Production of two extracellular alkaline phosphatases by a psychrophilic arthrobacter strain

Molecular Biology Applications of Psychrophilic Enzymes: Adaptations, Advantages, Expression, and Prospective

Psychrophilic enzymes are primarily produced by microorganisms from extremely low-temperature environments which are known as psychrophiles. Their high efficiency at low temperatures and easy heat inactivation property have attracted extensive attention from various food and industrial bioprocesses. However, the application of these enzymes in molecular biology is still limited. In a previous review, the applications of psychrophilic enzymes in industries such as the detergent additives, the food additives, the bioremediation, and the pharmaceutical medicine, and cosmetics have been discussed. In this review, we discuss the main cold adaptation characteristics of psychrophiles and psychrophilic enzymes, as well as the relevant information on different psychrophilic enzymes in molecular biology. We summarize the mining and screening methods of psychrophilic enzymes. We finally recap the expression of psychrophilic enzymes. We aim to provide a reference process for the exploration and expression of new generation of psychrophilic enzymes.

Synthesis, Biological Evaluation, 2D-QSAR, and Molecular Simulation Studies of Dihydropyrimidinone Derivatives as Alkaline Phosphatase Inhibitors

The presence of alkaline phosphatases has been observed in several species and has been known to play a crucial role in various biological functions. Higher expressions of alkaline phosphatase have been found in several multifactorial disorders and cancer patients, which has led it to be an interesting target for drug discovery. A strong structural similarity exists between intestinal alkaline phosphatases (IAPs) and tissue-nonspecific alkaline phosphatases (TNAPs), which has led to the discovery of only a few selective inhibitors. Therefore, a series of 22 derivatives of 6-(chloromethyl)-4-(4-hydroxyphenyl)-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate (1) and ethyl 6-(chloromethyl)-4-(2-hydroxyphenyl)-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate (2) were synthesized to evaluate the anticancer potential of these compounds against breast cancer. The compounds were characterized through spectral and elemental analyses. The inhibitory effect of dihydropyrimidinone derivatives on alkaline phosphatases was evaluated using the calf alkaline phosphatase assay. The antioxidant activity of these compounds was performed to study the radical scavenging effect. In silico molecular docking and molecular dynamic simulations were performed to elucidate the binding mode of active compounds. Moreover, the two-dimensional qualitative-structure-activity relationship (2D-QSAR) was performed to study the structural requirements for enzyme inhibition. The calf alkaline phosphatase inhibitory assay revealed significant inhibition of the enzyme by compound 4d with IC₅₀ 1.27 μM at 0.1 mM concentration as compared to standard KH₂PO₄ having IC₅₀ 2.80 μM. The compounds 4f, 4e, and 4i also showed very good inhibition with IC₅₀ values of 2.502, 2.943, and 2.132 μM, respectively, at the same concentration. The antioxidant assay revealed efficient radical scavenging activity of compounds 4f, 4e, and 4g at 100 μg/mL with IC₅₀ values of 0.48, 0.61, and 0.75 μg/mL, respectively. The molecular docking and simulation studies revealed efficient binding of active compounds in the active binding site of the target enzyme. The final QSAR equation revealed good predictivity and statistical validation having R ² = 0.958 and Q ² = 0.903, respectively, for the generated model. The compound 4d showed the highest inhibitory activity with stable binding modes acting as a future lead for identifying alkaline phosphatase inhibitors. The molecular simulations suggested the stable binding of this compound, and the QSAR studies revealed the importance of autocorrelated descriptors in the inhibition of alkaline phosphatase. The investigated compounds may serve as potential pharmacophores for potent and selective alkaline phosphatase inhibitors. We intend to further investigate the biological activities of these compounds as alkaline phosphatase inhibitors.

Probing the high potency of pyrazolyl pyrimidinetriones and thioxopyrimidinediones as selective and efficient non-nucleotide inhibitors of recombinant human ectonucleotidases

With the aim to discover novel, efficient and selective inhibitors of human alkaline phosphatase and nucleotide pyrophosphatase enzymes, two new series of pyrazolyl pyrimidinetriones (PPTs) (6a-g) and thioxopyrimidinediones (PTPs) (6h-n) were synthesized in good chemical yields using Knoevenagel condensation reaction between pyrazole carbaldehydes (4a-g) and pharmacologically active N-alkylated pyrimidinetrione (5a) and thioxopyrimidinedione (5b). The inhibition potential of the synthesized hybrid compounds was evaluated against human alkaline phosphatase (h-TNAP and h-IAP) and ectonucleotidase (h-NPP1 and h-NPP3) enzymes. Most of the tested analogs were highly potent with a variable degree of inhibition depending on the functionalized hybrid structure. The detailed structure-activity relationship (SAR) of PPT and PTP derivatives suggested that the compound with unsubstituted phenyl ring from PPT series led to selective and potent inhibition (6a; IC₅₀ = 0.33 ± 0.02 µM) of h-TNAP, whereas compound 6c selectively inhibited h-IAP isozyme with IC₅₀ value of 0.86 ± 0.04 µM. Similarly, compounds 6b and 6h were identified as the lead scaffolds against h-NPP1 and h-NPP3, respectively. The probable binding modes for the most potent inhibitors were elucidated through molecular docking analysis. Structure-activity relationships, mechanism of action, cytotoxic effects and druglikeness properties are also discussed.

Distinctive inhibition of alkaline phosphatase isozymes by thiazol-2-ylidene-benzamide derivatives: Functional insights into their anticancer role

In the recent years, the role of alkaline phosphatase (AP) isozymes in the cause of neoplastic diseases such as breast, liver, renal, and bone cancer has been confirmed and, thus they represent a novel target for the discovery of anticancer drugs. In this study different derivatives of thiazol-2-ylidene-benzamide were evaluated for their potential to inhibit alkaline phosphatase (AP) isozymes. Their anticancer potential was assessed using human breast cancer (MCF-7), bone-marrow cancer (K-562), and cervical cancer (HeLa) cell lines in comparison to normal cells from baby hamster kidney BHK-21. The results suggested that in comparison to other derivatives, compounds 2i, 2e, and 2a showed more sensitivity towards human tissue non-specific alkaline phosphatase (h-TNAP). Among these, 2″-chloro-N-(3-(4'-fluorophenyl)-4-methylthiazol-2(3H)-ylidene) benzamide (2e) was found as the most potent and selective inhibitor for h-TNAP with an IC₅₀ value of 0.079 ± 0.002 μM. Moreover, a significant correlation was observed between the enzyme inhibition profile and cytotoxic data. The compounds exhibiting maximum anticancer potential also induced maximum apoptosis in the respective cell lines. Furthermore, the DNA interaction studies exhibited the non-covalent mode of interaction with the herring sperm-DNA. Molecular docking studies also supported the in vitro inhibitory activity of potent compounds. Our findings suggested that potent and selective inhibitors might be useful candidates for the treatment or prevention of those diseases associated with the higher level of AP. Moreover, the study can be useful for the researcher to explore more molecular mechanisms of such derivatives and their analogues with the exact findings.

Effect of succinate on phosphate solubilization in nitrogen fixing bacteria harbouring chick pea and their effect on plant growth

Diverse nitrogen fixing bacteria harbouring chick pea rhizosphere and root nodules were tested for multiple plant growth promoting traits like tricalcium phosphate (TCP) and rock phosphate (RP) solubilization, production of ammonia, indole 3-acetic acid, chitinase, phytase and alkaline phosphatase. Isolates belonged to diverse genus like Enterobacter, Acinetobacter, Erwinia, Pseudomonas, Rhizobium, Sinorhizobium, Ensifer, Klebsiella, etc. Most isolates solubilized TCP and RP along with the lowering of media pH, indicating acidification to be the chief mechanism behind this solubilization. However, lowering of media pH and P release decreased by 32-100% when media was supplemented with succinate, a major component of plant root exudates indicating succinate mediated repression of P solubilization. Maximum TCP and RP solubilization with P release of 850μg/mL and 2088μg/mL was obtained with lowering of media pH up to 2.8 and 3.3 for isolate E43 and PSB1 respectively. This pH drop changed to 4.4 and 4.8 with 80% and 87% decrease in P solubilization in the presence of succinate. Maximum 246μg/mL indole 3-acetic acid production in Lh3, 44.8U/mL chitinase activity in MB3, 11.3U/mL phytase activity in I91 and 9.4U/mL alkaline phosphatase activity in SM1 were also obtained. Most isolates showed multiple PGP traits which resulted in significant plant growth promotion of chick pea plants. Present study shows repression of P solubilization by succinate for various bacterial groups which might be one of the reasons why phosphate solubilizing bacteria which perform well in vitro often fail in vivo. Studying this repression mechanism might be critical in understanding the in vivo efficacy.

Extractive fermentation for enhanced production of alkaline phosphatase from Bacillus licheniformis MTCC 1483 using aqueous two-phase systems

A study was made to find out maximum partitioning of Bacillus licheniformis alkaline phosphatase in different ATPSs composed of different molecular weight of PEG X (X=2000, 4000, 6000) with salts (magnesium sulphate, sodium sulphate, sodium citrate) and polymers (dextran 40, dextran T500). Physicochemical factors such as effect of system pH, system temperature and production media were evaluated for partitioning of alkaline phosphatase. PEG 4000 [9.0% (w/v)] and dextran T500 [9.6% (w/v)] were selected as most suitable system components for alkaline phosphatase production by B. licheniformis based on greater partition coefficient (k=5.23). The two-phase system produced fewer enzymes than the homogeneous fermentation (control) in early stage of fermentation, but after 72 h the enzyme produced in the control system was less than that in the ATPS. Total alkaline phosphatase yield in ATPS fermentation was 3907.01 U/ml and in homogeneous fermentation 2856.50 U/ml.

Purification and characterization of two extracellular alkaline phosphatases from a psychrophilic arthrobacter isolate

Two extracellular, heat-labile alkaline phosphatases were purified from a psychrophilic Arthrobacter isolate, D10. The enzymes were active over different pH ranges, used distinct substrates, and had different kinetic properties. Each enzyme reacted specifically to its own antibody during immunoblot analysis. One had both monophosphatase and diesterase activities.

Novel ultramicrobacterial isolates from a deep Greenland ice core represent a proposed new species, Chryseobacterium greenlandense sp. nov

Three novel orange, ultramicrobacterial isolates, UMB10, UMB14, and UMB34(T) were isolated from enrichment cultures inoculated with a melted 3,043 m deep Greenland ice core sample. Phylogenetic analysis of the 16S rRNA gene sequences indicated that the isolates belonged to a single species within the genus Chryseobacterium. They were most closely related to Chryseobacterium aquaticum (99.3%), Chryseobacterium soli (97.1%), and Chryseobacterium soldanellicola (96.9%). Genomic hybridization showed low levels of relatedness between UMB34(T) and C. aquaticum and C. soldanellicola (19-30%) and C. soli and Chryseobacterium jejuense (45-56%). Comparative genomic fingerprinting analysis using the enterobacterial repetitive intergenic consensus (ERIC) sequence showed nearly identical banding patterns for the three isolates and these patterns were distinct from those of C. aquaticum, C. soldanellicola, C. soli, and C. jejuense. The cells were short rods, lacked flagella, had cell volumes of <0.1 mum(3), formed buds and smaller protrusions (blebs), produced copious extracellular material and a flexirubin type pigment. UMB34(T) produced acids from carbohydrates and utilized glucose and maltose although it did not assimilate mannose. The DNA G + C was 39.6-41.6 mol%. Based on the differences from validly named Chryseobacterium species, it was concluded that these isolates represent a new species for which the name, Chryseobacterium greenlandense is proposed. The type strain is UMB34(T) (=CIP 110007T = NRRL B-59357).

Effects of replacing active site residues in a cold-active alkaline phosphatase with those found in its mesophilic counterpart from Escherichia coli

Alkaline phosphatase (AP) from a North Atlantic marine Vibrio bacterium was previously characterized as being kinetically cold-adapted. It is still unknown whether its characteristics originate locally in the active site or are linked to more general structural factors. There are three metal-binding sites in the active site of APs, and all three metal ions participate in catalysis. The amino acid residues that bind the two zinc ions most commonly present are conserved in all known APs. In contrast, two of the residues that bind the third metal ion (numbered 153 and 328 in Escherichia coli AP) are different in various APs. This may explain their different catalytic efficiencies, as the Mg2+ most often present there is important for both structural stability and the reaction mechanism. We have mutated these key residues to the corresponding residues in E. coli AP to obtain the double mutant Asp116/Lys274, and both single mutants. All these mutants displayed reduced substrate affinity and lower overall reaction rates. The Lys274 and Asp116/Lys274 mutants also displayed an increase in global heat stability, which may be due to the formation of a stabilizing salt bridge. Overall, the results show that a single amino acid substitution in the active site is sufficient to alter the structural stability of the cold-active Vibrio AP both locally and globally, and this influences kinetic properties.

Extracytoplasmic storage as the nickel resistance mechanism in a natural isolate of Pseudomonas putida S4

Metal resistances in microbes are important to study not only to understand metal homeostasis but also to use such organisms further in environmental bioremediation. Nickel (Ni2+) is an important micronutrient, which at higher concentration becomes toxic. Many Ni2+-resistant organisms are known, which resist metal by active efflux. Pseudomonas putida S4, a natural isolate from India, is reported to show a multi-metal resistance profile. In the present study, the Ni2+-resistance mechanism in strain S4 was examined. Wild-type cells gradually accumulated Ni2+ but kept it preferentially in the periplasmic space in a bound form. In Ni2+-sensitive mutants, periplasmic storage was disturbed and more metal accumulated cytoplasmically, producing toxicity. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis of periplasmic proteins revealed a band of approximately 18 kDa, which appeared only in Ni2+-exposed wild-type cells, and which was absent from cells not exposed to Ni2+ as well as from Ni2+-sensitive mutants. On the basis of these observations, we propose a Ni2+-resistance mechanism in P. putida S4 based on sequestration of metal in the periplasmic space. This is the first study of sequestration-based Ni2+ resistance.

Characterization of a thermostable alkaline phosphatase from a novel species Thermus yunnanensis sp. nov. and investigation of its cobalt activation at high temperature

A thermostable alkaline phosphatase with high specific activity and thermal resistance was purified from a novel species of Thermus sp. named as Thermus yunnanensis sp. nov. The enzyme contains a single peptide with a molecular mass of about 52 kDa on SDS-PAGE analysis and appears to be a homodimer in solution with the molecular mass of 104 kDa. The optimal pH and temperature for its activities are pH 8.0-10.0 and 70-80 degrees C, respectively. The catalytic activities of the enzyme are metal ion dependent, and Mg2+, Zn2+ and Co2+ are the main activators. Among these, Co2+ is the most active stimulator and has unique activation effect at high temperature. Metal binding analysis showed the binding of Mg2+ at the metal binding site was easy to loss in the thermoinactivation, and Co2+ was apt to bind at that site and kept the favorable configuration of catalysis, which would result high activation in the incubation with Co2+ at high temperature. According to this study, a model was proposed for the explanation of the activation and the results of actual experiments demonstrated the validity of the model.

Rhodoglobus vestalii gen. nov., sp. nov., a novel psychrophilic organism isolated from an Antarctic Dry Valley lake

A novel, psychrophilic, gram-positive bacterium (designated strain LV3T) from a lake near the McMurdo Ice Shelf, Antarctica, has been isolated and characterized. This organism formed red-pigmented colonies, had an optimal growth temperature of 18 degrees C and grew on a variety of media between -2 and 21 degrees C. Scanning electron micrographs of strain LV3T that showed small rods with unusual bulbous protuberances during all phases of growth were of particular interest. The G + C content of the genomic DNA was approximately 62 mol%. The cell walls contained ornithine as the diamino acid. The major fatty acids were anteiso-C15:0, iso-C16:0 and anteiso-C17:0. Cells grown at -2 degrees C contained significant amounts of anteiso-C15:1. The major menaquinones found in strain LV3T were MK-11 and MK-12. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain LV3T was a member of the family Microbacteriaceae and related to, but distinct from, organisms belonging to the genera Agreia, Leifsonia and Subtercola. In addition, alignments of 16S rRNA sequences showed that the sequence of strain LV3T contained a 13 bp insertion that was found in only a few related sequences. Based on the low growth temperature, unusual cell shape, distinct 16S rRNA gene sequence and structure and cell-wall amino acid and menaquinone compositions, Rhodoglobus vestalii gen. nov., sp. nov. is proposed, with the type strain LV3T (= ATCC BAA-534T = CIP 107482T).

Heat-labile bacterial alkaline phosphatase from a marine Vibrio sp

Psychrophilic organisms have successfully adapted to various low-temperature environments such as cold ocean waters. Catalysts with increased catalytic efficiencies are produced, generally at the expense of thermal stability due to fewer non-covalent stabilizing interactions. A marine bacterial strain producing a particularly heat-labile alkaline phosphatase was selected from a total of 232 strains isolated from North-Atlantic coastal waters. From partial 16S rRNA sequences the strain was characterized as a Vibrio sp. An alkaline phosphatase was purified 151-fold with 54% yield from the culture medium using a single step affinity chromatography procedure on agarose-linked L-histidyldiazobenzylphosphonic acid. The active enzyme was a 55 +/- 6 kDa monomer. The enzyme had optimal activity at pH 10 and was strikingly heat-labile with a half-life of 6 min at 40 degrees C and 30 min at 32 degrees C. This enzyme from Vibrio sp. had a higher turnover number (k(cat)) and higher apparent Michaelis-Menten factor (K(m)) than the enzyme from Escherichia coli, a clear-indication of cold-adaptation. Inorganic phosphate was a competitive inhibitor with a relatively high K(i) value of 1.7 mM. Low affinity for phosphate may contribute to higher turnover rates due to more facile release of product.

Optimization for beta-mannanase production of a psychrophilic bacterium, Flavobacterium sp

We found that a psychrophilic bacterium, Flavobacterium sp., characterized in this study, has a beta-mannanase (EC 3.2.1.78) activity in the culture medium. The mannanase activity was the highest in the culture medium, containing 1.0% (w/v) guar gum (as a carbon source), 0.3% (NH4)2SO4 (as a nitrogen source), and 0.06% (w/v) yeast extract, of five-days cultivation at 4 degrees C. No mannanase activity was found in the medium containing a monosaccharide or a disaccharide as a carbon source, although the psychrophile could use them. The enzyme activity was found only when the bacterium was cultured in the medium containing a polysaccharide. The enzyme preparation showed a single activity band on a washed gel of SDS-PAGE. The optimal temperature for the enzyme activity was 35 degrees C. When the reaction was done at 10 degrees C, the enzyme showed 25% of the optimal activity. The beta-mannanase preparation efficiently hydrolyzed guar gum, locust bean gum, and glucomannan as well as beta-mannan.