precursor-product relationship.Gel exclusion chromatography did not indicate clear differences between the isoenzymes. Moreover, centrifugation experiments in CsCl and precipitation with concanavalin A suggested that there were no acid phosphatase molecules devoid of carbohydrate. Membrane-bound invertase displayed a molecular weight and a carbohydrate to protein ratio smaller than those of the exocellular enzyme. The values of molecular weight and buoyant density of the membrane-bound enzyme were closer to those found for the cytosol invertase. The stability of the level of the soluble invertase detected in the cytoplasm under derepression conditions, or after RNA or protein synthesis inhibition was found to be only apparent and represented the result of an equilibrium between synthesis and degradation.     

Acetylesterase isoenzymes in rat uterus and placenta

The occurrence of acetylesterase activity in the uterus and placenta of the rat has been investigated using a general histochemical simultaneous coupling technique after separation on polyacrylamide gradient gels. apart from a complex band associated with serum esterases which was demonstrated in all the tissues studied, several other isoenzyme bands were demonstrable in differing degrees in the yolk sac and the virgin uterus. Two of these bands were evident in metrial gland up to day 16 of pregnancy, and a third became present by day 17. Unlike the other two bands, this new band did not seem to be associated with the large granules of the granulated metrial gland cells. None of these bands were detected in trophoblast. The metrial gland isoenzymes reacted as well at acid pH as at neutral pH. The yolk sac isoenzymes reacted either as well or slightly better at acid pH, and one extra band was demonstrable under acid conditions.     

Histochemical analysis of molluscan stomach and intestinal alkaline phosphatase: A sialoglycoprotein

Summary Though sialoprotein nature of alkaline phosphatase of certain mammalian organs has been suggested by biochemical investigations, no histochemical techniques have yet been applied to elucidate this concept. With this view, the alkaline phosphatase of stomach and intestine of a mollusc—Semperula maculata—was analysed histochemically to elucidate its sialoglycoprotein nature. The localisation of alkaline phosphatase and sialic acid was investigated by employing well known and standard histochemical techniques.Alkaline phosphatase was localised selectively in the brush border of the mucosa of stomach and intestine, it was Mg⁺⁺ nonsensitive but showed a structure-linked sensitivity to phenylalanine. The sialomucins were selectively localised in the brush border, whereas the goblet cells contained both the sialomucins and sulfomucins, and the connective tissue of lamina propria contained sulfomucins. The localisation of alkaline phosphatase and sialomucins in the brush border uniquely coincided with each other. The alkaline phosphatase activity in the brush border was completely lost after neuraminidase treatment at 37.5° C for 16 h. Such effect of neuraminidase on alkaline phosphatase activity was pH dependent and controlled by velocity of reaction. Heat-inactivated neuraminidase showed no effect on alkaline phosphatase activity.These histochemical results have been interpreted as suggesting a sialoglycoprotein nature of alkaline phosphatase in the brush border, and sialic acid somehow seems to be essential for enzyme activity. These results, thus, indicate necessity of visualising some of the sialo-glycoproteins as macromolecules with catalytic activity.     

Synthesis and use of an isoform-specific affinity matrix in the purification of glutathione S-transferases from the housefly, Musca domestica (L.)

Glutathione may be linked to an agarose matrix which has been activated by treatment with epichlorhydrin. The resulting resin displayed group selectivity for the glutathione S-transferases of the housefly Musca domestics (L). The isoenzymes of low isoelectric point, which have little activity with substrates other than 1-chloro-2,4-dinitrobenzene, bound strongly to this matrix and were eluted with 10 mm glutathione at pH 7.4. On the other hand, the group of isoenzymes of higher isoelectric point, showing activity with other substrates such as 3,4-dichloronitrobenzene, did not bind. These isoenzymes did bind to a sulfobromophthalein-glutathione conjugate immobilized on agarose and could be eluted with 5 mm sulfobromophthalein at pH 7.4. The immobilized glutathione resin bound rat liver glutathione S-transferase subunits from all three molecular weight classes.