New development in in-capillary electrophoresis techniques for kinetic and inhibition study of enzymes

Enzymes are often quantified by measuring their biological activity. Capillary electrophoresis is gaining its position in this field due to the ongoing trend to miniaturize biochemical assays.     

Enzymatic synthesis and the structure elucidation of novel trisaccharides comprised of D-galactose,N-acetyl-D-glucosamine,and D-fructose

Enzymatic synthesis of trisaccharides from N-acetylsucrosamine and lactose utilizing the transgalactosylation activity of Aspergillus oryzae β-galactosidase provided two reaction products. Structure analyses by various 2D NMR spectroscopy and MS indicated that the products were β-D-fructofuranosyl β-D-galactopyranosyl-(1→6)-2-acetamido-2-deoxy-α-D-glucopyranoside and β-D-galactopyranosyl-(1→6)-β-D-fructofuranosyl-(2?1)-2-acetamido-2-deoxy-α-D-glucopyranoside. Moreover, J-resolved-HMBC experiments indicated that the conformations around the glycosidic bonds of these trisaccharides were very similar. Examination about the pH and thermal stabilities of the glycosidic bonds in the GlcNAc–Fru moiety of the two trisaccharides indicated apparent difference.     

A Galactosidase-Activatable Fluorescent Probe for Detection of Bacteria Based on BODIPY

Pathogenic E. coli infection is one of the most widespread foodborne diseases, so the development of sensitive, reliable and easy operating detection tests is a key issue for food safety. Identifying bacteria with a fluorescent medium is more sensitive and faster than using chromogenic media. This study designed and synthesized a β-galactosidase-activatable fluorescent probe BOD-Gal for the sensitive detection of E. coli. It employed a biocompatible and photostable 4,4-difluoro-3a,4a-diaza-s-indancene (BODIPY) as the fluorophore to form a β-O-glycosidic bond with galactose, allowing the BOD-Gal to show significant on-off fluorescent signals for in vitro and in vivo bacterial detection. This work shows the potential for the use of a BODIPY based enzyme substrate for pathogen detection.     

Characterization of an Isozyme of β-Glucosidase from Sweet Almond

A sweet almond β-glucosidase (EC 3.2.1.21) isozyme was purified from commercial crude product. The process of purification consisted of a Protein-Pak Q anion exchange chromatography following by a Superdex 75 HR gel filtration separation. The purified enzyme is a monomeric glycoprotein with molecular weight of 58 kDa and pI=4.55 which is distinguished from reported isozymes. The enzyme has apH optimum in the range of 5.2-5.6 when p-nitrophenyl-β-D-glycopyranosides are used as substrate and is stable up to 50 °C at that pH range. The purified protein also exhibits profound β-galactosidase and σ-L-arabinosidase activity. The study of substrate specificity revealed that lacking of hydroxymethyl group at C-5 of glycosides resulted in higher affinity for substrate binding to enzyme, whereas the chemical step of hydrolysis (k_cst) was prevented significantly. The pH activity profile displayed a bell-shaped curve for all measured p-nitrophenyl-β-D-glycopyranosides with apparent pK₁ and pK₂ values of 4.4-4.7 and 6.2-6.4, respectively. This isozyme was strongly inhibited by δ-gluconolactone (K_i = 160 μM) and 4-phenylimidazole (K_i = 17.8 μM) reversibly at pH 6.2. Among the tested glycoses, the binding affinity of N-acetyl-β-D-glucosamine to the enzyme (K_l = 52 mM) was 6 times stronger than that of glucose and its epimers.     

A Simple and Rapid Method of Identification of Extracellular Plant Galactosidases

A simple, rapid, and sensitive procedure for the identification of plant extracellular - and -galactosidase is described using callus cultures of seedlings from the tested plant, roots of 4-6 day old seedlings of Californian poppy germinating on agar plates, and cell suspension cultures cultivated from callus cultures. Synthetic substrates were used for the determination of the intra- and extracellular activities of - and -galactosidase. Many imino- or azasugars are strong glycosidase inhibitors, and some of them show promising chemotherapeutic effects against viral disease and are potential antidiabetic as well as antitumor agents. This fact aroused our interest for a rapid and sensitive assay method of the activity of - and -galactosidases of plant origin. The results presented here show the perspective usefulness of extracellular galactosidases of plant origin in inhibitory and/or biotechnological studies.     

Pharmacological chaperone therapy for Fabry disease

Fabry disease is an inherited lysosomal storage disorder caused by deficient α-galactosidase A activity. Many missense mutations in Fabry disease often cause misfolded gene products, which leads to their retention in the endoplasmic reticulum by the quality control system; they are then removed by endoplasmic reticulum-associated degradation. We discovered that a potent α-galactosidase A inhibitor, 1-deoxygalactonojirimycin, acts as a pharmacological chaperone to facilitate the proper folding of the mutant enzyme by binding to its active site, thereby improving its stability and trafficking to the lysosomes in mammalian cells. The oral administration of 1-deoxygalactonojirimycin to transgenic mice expressing human mutant α-galactosidase A resulted in significant increases in α-galactosidase A activity in various organs, with concomitant reductions in globotriaosylceramide, which contributes to the pathology of Fabry disease. Seventy-eight missense mutations were found to be responsive to 1-deoxygalactonojirimycin. These data indicate that many patients with Fabry disease could potentially benefit from pharmacological chaperone therapy.     

Synthesis of a New β-Galactosidase Inhibitor Displaying Pharmacological Chaperone Properties for GM1 Gangliosidosis

GM1 gangliosidosis is a rare lysosomal disease caused by the deficiency of the enzyme β-galactosidase (β-Gal; GLB1; E.C. 3.2.1.23), responsible for the hydrolysis of terminal β-galactosyl residues from GM1 ganglioside, glycoproteins, and glycosaminoglycans, such as keratan-sulfate. With the aim of identifying new pharmacological chaperones for GM1 gangliosidosis, the synthesis of five new trihydroxypiperidine iminosugars is reported in this work. The target compounds feature a pentyl alkyl chain in different positions of the piperidine ring and different absolute configurations of the alkyl chain at C-2 and the hydroxy group at C-3. The organometallic addition of a Grignard reagent onto a carbohydrate-derived nitrone in the presence or absence of a suitable Lewis Acid was exploited, providing structural diversity at C-2, followed by the ring-closure reductive amination step. An oxidation-reduction process allowed access to a different configuration at C-3. The N-pentyl trihydroxypiperidine iminosugar was also synthesized for the purpose of comparison. The biological evaluation of the newly synthesized compounds was performed on leucocyte extracts from healthy donors and identified two suitable β-Gal inhibitors, namely compounds 10 and 12. Among these, compound 12 showed chaperoning properties since it enhanced β-Gal activity by 40% when tested on GM1 patients bearing the p.Ile51Asn/p.Arg201His mutations.