Interaction of radical anion probes with glucoamylase I from Aspergillus niger

The radical anions (SCN)2.- and Br2.- produced during a pulse radiolysis of the respective potassium salts have been used to study the tryptophan residues of the glucoenzyme, glucoamylase I (EC 3.2.1.3.). At neutral pH, Br2.- reacted with the tryptophan residues of glucoamylase I as expected from previous studies of proteins and free amino acids. However, (SCN)2.- at neutral and high pH was surprisingly unreactive towards the native enzyme. Reaction did occur, however, between (SCN)2.- and glucoamylase from which one-third of the covalently bound carbohydrate had been removed, producing a tryptophyl radical. Reaction also occured between (SCN)2.- and glucoamylase I inactivated by treatment with sodium dodecyl sulphate, but the tryptophan residues were not involved. It is concluded from the results that two 'types' of tryptophan residues are found in glucoamylase I; both are attacked by Br2.- but only one type is attacked by (SCN)2.-.

Amino acid sequence at the active site of beta-glucosidase A from bitter almonds

beta-Glucosidase A from bitter almonds was inhibited by the substrate analogue 6-bromo-3,4,5-trihydroxycyclo[2-3H]hex-1-ene oxide. Incorporation of 2 mol inhibitor/mol of dimeric enzyme resulted in total loss of activity. From tryptic digests of the labeled enzyme two radioactive peptides were isolated and their sequence determined (binding site of inhibitor underlined): peptide I, containing approx. 60% of the label: Ile-Thr-Glx-Glx-Gly-Val--Phe-Gly-Asp-Ser-Glx-(Ala, Asx2, Pro)-Lys and peptide II with approx. 30% of the label: Gly-Thr-Glx-Asp. The specifity of the reaction of beta-glucosidases (beta-D-glucoside glucohydrolase, EC 3.2.1.21) with substrate-related epoxides indicates that the aspartic acid labeled in peptide I participates in the catalytic process of beta-glucoside hydrolysis. The labeling of a second site is interpreted in terms of two, mutually exclusive, binding modes of the inhibitor.

Rapid and sensitive, colorimetric determination of the anomers of D-glucose with D-glucose oxidase, peroxidase, and mutarotase

A modification, utilising mutarotase, of an enzymic, colorimetric system for determining D-glucose with D-glucose oxidase, peroxidase, and ABTS was satisfactory for the assay of the anomers of D-glucose in aqueous solution. The time required for a single assay is approximately 10 min, and the lower limit is 0.4 microgram of D-glucose. The method is applicable to the anomer analysis of D-glucose released by enzymic hydrolysis of D-glucosides.

The apparent molecular weights of human intestinal aminopeptidase, enterokinase and maltase in native duodenal fluid

The apparent molecular weights of human intestinal aminopeptidase, enterokinase and maltase in native duodenal fluid were estimated by gel chromatography on Sephadex G-200 under different conditions of operational buffer and temperature. No evidence for environmentally induced changes in molecular form was found.

The enzymic degradation of an alkali-soluble glucan from the cell walls of Saccharomyces cerevisiae

An alkali-soluble glucan from the cell walls of Saccharomyces cerevisiae NCYC1109 has been hydrolysed with a purified endo-(1 leads to 3)-beta-D-glucanase and an endo-(1 leads to 6)-beta-D-glucanase from Bacillus circulans WL-12. The products of enzyme action include various oligosaccharide and polysaccharide fractions which have been separated by gel filtration and characterized, giving new information on the fine structure of the glucan. The isolated cell walls have also been subjected to enzymic hydrolysis. The results suggest that part of the cell-wall mannan is held in place by a glucan component.

Immobilization of enzymes based on hydrophobic interaction. II. Preparation and properties of an amyloglucosidase adsorbate

Amyloglucosidase from Aspergillus niger (alpha-1,4 and 1,6 glucan glucohydrolase, EC 3.2.1.3) was immobilized through adsorption onto a hexyl-Sepharose, containing 0.51 mol hexyl-group per mole of galactose. The adsporption limit of the carrier with respect to this enzyme was about 17 mg per gram wet conjugate. The retention of activity upon immobilization was high, varying from essentially full activity at low enzyme content down to 68% at the adsorption limit. The immobilized preparation, as well as the soluble enzyme, showed apparent zero order kinetics within 60% of the substrate's conversion limit. Product inhibition of the soluble enzyme showed a KI of 5-10(-2)M. In the presence of 3M NaCl, adsorbates were formed more rapidly and with a higher yield of immobilized protein, but with lower specific activity. Conjugates resulting from adsorption of amyloglucosidase in identical concentrations, but at different salt contents, showed comparable activities and operational stabilities. Continuous operation from three months reduced conjugate activity to 40%. The thermal stability of the adsorbate was inferior to that of the soluble enzyme, but was noticeably enhanced in the presence of substrate.

Enzymatic, fluorometric assay of alpha-amylase in serum

An enzymatic, fluorometric method for kinetic assay of serum alpha-amylase (1,4alpha-D-glucan 4-glucanohydrolase, EC 3.2.1.1) is described. A soluble starch is used as substrate, in tris(hydroxymethyl)methylamine buffer. All measurements are made in Pyrex cuvettes at 37 degrees C, with a reaction volume of 1.16 ml. The assay is based on the following reaction sequence: (see article) The rate of appearance of fluorescence of NADH (lambdaex = 365 nm, lambdaem = 460 nm), developed in the indicator reaction (4), is measured and equated to the activity of alpha-amylase in serum. A calibration plot of the change of fluorescence per min vs. enzyme concentration shows a good proportionality in the range of 0.50-5.0 kU/liter.

Immunochemical analysis of an unusual cell wall polysaccharide from animal coagulase-positive staphylococci. 1. Fragments obtained after hydrolysis in hydrofluoric acid and alkali

Polysaccharide P (poly P) of canine coagulase-positive staphylococci contains glycerol, glucose, glucosamine, muramic acid, phosphate, and the usual peptidoglycan amino acids, but does not cross-react serologically with standard teichoic acids. Products from hydrolyses in hydrofluoric acid and alkali contained phosphates of glycerol and glucose as well as combinations of these, but neither glucosyl-glycerol units nor glucosamine-phosphates were observed. The teichoic acid of poly P is probably a polymer of a repeating unit consisting of alternating glycerol, phosphate and glucose.

Enzyme immunoassay of testosterone using the testosterone-glucoamylase complex

A highly sensitive, reproducible method was established for enzyme-coupled immunoassay of testosterone, involving coupling of testosterone to glucoamylase [EC 3.2.1.3] with a water-soluble coupling reagen carbodimide. No enzyme activity was lost during this coupling procedure. The sensitivity of the method was comparable to that of competitive protein binding assay.

Transport of maltose by Pseudomonas fluorescens W

The system for uptake of maltose in Pseudomonas fluorescens W was inducible. Using a mutant strain unable to hydrolyze maltose, it was shown that maltose was taken up unaltered against a concentration gradient. Uptake of 14C maltose was only significantly inhibited by nonradioactive maltose or maltotriose. These were the only sugars that could displace accumulated radioactive maltose in the strain unable to hydrolyze maltose. Uptake exhibited saturation kinetics and was inhibited by energy poisons, indicating that this system was one of active transport. Sulfhydryl-binding reagents reversibly inhibited maltose uptake. No transport ability was lost when cells were subjected to osmotic shock. Using the protein-binding dye 7-diazonium-1, 3-naphthalene disulfonate a protein or proteins located in or external to the cell membrane was implicated in maltose transport. The hydrolysis of p-nitrophenyl-alpha-D-glucoside (PNPG) was used as an indirect measure of transport ability since penetration of PNPG, not its hydrolysis, was the rate-limiting step.

The structure of teichoic acid from Bacillus subtilis var, niger WM as determined by C nuclear-magnetic-resonance spectroscopy

The walls of Bacillus subtilis var. niger WM, grown in a Mg2+ -limited chemostat culture (carbon source glucose, dilution rate = 0.2 h(-1), 37 degrees C, pH 7) contained 45% (w/w) teichoic acid, a polymer composed of glycerol, phosphate[ and glucose in the molar ratio 1.00:1.00:0.88, respectively. Alkaline hydrolysis of this teichoic acid yeilded 1-O-beta-glucosylglycerol phosphate (together with small amounts of glycerol phosphate0 and 13C nuclear magnetic resonance spectra of this hydrolysis product, and its derivative after alkaline phosphate treatment, confirmed that the monomeric unit was 1-O-beta-glucosylglycerol-3-phosphate. Assignment of the resonances in the spectrum of undergraded teichoic acid revealed that the polymer was a poly [(2,3) glycerol phosphate 1, glucosidically substituted on C-1 of glycerol with beta-glucose.

Studies on the cell wall of Schizophyllum commune. Permethylation and enzymic hydrolysis

Two polysaccharide fractions S-glucan were isolated from the cell walls of Schizophyllumcommune. S-Glucan is primarily a linear 1,3-alpha-glucan with occasional 1,6-alphalinkages as shown by permethylation and partial acid hydrolysis. The glucan fraction also contains a small amount of xylose. The R-glucan fraction is a mixture of two polysaccharides, chitin and a highly branched glucan with linear 1,6-beta and 1,3-beta segments and 1,6-beta branching. This conclusion is based on permethylation studies and enzymic hydrolyses.

Variation in average unit chain length of glycogen in relation to developmental stage in Blastocladiella emersonii

Synchronous, single generations of Blastocladiella emersonii were grown along either the ordinary colorless or resistant sporangial plant pathways. Samples of cells were withdrawn at different developmental stages and glycogen was extracted, purified, debranched by isoamylase treatment, and its component unit chains separated by gel permeation chromatography. The elution profiles showed the distribution of unit chains. Average unit chain length was determined for plants at different developmental stages and shown to vary between 9 and 16. Some of these variations were correlated with other developmental events in the fungus.

Magnetic enzyme membranes as active elements of electrochemical sensors. Lactose, saccharose, maltose bienzyme electrodes

The direct monitoring of sugars such as lactose, maltose, saccharose is not only useful at the applied point of view but also at the fundamental point of view for studying enzymology, especially in microbiology and fermentation. Benzyme systems were extensively used in solution for analytical applications in industry and medicine. The progress in the field of immobilization of bienzyme systems [1-3], especially within membranes [4-5], makes possible the production of new analytical devices. From the studies dealing with concentration profiles in artificial enzyme membranes [14], evidence was obtained for a well defined relationship between the local concentration of a metabolite and concentration of the first substrate in the bulk solution. In the described systems a substrate is transformed into glucose within a membrane, the glucose is then transformed in gluconic acid with a local oxygen consumption. The local pO2 level is linked to the glucose oxidase velocity, which is only linked to the glucose production, that is to say to the concentration of the first substrate. The enzyme electrode is based on the transformation of kinetic phenomena (reaction rates) into absolute values (local concentrations) through the diffusion-reaction coupling process. The manufacture of magnetic enzyme electrodes [6] allows convenient use of the active sensors. The pO2 electrode has some adventages, namely the specificity based on the selectivity of the gas permeable membrane and the linear relationship between the oxygen and the output of the electrode. pCO2, pH, ion electrodes give a logarithmic response as a function of the concentration. The grafting of a multienzyme system on a sensor allows a study of sequential systems in a defined context with a measurement of the local concentration of the metabolites. The tool is useful for both kinetics [4] and regulation studies [5].