Histone deacetylase 6 (HDAC6) is an unique subtype of histone deacetylases with two tandem deacetylase domains and substrate specificity for non-histone proteins. It is involved in many important physiological and pathological processes and has become a promising therapeutic target in recent decades. Different kinds of potent HDAC6-selective inhibitors have been reported around the world. This paper reviews the progress in the study of structure and functions of HDAC6 as well as the development of HDAC6-selective inhibitors.
Histone Deacetylase Inhibitors ; pharmacology ; Histone Deacetylases ; chemistry ; Humans ; Substrate Specificity

We introduce a computational approach for analysis of glycosylation in Post-PKS tailoring steps. It is a computational method to predict the deoxysugar biosynthesis unit pathway and the substrate specificity of glycosyltransferases involved in the glycosylation of polyketides. In this work, a directed and weighted graph is introduced to represent and predict the deoxysugar biosynthesis unit pathway. In addition, a homology based gene clustering method is used to predict the substrate specificity of glycosyltransferases. It is useful for the rational design of polyketide natural products, which leads to in silico drug discovery.
Biological Agents ; Computer Simulation ; Glycosylation ; Glycosyltransferases ; Polyketides ; Substrate Specificity

2-Haloacid dehalogenases (EC 3.8.1.X) catalyze the hydrolytic dehalogenation of 2-haloacids, releasing halogen ions and producing corresponding 2-hydroxyacids. The enzymes not only degrade xenobiotic halogenated pollutants, but also show wide substrate profile and astonishing efficiency for enantiomer resolution, making them valuable in environmental protection and the green synthesis of optically pure chiral compounds. A variety of 2-haloacid dehalogenases have been biochemically characterized so far. Further studies have been made in protein crystal structures and catalytic mechanisms. Here, we review the recent progresses of 2-haloacid dehalogenases in their source, protein structures, reaction mechanisms, catalytic properties and application. We also suggest further research directions for 2-haloacid dehalogenase.
Catalysis ; Halogenation ; Hydrolases ; chemistry ; metabolism ; Hydrolysis ; Research ; trends ; Substrate Specificity

As a class of multifunctional biocatalysts, halohydrin dehalogenases are of great interest for the synthesis of chiral β-substituted alcohols and epoxides. There are less than 40 halohydrin dehalogenases with relatively clear catalytic functions, and most of them do not meet the requirements of scientific research and practical applications. Therefore, it is of great significance to excavate and identify more halohydrin dehalogenases. In the present study, a putative halohydrin dehalogenase (HHDH-Ra) from Rhodospirillaceae bacterium was expressed and its enzymatic properties were investigated. The HHDH-Ra gene was cloned into the expression host Escherichia coli BL21(DE3) and the target protein was shown to be soluble. Substrate specificity studies showed that HHDH-Ra possesses excellent specificity for 1,3-dichloro-2-propanol (1,3-DCP) and ethyl-4-chloro-3-hydroxybutyrate (CHBE). The optimum pH and temperature for HHDH-Ra with 1,3-DCP as the reaction substrate were 8.0 and 30 °C, respectively. HHDH-Ra was stable at pH 6.0-8.0 and maintained about 70% of its original activity after 100 h of treatment. The thermal stability results revealed that HHDH-Ra has a half-life of 60 h at 30 °C and 40 °C. When the temperature is increased to 50 °C, the enzyme still has a half-life of 20 h, which is much higher than that of the reported enzymes. To sum up, the novel halohydrin dehalogenase from Rhodospirillaceae bacterium possesses good temperature and pH stability as well as catalytic activity, and shows the potential to be used in the synthesis of chemical and pharmaceutical intermediates.
Escherichia coli/metabolism* ; Hydrolases/metabolism* ; Rhodospirillaceae ; Substrate Specificity

Human secreted phospholipase A2 GIIE (hGIIE) is involved in inflammation and lipid metabolism due to its ability of hydrolyzing phospholipids. To reveal the mechanism of substrate head-group selectivity, we analyzed the effect of mutation of hGIIE on its activity and selectivity. hGIIE structural analysis showed that E54 might be related to its substrate head-group selectivity. According to the sequence alignment, E54 was mutated to alanine, phenylalanine, and lysine. Mutated genes were cloned and expressed in Pichia pastoris X33, and the enzymes with mutations were purified with 90% purity by ion exchange and molecular size exclusion chromatography. The enzymatic activities were determined by isothermal microthermal titration method. The Km of mutant E54K towards 1,2-dihexyl phosphate glycerol decreased by 0.39-fold compared with that of wild type hGIIE (WT), and the Km of E54F towards 1,2-dihexanoyl-sn-glycero-3-phosphocholine increased by 1.93-fold than that of WT. The affinity of mutant proteins with phospholipid substrate was significantly changed, indicating that E54 plays an important role in the substrate head-group selectivity of hGIIE.
Humans ; Kinetics ; Mutation ; Phospholipases A2, Secretory ; Phospholipids ; Saccharomycetales ; Substrate Specificity

α-L-rhamnosidase is a very important industrial enzyme that is widely distributed in a variety of organisms. α-L-rhamnosidase of different origins show functional diversity. For example, the optimal pH of α-L-rhamnosidase from bacteria is close to neutral or alkaline, while the optimal pH of α-L-rhamnosidase from fungi is in the acidic range. Furthermore, the enzymatic properties of α-L-rhamnosidases of different origins differ in terms of the optimal temperature, the thermal stability, and the substrate specificity, which determine the different applications of these enzymes. In this connection, it is crucial to elucidate the similarities and differences in the catalytic mechanism and substrate specificity of α-L-rhamnosidase of different origins through analyzing its enzymatic properties. Moreover, it is important to explore and understand the effects of aglycon and metal cations on enzyme activity and the competitive inhibition of L-rhamnose and glucose on enzymes. These knowledge can help discover α-L-rhamnosidase of industrial significance and promote its industrial application.
Glycoside Hydrolases/metabolism* ; Hydrogen-Ion Concentration ; Rhamnose ; Substrate Specificity ; Temperature

Human cytomegalovirus encodes an unusual protein kinase UL97 which can phosphorylate exogenous substrates, including histone H2B and nucleoside analogs such as ganciclovir. The previous result interestingly showed that the peptides phosphorylated by UL97 have K/R at the 5 positions (P+5) downstream from the pSer. To confirm the importance of the basic residue in the position, we used two peptide libraries, 4S4K (MAXXXXSXXXXKXANNN) and 4S6N (MAXXXXSXXXXXXNNN). The activity of phosphorylation by UL97 was higher in the peptide library 4S4K than 4S6N, suggesting the importance of basic residue at P+5 position. The screening with a peptide library 4S4K showed slight tendencies for N in the P+1 and P+2, M in the P+2, K in the P+4 and P+6 positions and several amino acids in the other positions. This result will give information to develop an optimal peptide for screening a novel UL97 inhibitor.
Amino Acids ; Cytomegalovirus* ; Ganciclovir ; Histones ; Humans* ; Mass Screening* ; Peptide Library* ; Peptides ; Phosphorylation ; Protein Kinases* ; Substrate Specificity*

Xylanase can hydrolyze xylans into xylooligosaccharides and D-xylose, and has great prospect for applications in feed industry, paper and pulp industry, food industry and environment science. The study of xylanase had been started in 1960's. With the development and application of the new technologies, such as molecular biology, structural biology and protein engineering, many progresses have been made in the research of structures and functions of xylanase. This paper reviews the research progress and trend in the structure correlating with the important properties of xylanase. Analyses of three-dimensional structures and properties of mutants have revealed that glutamine and aspartic acid residues are involved in the catalytic mechanism. The thermostability of xylanase correlated with many factors, such as disulfide bridges, salt bridges, aromatic interactions, cotent of arginine and proline, and some multidomain xylanase have thermostability domains in N or C terminal. But no single mechanism is responsible for the remarkable stability of xylanase. The isoelectic points and reaction pH of xylanase are influenced by hydrophobicity and content of electric charges. Many researches had demonstrated that aromatic amino acid, histidine, and tryptophan play an important role in improving enzyme-substrate affinity. The researches of structures and functions of xylanase are of great significance in understanding the catalytic mechanism and directing the improvement of xylanase properties to meet the application requirement.
Catalysis ; Endo-1,4-beta Xylanases ; chemistry ; metabolism ; Enzyme Stability ; Protein Engineering ; Substrate Specificity

Consolidated bioprocessing technology can be used for Kluyveromyces marxianus YX01 to produce ethanol from Jerusalem artichoke, which is one of the potential processes to produce biofuel from non-cereal crops. In this study, we combined the aeration rate with the substrate concentration to conduct cross-over experiments for K. marxinaus YX01, and studied ethanol fermentation and the influence of inulin enzyme activity. The substrate concentration had a little repressive effect on ethanol productivity. When substrate concentration reached 250 g/L under anaerobic conditions, ethanol concentration was 84.8 g/L, and ethanol yield was reduced from 86.4% (50 g/L substrate concentration) to 84.7% of the theoretical value. Aeration rate could accelerate K. marxinaus YX01 ethanol fermentation, but reduced ethanol yield. When substrate concentration reached 250 g/L under aeration at 1.0 vvm, ethanol yield was reduced from 84.7% under anaerobic conditions to 73.3% of the theoretical value. With increased concentration of the carbon source and reduced aeration rate, the inulinase of K. marxinaus YX01 reduced and the concentration of glycerol increased, however, the acetic acid increased with the increased concentration of the carbon source and aeration rate. When substrate concentration reached 250 g/L under anaerobic conditions, inulinase activity was only 6.59 U/mL; when substrate concentration reached 50 g/L under aeration at 1.0 vvm, inulinase activity was 21.54 U/mL.
Ethanol ; metabolism ; Fermentation ; Glycoside Hydrolases ; metabolism ; Helianthus ; metabolism ; Inulin ; metabolism ; Kluyveromyces ; classification ; metabolism ; Substrate Specificity

The prenylation of aromatic compounds plays an important role in the natural product research because it not only gives rise to an astounding diversity of primary and secondary metabolites in plants, fungi and bacteria but also enhances the bioactivities and bioavailabilities of these compounds. However, further investigation of prenylated aromatic compounds is frequently hindered due to their low content in nature and difficulties in chemical synthesis. Cloning aromatic prenyltransferase genes followed by heterologous expression would be attractive tools for the chemoenzymatic synthesis of bioactive molecules. This review summarizes the classifications, structural investigations, enzymatic catalysis and other progress in aromatic prenyltransferases originated from microorganisms.
Bacteria ; enzymology ; Dimethylallyltranstransferase ; biosynthesis ; chemistry ; classification ; Fungi ; enzymology ; Molecular Structure ; Substrate Specificity ; Synthetic Biology