Carbonic anhydrase inhibitors: Inhibition of the tumor-associated isozymes IX and XII with polyfluorinated aromatic/heterocyclic sulfonamides

The tumor-associated transmembrane carbonic anhydrase (CA, EC 4.2.1.1) isozymes IX (CA IX) and XII (CA XII) are involved in acidification of hypoxic tumors, a process correlated with poor prognosis and clinical outcome of patients harboring such tumors. This process may be reversed by inhibiting these enzymes with potent sulfonamide/sulfamate inhibitors. A series of such aromatic/heterocyclic sulfonamides incorporating 2,3,5,6-tetrafluorobenzoyl-, 2,3,5,6-tetrafluoro- phenylsulfonyl- and pentafluorophenylureido moieties has been investigated for its interaction with the catalytic domain of the human isozymes hCA IX and hCA XII. Some of these compounds showed excellent inhibitory properties against both isozymes IX and XII, with several subnanomolar inhibitors detected for the first time. These sulfonamides may constitute valuable candidates for the development of novel antitumor therapies based on the inhibition of such tumor-associated CA isozymes.     

Cloning,over expression and functional attributes of serine proteases from Oceanobacillus iheyensis O.M.A18 and Haloalkaliphilic bacterium O.M.E12

Cloning, over-expression, characterization and structural and functional analysis of two alkaline proteases from the newly isolated haloalkaliphilic bacteria: Oceanobacillus iheyensis O.M.A₁8 and Haloalkaliphilic bacterium O.M.E₁2 were carried out. The cloned protease genes were over-expressed in Escherichia coli within 6 h of the IPTG induction. The protease genes were sequenced and the sequence submitted to the GenBank with the accession numbers, HM219179 and HM219182. The recombinant proteases were active in the range of pH 8–11 and temperature 30–50 °C. The amino acid sequences of the alkaline proteases displayed hydrophobic character and stable configurations. The amino acids Asp 141, His 171 and Ser 324 formed the catalytic triad, while Ile, Leu and Ser were other amino acid moieties present in the active site. The characteristics of the recombinant proteases were compared and found to be similar to their native counterparts. On the basis of the in-silico analysis and inhibitor studies, the enzymes were confirmed as serine proteases. The study hold significance as only limited enzymes from the haloalkaliphilic bacteria have been cloned, sequenced and analyzed for the structure and function analysis.     

Applications of Hydrolytic and Decarboxylating Enzymes in Biotransformations

Peptides, and oligosaccharides and glycosides, can be synthesised by making use of the ‘reverse hydrolytic activity’ of proteases and glycosidases respectively. In applying these enzymes to the practical synthesis of these classes of compound, several factors need to be considered, namely the need to shift the rate-determining step through the use of activated substrates, the need to minimise competing hydrolysis of these and the need to minimise hydrolysis of the products. In spite of these problems, the enzymatic methods have many attractive features, not least amongst which is the absolute control of stereochemistry in acyl transfer and glycosyl transfer respectively.     

Defect of Fe-S cluster binding by DNA polymerase δ in yeast suppresses UV-induced mutagenesis,but enhances DNA polymerase ζ – dependent spontaneous mutagenesis

Eukaryotic genomes are duplicated by a complex machinery, utilizing high fidelity replicative B-family DNA polymerases (pols) α, δ and ε. Specialized error-prone pol ζ, the fourth B-family member, is recruited when DNA synthesis by the accurate trio is impeded by replication stress or DNA damage. The damage tolerance mechanism dependent on pol ζ prevents DNA/genome instability and cell death at the expense of increased mutation rates. The pol switches occurring during this specialized replication are not fully understood. The loss of pol ζ results in the absence of induced mutagenesis and suppression of spontaneous mutagenesis. Disruption of the Fe-S cluster motif that abolish the interaction of the C-terminal domain (CTD) of the catalytic subunit of pol ζ with its accessory subunits, which are shared with pol δ, leads to a similar defect in induced mutagenesis. Intriguingly, the pol3-13 mutation that affects the Fe-S cluster in the CTD of the catalytic subunit of pol δ also leads to defective induced mutagenesis, suggesting the possibility that Fe-S clusters are essential for the pol switches during replication of damaged DNA. We confirmed that yeast strains with the pol3-13 mutation are UV-sensitive and defective in UV-induced mutagenesis. However, they have increased spontaneous mutation rates. We found that this increase is dependent on functional pol ζ. In the pol3-13 mutant strain with defective pol δ, there is a sharp increase in transversions and complex mutations, which require functional pol ζ, and an increase in the occurrence of large deletions, whose size is controlled by pol ζ. Therefore, the pol3-13 mutation abrogates pol ζ-dependent induced mutagenesis, but allows for pol ζ recruitment for the generation of spontaneous mutations and prevention of larger deletions. These results reveal differential control of the two major types of pol ζ-dependent mutagenesis by the Fe-S cluster present in replicative pol δ.     

Diel vertical migration ofEudiaptomus gracilis during a short summer period

Several aspects of a diel vertical migration (DVM) of adultEudiaptomus gracilis in Lake Maarsseveen (The Netherlands) are described. The period of DVM lasted from the end of May until the middle of August. On May 21, 1989, the population was found divided into a deep dwelling part and a part in the upper five meter. Large shoals of juvenile perch were observed in the open water for the first time. On June 7, the whole population was down below 10 m and concentrated in a zone of high chlorphyll-a concentrations. One week later, a regular DVM was performed. The amplitude of this migration gradually decreased towards the end of the migration period. The ascent in the evening and the descent in the morning took place after sunset and before sunrise, respectively. The movements coincided with high relative changes in light intensity. Population size increased rapidly during the period of DVM but decreased again before the end of this period.     

Expression of Aspergillus niger N5-5 in E. coli and purification and identification of products

Due to the feature of high hydrolysis, tannase is widely used in food, beverage, brewing and other fields. However, high cost in producing natural tannase makes it difficult to apply tannase to industry in a large-scale. Microbial expression systems can be used for preparing numerous amount of enzyme at low cost, so in this paper Aspergillus niger N5-5 was expressed using E. coli system. Specific primers were designed based on the Aspergillus niger N5-5 sequence N3 (GenBank, No.: KP677552), and tannase gene tan was promoted to carry 6 His tag and enzyme cutting site which contains NdeI/HindIII using PCR amplification. Then, tannase gene tan was connected to expression vector by NdeI/HindIII enzyme cutting. In this way, recombinant expression vector tan-pET43.1a was formed. Then, the expression vector pET43.1a by NdeI/HindIII enzyme cutting was transformed into E. coli BL21 (DE3) to induce expression of Aspergillus niger N5-5. When the induced fungi were disrupted by the ultrasonic wave, the crude enzyme was extracted and purified by using the IMAC, and then the activity of the crude enzyme and pure enzyme was determined. According to the results of determination of the tannase activity, the tannase activity of the crude enzyme was greatly improved after the crude enzyme was purified, and the specific activity of the pure enzyme was about 8 times of that of the crude enzyme. The results of SDS-PAGE of the pure enzyme showed that the molecular mass of the pure enzyme was about 65 kDa/64–65 kDa, which was consistent with the expected result (64.2 kDa), It can be concluded that the crude enzyme solution was purified successfully. The results of pure enzyme’s protein identification by Western Blotting showed that clear protein bands pro-3 were observed. Molecular mass of clear protein bands pro-3 was about 65 kDa, which was in line with the expected results (64.2 kDa). It can be seen that the aforementioned expression protein could be specifically combined with His tag. It proved expression protein to be a recombinant fusion protein with 6 His tag.     

The lifetime of molecular (Davydov) solitons

The lifetime of Davydov solitons in a one-dimensional system is studied theoretically. The process of thermalization and the properties of solitons at finite temperature are investigated and the processes of soliton creation and disintegration are discussed.