The UDP-sulfoquinovose synthase Agl3 from Sulfolobus acidocaldarius converts UDP-d-glucose and sulfite to UDP-sulfoquinovose, the activated form of sulfoquinovose required for its incorporation into glycoconjugates. Based on the amino acid sequence, Agl3 belongs to the short-chain dehydrogenase/reductase enzyme super-family, together with SQD1 from Arabidopsis thaliana, the only UDP-sulfoquinovose synthase with known crystal structure. By comparison of sequence and structure of Agl3 and SQD1, putative catalytic amino acids of Agl3 were selected for mutational analysis. The obtained data suggest for Agl3 a modified dehydratase reaction mechanism. We propose that in vitro biosynthesis of UDP-sulfoquinovose occurs through an NAD+-dependent oxidation/dehydration/enolization/sulfite addition process. In the absence of a sulfur donor, UDP-d-glucose is converted via UDP-4-keto-d-glucose to UDP-d-glucose-5,6-ene, the structure of which was determined by 1H and 13C-NMR spectroscopy. During the redox reaction the cofactor remains tightly bound to Agl3 and participates in the reaction in a concentration-dependent manner. For the first time, the rapid initial electron transfer between UDP-d-glucose and NAD+ could be monitored in a UDP-sulfoquinovose synthase. Deuterium labeling confirmed that dehydration of UDP-d-glucose occurs only from the enol form of UDP-4-keto-glucose. The obtained functional data are compared with those from other UDP-sulfoquinovose synthases. A divergent evolution of Agl3 from S. acidocaldarius is suggested.

Chito-oligosaccharides (COSs) are bioactive molecules with interesting characteristics; however, their exploitation is still restricted due to limited amounts accessible with current production strategies. Here we present a strategy for the production of COSs based on hydrolysis of chitosan by using readily available glycosidases. Cellobiohydrolases (EC 3.2.1.91) were compared with chitosanases (EC 3.2.1.132) regarding their ability for COS production, and the resulting fractions were analyzed by MS and NMR. The oligosaccharides had a degree of polymerization between three and six units, and the degree of acetylation (DA) varied depending on the applied enzyme. Different cellobiohydrolases produced COSs with varying DA, and based on comprehensive NMR analysis the preferred cleavage sites of the respective enzymes that show chitosanase and chitinase activity were elucidated. The study reveals the high potential of readily available cellulolytic enzymes besides chitosanases for the production of COSs with distinct structure facilitating access to this bioactive compound class.

Chito-oligosaccharides (COSs) are a substance class of high interest due to various beneficial bioactive properties. However, detailed mechanistic and application-related investigations are limited due to the poor availability of COSs with defined structural properties. Here, we present the large-scale production of COSs with defined degree of N-acetylation using a commercial cellulase preparation from Trichoderma longibrachiatum. The enzyme preparation was found to exclusively produce COSs lacking of acetyl groups while MS/MS analysis indicated a cellobiohydrolase to be the responsible for hydrolysis with the enzyme preparation. MS and NMR analysis proved the low content of acetyl groups in the COS mix and oligomers with a degree of polymerization (DP) of 2–6 were obtained. The low cost enzyme source was further exploited for large-scale production in a 20 g batch and resulted a COSs yield of 40%. An inexpensive enzyme source for the production of bioactive COSs was successfully implemented and thorough product analysis resulted in well-defined COSs. This strategy could improve the access to this substance class for a more detailed investigation of its various biological activities.

S OME new sulfathiazole derivatives were synthesized. The sulfathiazole starting material was reacted with ethyl bromoacetate and gave unpredictably an ester product 2. The substitution occurred selectively at the tautomeric proton of the NH thiazolyl nitrogen rather than the aromatic NH 2 protons. The ester was further hydrazinolysed followed by condensation with several aldehydes to establish hydrazones (4a-h). Hantzesch thiazole synthesis was also applied to build antimicrobial agents containing multi-thiazole moieties. The structures of the synthesized compounds were confirmed by 1 H, 13 C, 2D 1 H NMR, MS, and microanalyses. The synthesized compounds were tested for their antimicrobial activity towards Gram-positive and Gram-negative bacteria, and fungi strains. Some of the investigated compounds showed prominent high potency. The docking study revealed the mode of action between the modified sulfathiazole ligands and the binding site of DHPS.

The design, synthesis, and in vitro antiproliferative activity of a novel series of sulfide (4a–i) and sulfoxide (5a–h) derivatives of benzimidazole, in which different aromatic and heteroaromatic acetamides are linked to benzimidazole via sulfide (4a–i) and sulfoxide (5a–h) linker, are reported and the structure-activity relationship is discussed. The new derivatives were prepared by coupling 2-(mercaptomethyl)benzimidazole with 2-bromo-N-(substituted) acetamides in dry acetone in the presence of anhydrous potassium carbonate. With very few exceptions, all of the synthesized compounds showed varying antiprolific activities against HepG2, MCF-7, and A549 cell lines. Compound 5a was very similar in potency to doxorubicin as an anticancer drug, with IC50 values 4.1 ± 0.5, 4.1 ± 0.5, and 5.0 ± 0.6 µg/mL versus 4.2 ± 0.5, 4.9 ± 0.6, and 6.1 ± 0.6 µg/mL against HepG2, MCF-7, and A549 cell lines, respectively. In contrast, none of the compounds showed activity against human prostate PC3 cancer cells. Additionally, the sulfoxide derivatives were more potent than the corresponding sulfides.