Imaging β-galactosidase activity using 19F chemical shift imaging of LacZ gene-reporter molecule 2-fluoro-4-nitrophenol-β-d-galactopyranoside

2-Fluoro-4-nitrophenol-beta-D-galactopyranoside (OFPNPG) belongs to a novel class of NMR active molecules (fluoroaryl-beta-D-galactopyranosides), which are highly responsive to the action of beta-galactosidase (beta-gal). OFPNPG has a single 19F peak (-55 ppm relative to aqueous sodium trifluoroacetate). Upon cleavage by beta-gal, the pH sensitive aglycone 2-fluoro-4-nitrophenol (OFPNP) is observed at a chemical shift of -59 to -61 ppm. The chemical shift response is sufficient to observe beta-gal activity using chemical shift imaging (CSI). 19F CSI studies of enzyme activity and lacZ gene expression in 9L-glioma and MCF7 breast cancer cells are presented, providing further evidence for the utility of OFPNPG as a gene-reporter molecule for future in vivo studies.

Preparation and properties of alpha-galactosidase chemically attached to activated chitin

alpha-Galactosidase (alpha-D-galactoside galactohydrolase, EC 3.2.1.22) from watermelon was covalently immobilized on chitin. The immobilized alpha-galactosidase exhibited an activity of 0.61 U per g of carrier and an activity yield of 67%. The properties of free and immobilized alpha-galactosidase were also searched and compared. The results showed that, optimum conditions for activity were not affected by immobilization. The optimum pH and temperature for free and immobilized enzyme found as pH 6.0 and 65 degress C, respectively. Compared with the free enzyme, the temperature and pH stabilities of the immobilized enzyme were similar. Both the enzymes were stable between pH 2-10 and below 50 degrees C. The Km values for free and immobilized enzyme were determined using p-nitrophenyl-alpha-D-galactopyranoside (PNPG) and raffinose as substrates. Operational stability of the immobilized enzyme was investigated by using both substrates. The operational half-life (t 1/2) was calculated as 34 h for PNPG and 28 h for raffinose. The immobilized alpha-galactosidase was also utilized in the hydrolysis of raffinose. The immobilization procedure on chitin was cheap and also easy to carry out, and the immobilized enzyme had good properties that the potential for practical application is considerable.

Hepatitis C virus E1 protein induces modification of membrane permeability in E. coli cells

The E1 gene of hepatitis C virus (HCV) has been cloned and expressed in BL21(DE3)pLys Escherichia coli strain by pET3a vector to analyze changes in membrane permeability produced by this protein. We showed that the expression of E1 (aa 192-383), as well as of two C-terminal fragments (aa 331-383 and aa 341-383) corresponding to the transmembrane (TM) region of this protein, induced a rapid lysis of cells. On the contrary, the expression of a mutant of E1 (aa 192-340), lacking the last 40 amino acids, did not cause cell lysis. The analysis of permeability changes revealed that modification of membrane permeability to several compounds were observed only in clones expressing E1 and C-terminal fragments, while the synthesis of the C-terminal-deleted mutant had little or no effect on permeability. These findings demonstrate that the TM domain of E1 protein has membrane-active properties that may be involved in some aspects of virus-cell interaction.

Substrate-directed formation of small biocatalysts under prebiotic conditions

One of the most debated issues concerning the origin of life, is how enzymes which are essential for existence of any living organism, evolved. It is clear that, regardless of the exact mechanism, the process should have been specific and reproducible, involving interactions between different molecules. We propose that substrate templating played a crucial role in maintaining reproducible and specific formation of prebiotic catalysts. This work demonstrates experimentally, for the first time, substrate-directed formation of an oligopeptide that possesses a specific catalytic activity toward the substrate on which it was formed. In our experiments we used the substrate O-nitrophenol-beta-D-galactopyranoside (ONPG) as a molecular template for the synthesis of a specific catalyst that is capable of cleaving the same substrate. This was achieved by incubation of the substrate with free amino acids and a condensing agent (dicyandiamide) at elevated temperatures. A linear increase with time of the reaction rate (d[product]/d2t), pointed to an acceleration regime, where the substrate generates the formation of the catalyst. The purified catalyst, produced by a substrate-directed mechanism, was analyzed, and identified as Cys2-Fe+2. The mechanism of substrate-directed formation of prebiotic catalysts provides a solution to both the specificity and the reproducibility requirements from any prebiotic system which should evolve into the biological world.

BETA-GALACTOSIDASE OF STREPTOCOCCUS LACTIS

Citti, J. E. (Oregon State University, Corvallis), W. E. Sandine, and P. R. Elliker. beta-Galactosidase of Streptococcus lactis. J. Bacteriol. 89:937-942. 1965.-Synthesis of beta-galactosidase by several strains of Streptococcus lactis was induced by lactose. The rate of hydrolysis of o-nitrophenyl-beta-d-galactopyranoside was used to measure enzyme activity. The enzyme of all but one strain was unstable when whole cells were sonic-treated or treated with toluene; the enzyme of one strain of S. lactis was stable to these treatments, which resulted in at least a fivefold increase in activity over that found in whole cells. The optimal assay conditions for toluene-treated cells of this strain involved incubation at 37 C in pH 7.0 sodium phosphate buffer. Lactose was the most effective inducer of enzyme synthesis. Methyl-beta-d-thiogalactopyranoside, isopropyl-beta-d-thiogalactopyranoside, and galactose were also inducers of the enzyme, but were not as effective as lactose. Melibiose, maltose, and calcium lactobionate were poor inducers of enzyme synthesis. Exogenously supplied glucose repressed enzyme synthesis. The means of control of induced beta-galactosidase synthesis in S. lactis was similar to that in Escherichia coli.

Convenient synthesis of beta-(1-->3)-galactosyl disaccharide alpha-glycoside and its analogs as mimic units of mucin-type carbohydrate

beta-Galactosidase from porcine testes induced regioselective transglycosylation from lactose to the 3-position of 2-acetamido glycosides. When alpha-D-GalNAc-OC6H4NO2-p was used as an acceptor, the enzyme synthesized mainly beta-D-Gal-(1-->3)-alpha-D-GalNAc-OC6H4NO2-p with its (1-->6) linked isomer. The use of an inclusion complex of the glycoside acceptor with beta-CD increased the efficiency of transglycosylation by increasing the solubility of the acceptor. In the same way, the use of beta-D-GalNAc-OC6H4NO2-p as acceptor led to the preferential synthesis of beta-D-Gal-(1-->3)-beta-D-GalNAc-OC6H4NO2-p over that of its (1-->6) linked isomer. beta-D-Gal-(1.3)-beta-D-GlcNAc-OC6H4NO2-p was also synthesized with beta-D-GlcNAc-OC6H4NO2-p acceptor by the consecutive use of beta-D-galactosidases from porcine testes and Bacillus circulans. These enzyme reactions are efficient enough to allow the one-pot preparation of the desired disaccharide glycosides.

Expression and characterization of recombinant alpha-galactosidase in baculovirus-infected insect cells

A cDNA encoding coffee bean alpha-galactosidase was subcloned into baculovirus expression vectors, pVL-1393 and pAc-GP67B, for intracellular and extracellular expression in Spodoptera frugiperda (Sf9) insect cells, respectively. The expressed protein (recombinant alpha-galactosidase) was immunologically reactive with antisera raised against its native counterpart isolated from coffee beans and was biologically active towards the substrate p-nitrophenyl alpha-galactopyranoside. The subcellular distribution of recombinant alpha-galactosidase expressed from different vectors was analyzed by Western blotting, immunofluorescent labeling, and electron microscopy. In addition, recombinant alpha-galactosidase was compared to the native enzyme with respect to glycosylation, thermostability, and pH profile. Furthermore, a recombinant alpha-galactosidase molecule with a His6 tag at its C-terminus was constructed by an overlap PCR method so that the enzyme expressed in Sf9 cells can be purified by a simple affinity chromatography procedure.

Efficient gene transfer to pancreatic islets mediated by adenoviral vectors

Genetic manipulation of pancreatic islets before transplantation has the potential to alter cellular immunity as well as islet function. The purpose of this study was to examine the feasibility of gene transfer to islets, using replication-defective adenoviral vectors. Newborn mouse islets were infected with AdHCMVsp1LacZ vector encoding Escherichia coli beta-galactosidase (beta-gal). Islets were cocultured with vector, at virus-to-target cell ratios of 10:1, for 1 hr. Gene transfer was assessed by specific histochemical stain for beta-gal (X-gal). Islet DNA and RNA were analyzed by Southern and PCR for beta-gal and adeno sequences, and recombinant protein production by western and ONPG assays. Islet integrity after gene transfer was assessed by static incubations and transplantation to nondiabetic and to diabetic mice. Southern analysis and PCR confirmed the presence of E coli beta-galactosidase and the E4 adeno DNA in infected islets, but not in controls. Reverse-transcription PCR and western analysis demonstrated expression and protein production of inserted E coli beta-galactosidase, but not E4 message. Insulin release in response to static incubations was unimpaired in infected islets. Syngeneic islet grafts stained positively for insulin for up to 7 days. Transplanted, genetically manipulated islets functioned similarly to control islets in reversing murine drug-induced diabetes. Thus, gene transfer into islets can be accomplished using adenovirus-based vectors. The capacity of this virus to infect non-dividing cells allows insertion of cDNA into pancreatic islets, with potential application to the transplant setting.

Identification of beta-galactosidase activity in purified bovine retinal rod outer segments

We have identified beta-galactosidase activity in purified bovine rod outer segments (ROS), using rho-nitrophenyl-beta-D-galactopyranoside (PNPG) and chlorophenol red-beta-D-galactopyranoside (CPRG) as substrates. This glycosylhydrolase activity did not appear to represent contamination from other retinal subcellular fractions, based upon the relative specific activities of beta-galactosidase vs. other hydrolases (N-acetyl-beta-glucosaminidase, alpha- and beta-mannosidase, alpha-fucosidase, and acid phosphatase) in bovine retina and ROS homogenates. Using PNPG as a substrate, two pH optima were observed (at 3.5 and 5.5), while the hydrolysis of CPRG exhibited a single, broad pH optimum centered at 5.5. In contrast, hydrolysis of PNPG and CPRG by retinal homogenates exhibited single pH optima, at 3.5 and 5.5., respectively. ROS beta-galactosidase activity increased linearly with time, temperature, and protein concentration, and obeyed Michaelis-Menten kinetics with both substrates. For PNPG, Vmax approximately 88 nmol/h/mg protein and the apparent Km approximately 147 microM. For CPRG, Vmax approximately 33 nmol/h/mg protein and the apparent Km approximately 50 microM. ROS beta-galactosidase activity was affected by carbohydrates and their derivatives: glucose, fucose, sucrose, maltose and N-acetyl-galactosamine were found to stimulate the activity, while D-galactono-gamma-lactone and, to a lesser extent, D-galactose were inhibitory. The enzyme activity also was slightly stimulated by [Cl-] and markedly by dithiothreitol (DTT), while rho-chloro-mercuribenzoic acid (PCMB) and rho-hydroxymercuribenzoic acid (PHMB) inactivated the enzyme. In addition, the enzymatic activity was also found to be differentially sensitive to various anionic and nonionic detergents. However, n-octyl-beta-D-glucoside was slightly stimulatory.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental conditions may affect reproducibility of the beta-galactosidase assay

Several experimental conditions and parameters contributing to the determination of beta-galactosidase activity, as proposed in Miller's assay, were studied. Use of the absorbance correction factor and the nature and concentration of permeabilizing agents were taken into account as different experimental conditions. Reaction time, culture volume, and growth stage were investigated as equation parameters. From a quantitative point of view the results, in terms of Miller units, are markedly affected by variation in these conditions. Therefore, to ensure reproducibility it is advisable to use constant values for all the parameters.

Defined substrate technology method for rapid and specific simultaneous enumeration of total coliforms and Escherichia coli from water: collaborative study

The defined substrate technology (DST) method is a reagent system designed to enumerate specific target microbes(s) from a mixture of bacteria. The system simultaneously enumerates total coliforms and Escherichia coli directly from a water sample. The reagent contains o-nitrophenyl-beta-D-galactopyranoside (ONPG), which is hydrolyzed by total coliforms to produce a yellow chromogen, and 4-methylumbeilliferyl-beta-D-glucuronide (MUG), which is hydrolyzed and fluoresces when E. coli organisms grow. Noncoliform bacteria are suppressed and cannot metabolize the indicator nutrients. Nine laboratories participated in a field evaluation of the method, which covered a wide range of surface and subsurface water sources and water-processing modalities, including the examination of natural samples. The DST system was compared to multiple-tube fermentation (MTF) (quantitative) and presence-absence (P-A) (qualitative) Standard Methods formats. Comparison of water samples from natural sources by using the most probable number (MPN) procedure showed that the DST test was equivalent to the currently used MTF test. Results from the DST and the qualitative P-A procedure showed that these tests agreed with each other in 94% of the water samples analyzed. Specificity of the DST method was established by subculturing a species consistent with a total coliform or E. coli from each positive tube. Eight laboratories participated in a collaborative study of the method. Each laboratory received 3 concentrations of E. coli (organisms/100 mL); 10 (low); 60 (medium); and 120 (high). The DST test was inoculated from a split sample of each bacterial density in parallel with Standard Methods brilliant green lactose broth.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of creatine kinase in the sera of patients with myocardial infarction by a rho-nitrophenylglyoxal method

We have developed a new colorimetric method for the determination of creatine kinase (CK). This method is based on the reaction of creatine, formed enzymatically from creatine phosphate and ADP, with rho-nitrophenylglyoxal (PNPG) under mild alkaline conditions to produce a coloured complex which absorbs maximally at 480 nm. This method was applied to the sera of patients with myocardial infarction. The results obtained by the PNPG method agreed well with the results obtained by other available methods for CK. However, the PNPG method was more convenient and less expensive than other methods and required a single chromogenic reagent. The PNPG method might be easily adapted to routine clinical application.

[A combined chromogenic-fluorogenic medium for the simultaneous detection of coliform groups and E. coli in water]

A comparison was made with different chromogenic and fluorogenic substrates, 4-methylumbelliferyl-beta-D-glucuronide (MUG), 4-nitrophenyl-beta-D-glucuronide (PNPG), 4-methylumbelliferyl-beta-D-galactopyranoside (MUGA), 2-nitrophenyl-beta-D-galactopyranoside (ONPG), 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-GAL), for the rapid and simultaneous enumeration of total coliforms and E. coli in water samples, based on 2 commercially available culture-media. The combination of the chromogenic compound X-GAL (for detecting coliforms) and of the fluorogenic compound MUG (for detecting E. coli) incorporated either into ECD agar or into lauryl sulfate broth proved to be most useful. The optimum concentration of the X-GAL/MUG supplement was (50 micrograms/ml/70 micrograms/ml) for the solid medium (EMX agar) and (60 micrograms/ml/70 micrograms/ml) for the fluid medium (LMX broth). As a result of the examination of 244 Enterobacteriaceae strains isolated from water samples and clinical material, it was shown that the use of EMX agar (LMX broth) had several advantages over conventional methods. A routine method for the analysis of water samples was proposed involving the EMX agar and the LMX broth.

Mutagenicity of rutin and the glycosidic activity of cultured cell-free microbial preparations of human faeces and saliva

Genotoxic testing of flavonol glycosides, which account for most of the human intake of flavonoids, is dependent on the use of enzymatic extracts that exhibit beta-glycosidic activity. This study was aimed at characterizing further the beta-glycosidic activity of cultured cell-free microbial extracts from human faeces (faecalase) and saliva (salivase). Using o-nitrophenyl-beta-D-galactoside as substrate, the optimum pH and apparent Km and energy of activation were shown to be 7.6, 3.5 x 10(-4) M and 8.65 kcal/mol, respectively, for faecalase, and 7.4, 8.7 x 10(-5) M and 3.8 kcal/mol, respectively, for salivase. Rutin (quercetin-3-O-rutinoside) was shown to be a competitive inhibitor for faecalase, whereas no inhibitory activity could be found for salivase. Enzymatic hydrolysis of rutin gave the mutagenic product quercetin that was detected in the Ames assay and using high-performance liquid chromatography.

A simple assay for DNA transfection by incubation of the cells in culture dishes with substrates for beta-galactosidase

Transfection efficiency of different cell types as well as promoter strength of cloned genes can be easily determined by direct assay of beta-galactosidase activity encoded from recombinant genes containing the E. coli beta-galactosidase gene. A substrate for beta-galactosidase, o-nitrophenyl-beta-D-galactopyranoside (ONPG), can be added to dishes containing the transfected cells, and the intensity of the colored enzyme product released from either the intact cell or cells lysed in the dishes can be determined. The results obtained by this assay are a reliable measure of transfection efficiency as well as promotor strength of the genes introduced into the cells. In addition, cells expressing the transfected gene can be identified and quantitated under a light microscope after incubation with X-gal. Thus, it is more convenient to use the E. coli beta-galactosidase gene than the chloramphenicol acetyltransferase gene as a reporter gene in the evaluation of DNA transfection.

Purification and characterisation of an inducible beta-galactosidase from Corynebacterium murisepticum

The beta-galactosidase (EC 3.2.1.32) of Corynebacterium murisepticum (inducible by lactose and galactose) was purified by successive column chromatography on Sephadex G-200, DEAE-Sephadex A-50 and DEAE-cellulose (DE52). The enzyme was found to be a dimer of identical subunits of molecular mass 100,000 daltons. The Km values of the enzyme for the substrates lactose and o-nitrophenyl-beta-D-galactopyranoside (ONPG) are 16.7 mM and 4.4 mM, respectively, indicating, its low affinity for the substrates. The Ouchterlony immunodiffusion method exhibited immunological homogeneity of the enzyme preparation. The catalytic site of the enzyme does not take part in antigen-antibody reaction.

Establishment of a highly sensitive enzyme-linked immunosorbent assay for interleukin-1 alpha employing a fluorogenic substrate

We have previously established a non-competitive solid-phase enzyme-linked immunosorbent assay (ELISA) specific for interleukin-1 alpha (IL-1 alpha) using a combination of polyclonal antibody as the immobilized antibody, biotinylated monoclonal antibody as the second antibody and avidin-peroxidase. The level of detection of that ELISA was 200-500 pg/ml. In order to improve its sensitivity, we have used streptavidin-beta-D-galactosidase and the fluorogenic substance 4-methylumbelliferyl-D-galactopyranoside as enzyme substrate. With this system IL-1 alpha could be detected at concentrations as low as 10-50 pg/ml, which was about 10-20 times more sensitive than conventional mouse thymocyte co-stimulator assays. Furthermore, the assay system was specific for IL-1 alpha in that neither IL-1 beta nor interleukin-2 (IL-2) interfered.

Septicaemia due to Neisseria lactamica--initial confusion with Neisseria meningitidis

Neisseria lactamica, isolated from a baby with septicaemia, was at first thought to be Neisseria meningitidis, possibly acquired in hospital. Extensive investigation of contacts was made until the O-nitrophenyl-D-galactopyranoside reaction proved positive. Distinction between the two species, easily made in this way, is important both in individual patients and in population surveys.

Enzyme-enhancement immunoassay: a homogeneous assay for polyvalent ligands and antibodies

A homogeneous enzyme immunoassay for proteins has been developed that avoids the need for a labeled antigen. The technique involves antibody labeled with beta-galactosidase (EC 3.2.1.23), succinylated antibody, and a macromolecular o-nitrophenyl-beta-galactoside substrate. The enzyme-labeled antibody and the succinylated antibody form an immune complex in the presence of sample antigen. An enzyme within this negatively charged microenvironment produces a product that forms a second light-scattering phase, whereas the product produced by free enzyme remains soluble. Thus the antigen modulates the rate of increase in light scattering. The technique has been applied to assays for human immunoglobulin G and C-reactive protein as well as for specific antibodies.

The anomeric specificity of beta-galactosidase and lac permease from Escherichia coli

Beta-Galactosidase was found to act on alpha-lactose slightly more than twice as rapidly as on beta-lactose for both the hydrolysis and transgalactosylis reactions. The effect was shown to be on the Vmax values; the Km values for the different anomeric forms were the same. The step of the reaction for which the enzyme has anomeric specificity was shown to be glycosidic bond breakage. The steps in glucose release or in the glucose acceptor reaction were not affected by anomeric composition. Neither allolactose hydrolysis nor transport of lactose into the cells by lac permease was sensitive to the anomeric composition of the substrate. The implications of these results for lac operon induction and for lactose metabolism are discussed.

Influence of "energization" on the binding of M protein with p-nitrophenyl alpha-D-galactopyranoside

A specific binding of p-nitrophenyl alpha-D-galactopyranoside has been measured by flow dialysis with Escherichia coli ML 308225 membrane vesicles containing the lac carrier protein. The number of binding sites, 0.45 nmol/mg of membrane protein, remains unchanged in the presence or absence of energy. On the other hand, "energization" increases the M protein affinity for p-nitrophenyl alpha-D-galactopyranoside. The dissociation constant (Kd) is 4 and 21 microM in the presence and absence, respectively, of D-lactate. The same energization effects are found with E. coli A3245 membrane vesicles. p-Nitrophenyl alpha-D-galactopyranoside can be used as a substrate to study energization effect on binding to the lactose permease M protein. These results corroborate observations that energy increases the lac carrier protein affinity for its substrate, and they also confirm the concentration of the M protein, which corresponds to 1.4% of the membrane protein.

Circular dichroism studies of the binding of o-nitrophenyl-beta-D-fucoside and o-nitrophenyl-beta-D-galactoside to lac repressor

The binding of o-nitrophenyl-beta-D-fucoside and o-nitrophenyl-beta-D-galactoside to Escherichia coli lac repressor was investigated by circular dichroism in the wavelength range 300--400 nm corresponding to the o-nitrophenyl chromophores. The CD signal of both ligands drastically changed when they bound to lac repressor due to the asymmetric interaction of the o-nitrophenyl ring with chemical groups of protein. The CD spectra of bound ligands indicate close similarity between the environment of o-nitrophenyl-beta-D-fucoside and o-nitrophenyl-beta-D-galactoside on lac repressor. The CD signal is used to calculate the binding parameters (K and n) to lac repressor. It is demonstrated that the limited proteolytic digestion of lac repressor which gives a 'core protein' does not affect the environment of both ligands on the protein.

The orthonitrophenyl-beta-D-galactoside hydrolase from Pseudomonas aeruginosa (0: 11 serotypes) is a superficial enzyme

About 95% fo the 0: 11 strains of Pseudomonas aeruginosa was able to hydrolyze orthonitrophenyl-beta-D-galactopyranoside (ONPG), but was unable to use lactose. The ONPG-hydrolyzing enzyme was located essentially in the periplasm, as seen by biochemical and ultrastructural studies.

A p-nitrophenyl alpha-galactoside hydrolase from Pseudomonas atlantica. Localization of the enzyme

A p-nitrophenyl alpha-galactoside hydrolase is partially released when whole cells of Pseudomonas atlantica are converted to spheroplasts. The p-nitrophenyl alpha-glactoside hydrolase is completely inactivated by treatment of whole cells with diazonaphthalene -- disulfonic acid (NDS), a reagent which does not penetrate the cytoplasmic membrane. Under the conditions used no inactivation of lactic acid dehydrogenase was observed. A specific staining procedure for this enzyme for use in electron microscopy was developed. The results with this technique in conjunction with the results of spheroplasting and NDS localization suggest that p-nitrophenyl alpha-galactoside hydrolase is located in or on the double-track membranes, primarily on the outer double track.

Purification and properties of beta-galactosidase from Aspergillus oryzae

Beta-Galactosidase [EC 3.2.1.23] has been purified from a culture of Aspergillus oryzae by 2-propanol fractionation, column chromatography on DEAE-Sephadex A-50 and Sephadex G-200. The preparation was homogeneous on ultracentrifugation and disc electrophoresis. The enzyme showed pH optima of 4.5 with ONPG-1 as a substrate and 4.8 with lactose as a substrate. The stable pH range was from 4.0 to 9.0 and the optimum temperature was 46 degrees. The Michaelis constants were 7.2 X 10-minus 4 M with ONPG and 1.8 X 10-minus 2 M with lactose. Hg-2+, Cu-2+, N-bromosuccinimide, and sodium laurylsulfate caused marked inhibition. The apparent molecular weight was calculated to be about 105,000 by Sephadex gel filtration and sucrose density gradient centrifugation.