Mannosidase, glucosidase, and galactosidase in sweet almond emulsin

Effect of almond processing on levels and distribution of aflatoxins in finished products and byproducts

The fate of aflatoxins during processing of contaminated almonds into nougat, pastries, and almond syrup was evaluated by testing the effect of each processing step (blanching, peeling, roasting, caramelization, cooking, and water infusion) on the distribution and levels of aflatoxins. Blanching and peeling did not reduce total aflatoxins that were distributed between peeled almonds (90-93%) and skins (7-10%). Roasting of peeled almonds reduced up to 50% of aflatoxins. Up to 70% reduction of aflatoxins was observed during preparation and cooking of almond nougat in caramelized sugar. Aflatoxins were substantially stable during preparation and cooking of almond pastries. The whole process of almond syrup preparation produced a marked increase of total aflatoxins (up to 270%) that were distributed between syrup (18-25%) and spent almonds (75-82%). The increase of total aflatoxins was probably due to the activation of almond enzymes during the infusion step that released free aflatoxins from masked aflatoxins.

Monitoring carbohydrate enzymatic reactions by quantitative in vitro microdialysis

On-line in vitro microdialysis (MD) sampling followed by HPLC separation and UV absorbance detection (HPLC-UV) was used to monitor carbohydrate enzyme systems. Fundamental parameters (i.e., K(m) and V(max)) of hydrolysis reactions of 4-nitrophenyl-beta-D-glucopyranoside, 4-nitrophenyl-beta-d-galactopyranoside, and 4-nitrophenyl-beta-D-xylopyranoside were determined for a model enzyme, almond beta-glucosidase. Accurate quantitation was achieved via internal standard methodology and compared to spectrophotometric data and literature K(m) values, which were found to be 2.6+/-0.5 mM (MD), 2.7+/-0.4 mM (spec), and 2.5 mM (lit), for the substrate 4-nitrophenyl-beta-d-glucopyranoside. A previously unpublished K(m) value for the substrate salicin was also determined by this method. An application is shown for monitoring the glycoside salicin and its hydrolysis product saligenin in a commercially available willow bark product that is used for making tea. This versatile method has far-reaching applications to monitoring a variety of carbohydrates in enzymatic processes without complex sample preparation procedures and without volume loss.

Three Distinct Read-Out Modes for Enzyme Activity Can Operate in a Semi-Wet Supramolecular Hydrogel

Assays of hydrolytic enzyme activity, such as of glycosidases and phosphatase, as well as several proteases, using a semi-wet supramolecular hydrogel array composed of a glycosylated amino acetate are described. It has been demonstrated that the microcavity formed by gel fibrils is suitable to immobilize native enzymes without denaturation under semi-wet conditions, and thus the nanofiber has been rationally used as a sensing domain to monitor enzymatic reactions. By using a fluorogenic substrate, reducing the size of the hydrogel can significantly improve the problem of suppressed diffusion within the gel matrix thus making the hydrogel a promising semi-wet matrix for evaluating enzyme activity. Confocal laser scanning microscopy observations have shown that an environmentally sensitive fluorescent probe accumulates in the hydrophobic domain of the gel fiber and emits fluorescence more strongly upon hydrolytic cleavage of the substrate peptides. Not only a simple environmentally sensitive probe but also a FRET (fluorescence resonance energy transfer)-type read-out mode can be devised to analyze the enzymatic hydrolysis-triggered redistribution of the probe between the nanospace and the nanofiber to accomplish a more clearly distinguished enzyme assay. Thus, it is clear that three distinct read-out modes, that is, 1) fluorogenic substrates, 2) substrates bearing an environmentally sensitive probe, or 3) a substrate exhibiting FRET, can operate under the semi-wet hydrogel conditions used in these investigations. In addition, owing to the unique properties of the present supramolecular hydrogel in semi-wet conditions, that is, its phase-segregation properties and dynamics, the supramolecular substrate/enzyme array has successfully been used for high-throughput screening of single and multiple enzymes based on their activity, lysate analysis, and quantitative evaluation of inhibitor potency and selectivity.

Characterization of almond α-mannosidase and its application for structure analysis of sugar chain

Almond alpha-mannosidase was purified by separation on columns of DEAE-Sephadex A50 and hydroxyapatite, and characterized. Its optimum pH was approximately 3.8. It was also shown to be stable from pH 6 to 8. Its activity was stable up to 60 degrees C. The thermostability of almond alpha-mannosidase at 73 degrees C appeared to be superior to that of jack bean a-mannosidase. We examined the substrate specificity of the former toward high-mannose-type N-glycan Man9GlcNAc2, and showed that the deduced trimming pathway was more diverse than that of the latter. We could use almond alpha-mannosidase as well as jack bean alpha-mannosidase for analysis of sugar chain structures.

Selenium-mediated differential response of beta-glucosidase and beta-galactosidase of germinating Trigonella foenum-graecum

Beta-glucosidase and beta-galactosidase activity profile tested in different seeds during 24 h germination revealed reasonably high levels of activity in Vigna radiata, Cicer arietinum, and Trigonella foenum-graecum. In all seeds tested, beta-galactosidase activity was, in general, higher than that of beta-glucosidase. T. foenum-graecum seedlings exhibited maximal total and specific activities for both the enzymes during 72 h germination. Se supplementation as Na2SeO3 up to 0.75 ppm was found to be beneficial to growth and revealed selective enhancement of beta-galactosidase activity by 40% at 0.5 ppm Se. The activities of both the enzymes drastically decreased at 1.0 ppm level of Se supplementation. On the contrary, addition of Na2SeO3 in vitro up to 1 ppm to the enzyme extracts did not influence these activities. Hydrolytic rates of beta-glucosidase in both control and Se-supplemented groups were enhanced by 20% with 0.05 M glycerol in the medium and 30% at 0.1 M glycerol. The rates were marginally higher in Se-supplemented seedlings than the controls, irrespective of added glycerol in the medium. In contrast, hydrolysis by beta-galactosidase showed a trend of decrease in Se-supplemented seedlings compared to the control, when glycerol was present in the medium. Addition of Se in vitro in the assay medium showed no difference in the hydrolytic rate by beta-galactosidase when compared to control, while the activity of beta-glucosidase declined by 50%. Se-grown seedlings showed an enhancement of transglucosidation rate by 40% in the presence of 0.1 M glycerol. The study reveals a differential response to Se among the beta-galactosidase and beta-glucosidase of T. foenum-graecum with increase in the levels of beta-galactosidase activity.

The alpha-mannosidase from Canavalia ensiformis seeds: chemical and kinetic properties and action on animal lymphocytes

The alpha-mannosidase from Canavalia ensiformis was characterized with respect to molecular mass, glycoprotein nature, amino-acid composition, enzymic properties and action on animal cells. The enzyme is composed of two pairs of subunits (molecular mass 44 and 66 kDa) which form a tetramer (220 kDa). The larger subunit is glycosylated, the smaller one is not. Both subunits have similar amino-acid compositions. The larger subunit contains a surplus of alanine, aspartic acid/asparagine, histidine, phenylalanine and tyrosine, the smaller one a surplus of glutamic acid/glutamine, serine and threonine. The enzyme is subject to product inhibition by mannose. It stimulates the proliferation of B-lymphocytes from nude mice.

A stepwise approach to the understanding of extracellular enzyme activity in soil. I. Effect of electrostatic interactions on the conformation of a beta-D-glucosidase adsorbed on different mineral surfaces

The enzymatic activity of sweet almond beta-D-glucosidase adsorbed on various mineral surfaces was studied. Our aim was to elucidate the mechanism responsible for the observed changes in catalytic activity. The results of the investigation are discussed with reference to the hypotheses generally proposed to explain the well-documented shift in optimal pH of the activity of adsorbed enzymes. By separate determinations of enzymatic activity in a mineral suspension and of its supernatant solution, and comparison with a control without mineral added, we obtained accurate measurements of the catalytic activity of the adsorbed enzyme alone. Different pH profiles of activity profiles were found when the enzyme was adsorbed onto montmorillonite, kaolinite and goethite. The activity profiles, were also found to vary with ionic strength, the pH at which enzyme adsorbed onto the mineral surface, and in the case of goethite, on the nature of the anions in the buffer. Our observations cannot be adequately explained by assuming a more acidic microenvironment at the mineral surface. We postulate that on some mineral surfaces a conformational change is induced in the adsorbed protein, which reduces its catalytic activity. We contend that such conformational changes are due primarily to electrostatic forces.

Strong inhibitory effect of furanoses and sugar lactones on beta-galactosidase Escherichia coli

Various sugars and their lactones were tested for their inhibition of beta-galactosidase (Escherichia coli). L-Ribose, which in the furanose form has a hydroxyl configuration similar to that of D-galactose at positions equivalent to the 3- and 4-positions of D-galactose, was a very strong inhibitor, and D-lyxose, which in the furanose form also resembles D-galactose, was a much better inhibitor than expected. Structural comparisons prelude the pyranose forms of these sugars from being significant contributors to the inhibition, and inhibition at different temperatures (at which there are different furanose concentrations) strongly supported the conclusion that the furanose form is inhibitory. Studies with sugar derivatives that can only be in the furanose form also supported the conclusion. This is the first report of the inhibitory effect of furanose on beta-galactosidase. Lactones were also inhibitory. Every lactone tested was much more inhibitory than was its parent sugar. D-Galactonolactone was especially good. Experiments indicated that it was D-galactono-1,5-lactone rather than D-galactono-1,4-lactone which was inhibitory. Inhibition of beta-galactosidases from mammalian sources by lactones has been reported previously, but this is the first report of the effect of beta-galactosidase from E. coli. Since furanoses in the envelope form are analogous (in some ways) to half-chair or sofa conformations and since lactones with six-membered rings probably have half-chair or sofa conformations, the results indicate that beta-galactosidase probably destabilizes its substrate into a planar conformation of some type and that the galactose in the transition state may, therefore, also be quite planar.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth of toxic-shock-syndrome strain of Staphylococcus aureus after enzymic degradation of 'Rely' tampon component

beta-glucosidase, cellulase, alpha-mannosidase, beta-galactosidase, and N-acetyl-beta-glucosaminidase were tested for their ability to hydrolyse the carboxymethylcellulose contained in 'Rely' tampons (R-CMC). The end-products of the hydrolysis were determined by chromatography. Only beta-glucosidase and cellulase hydrolysed R-CMC and the major product detectable after enzymic degradation was glucose, as confirmed chromatographically and by the glucose oxidase test. The enzymic-degradation products of R-CMC were able to support the growth of a toxic-shock-syndrome strain of Staphylococcus aureus. This finding suggests that as it is degraded by enzymes in the vaginal cavity R-CMC may become an exogenous source of nutrients for pathogenic organisms.

beta-D-Mannosidase from Helix pomatia

beta-D-Mannosidase (beta-D-mannoside mannohydrolase EC 3.2.1.25) was purified 160-fold from crude gut-solution of Helix pomatia by three chromatographic steps and then gave a single protein band (mol. wt. 94,000) on SDS-gel electrophoresis, and three protein bands (of almost identical isoelectric points) on thin-layer isoelectric focusing. Each of these protein bands had enzyme activity. The specific activity of the purified enzyme on p-nitrophenyl beta-D-mannopyranoside was 1694 nkat/mg at 40 degrees and it was devoid of alpha-D-mannosidase, beta-D-galactosidase, 2-acetamido-2-deoxy-D-glucosidase, (1 leads to 4)-beta-D-mannanase, and (1 leads to 4)-beta-D-glucanase activities, almost devoid of alpha-D-galactosidase activity, and contaminated with less than 0.02% of beta-D-glucosidase activity. The purified enzyme had the same Km for borohydride-reduced beta-D-manno-oligosaccharides of d.p. 3-5 (12.5mM). The initial rate of hydrolysis of (1 leads to 4)-linked beta-D-manno-oligosaccharides of d.p. 2-5 and of reduced beta-D-manno-oligosaccharides of d.p. 3-5 was the same, and o-nitrophenyl, methylumbelliferyl, and naphthyl beta-D-mannopyranosides were readily hydrolysed. beta-D-Mannobiose was hydrolysed at a rate approximately 25 times that of 6(1)-alpha-D-galactosyl-beta-D-mannobiose and 6(3)-alpha-D-galactosyl-beta-D-mannotetraose, and at approximately 90 times the rate for beta-D-mannobi-itol.

Enzymatic modification of bacterial receptors on saliva-treated hydroxyapatite surfaces

Certain properties of experimental pellicles formed by the adsorption of salivary components on hydroxyapatite surfaces change over time. To determine whether enzymes likely to be present in the oral environment could induce such changes, pellicles were treated with saliva which had been incubated for 18 h at 35 degrees C to promote the elaboration of microbial enzymes. This treatment markedly reduced the numbers of Streptococcus mutans MT3 and JBP and S. sanguis FC-1 and C5 cells which attached, but it had little or no effect on the attachment of S. mitis RE7, Actinomyces viscosus LY7 and CK-8, Bacteroides gingivalis 381, or B. melaninogenicus subsp. intermedius 581. Heating the incubated saliva at 60 degrees C for 30 min partially reduced its pellicle-modifying activity, whereas heating at 80 degrees C for 30 min or 100 degrees C for 15 min completely eliminated such activity. This indicated that the saliva contained heat-labile substances, presumably enzymes, which could affect the pellicle receptors involved in the attachment of S. mutans and S. sanguis. Treatment of saliva-treated hydroxyapatite with commercially obtained enzyme preparations also affected bacterial attachment. Thus, treatment with galactose oxidase reduced the numbers of the S. mutans strains which attached, whereas treatment with neuraminidase reduced the adsorption of S. sanguis FC-1 but not that of S. sanguis C5. Treatment with beta-glucosidase preparations derived from almonds significantly reduced the attachment of all of the streptococcal strains studied, but, when subjected to isoelectric fractionation, the adherence-inhibiting activity did not correlate directly with beta-glucosidase activity. Treatment of the pellicles with trypsin or eight other glycosidases did not affect streptococcal attachment. Exposure of the enzymatically modified pellicles to fresh saliva did not restore the streptococcal receptors. Collectively, the data suggest that some bacterial receptors in the pellicle coating of teeth can be modified by enzymes likely to be present in the oral environment, and these interactions may affect oral bacterial ecology.

Either high-mannose-type or hybrid-type oligosaccharide is linked to the same asparagine residue in ovalbumin

After pepsin digestion, all of the carbohydrates in ovalbumin were recovered in two glycopeptides, Glu-Glu-Lys-Tyr-Asn(CHO)-Leu-Thr-Ser-Val and Glu-Gln-Lys-Tyr-Asn(CHO)-Leu-Thr-Ser-Val. Almond glycopeptidase released quantitatively oligosaccharides from the glycopeptides. The products from both glycopeptides contained both the high-mannose-type oligosaccharides and the hybrid-type oligosaccharides in the same ratio. Thus, either the high-mannose-type or the hybrid-type oligosaccharide is attached to the unique asparagine residue in the ovalbumin molecule.