Thermostable enzymes

Accelerated molecular dynamics study to compare the thermostability of Bacillus licheniformis and Aspergillus niger α-amylase

The thermostability of enzymes plays a significant role in the starch hydrolysis process in the industry. The structural difference between thermostable Bacillus licheniformis α-amylase (BLA) and thermolabile Aspergillus niger α-amylase (ANA) is interesting to be explored. This work aimed to study the thermostability-determining factor of BLA as compared to a non-thermostable enzyme, ANA, using molecular dynamics (MD) simulation at a high temperature. A 100 ns of classical MD, which was followed by 200 ns accelerated MD was conducted to explore the conformational changes of the enzyme. It is revealed that the intramolecular interactions through salt bridge interactions and the presence of calcium ions dominates the stability effect of BLA, despite the absence of a disulfide bond in the structure. These results should be useful in designing a thermostable enzyme that can be used in industrial processes.Communicated by Ramaswamy H. Sarma.

The methanogen core and pangenome: conservation and variability across biology's growth temperature extremes

Temperature is a key variable in biological processes. However, a complete understanding of biological temperature adaptation is lacking, in part because of the unique constraints among different evolutionary lineages and physiological groups. Here we compared the genomes of cultivated psychrotolerant and thermotolerant methanogens, which are physiologically related and span growth temperatures from -2.5°C to 122°C. Despite being phylogenetically distributed amongst three phyla in the archaea, the genomic core of cultivated methanogens comprises about one-third of a given genome, while the genome fraction shared by any two organisms decreases with increasing phylogenetic distance between them. Increased methanogenic growth temperature is associated with reduced genome size, and thermotolerant organisms-which are distributed across the archaeal tree-have larger core genome fractions, suggesting that genome size is governed by temperature rather than phylogeny. Thermotolerant methanogens are enriched in metal and other transporters, and psychrotolerant methanogens are enriched in proteins related to structure and motility. Observed amino acid compositional differences between temperature groups include proteome charge, polarity and unfolding entropy. Our results suggest that in the methanogens, shared physiology maintains a large, conserved genomic core even across large phylogenetic distances and biology's temperature extremes.

Enzyme Kinetics Features of the Representative Engineered Recombinants of Chondroitinase ABC I

Chondroitinase ABC I (cABC I) from Proteus vulgaris is an important enzyme in medicinal biotechnology due to its ability to help axon regeneration after spinal cord injury. Its practical application involves solving several problems at the molecular and cellular levels. Structurally, most residues at the C-terminal domain of cABC I are arranged as organized strands, and only a small fraction of residues have helical conformation. The structural and functional features of modified residues on two specific helix fragments have previously been reported. The single mutant M889K has been combined with L679S and L679D mutants to make enzyme variants containing simultaneously modified helix. Here, the pH stability and temperature-based analysis of the transition state structure for the catalysis reaction were investigated. We found that double mutant L679D/M889K is the better choice to use in physiological conditions due to its higher pH stability at physiological pH as well as its different optimum temperature as compared with the (wild-type) WT protein. According to Arrhenius's analysis, the values of the Gibbs free energy of the transition state (∆G^#) are not changed upon mutation. However, the relative contribution and absolute values of the enthalpy and entropy change to the total value of ∆G^#, varied between the WT and mutants.

Diversity and distribution of thermophilic microorganisms and their applications in biotechnology

Hot springs ecosystem is the most ancient continuously inhabited ecosystem on earth which harbors diverse thermophilic bacteria and archaea distributed worldwide. Life in extreme environments is very challenging so there is a great potential biological dark matter and their adaptation to harsh environments eventually producing thermostable enzymes which are very vital for the welfare of mankind. There is an enormous need for a new generation of stable enzymes that can endure harsh conditions in industrial processes and can either substitute or complement conventional chemical processes. Here, we review at the variety and distribution of thermophilic microbes, as well as the different thermostable enzymes that help them survive at high temperatures, such as proteases, amylases, lipases, cellulases, pullulanase, xylanases, and DNA polymerases, as well as their special properties, such as high-temperature stability. We have documented the novel isolated thermophilic and hyperthermophilic microorganisms, as well as the discovery of their enzymes, demonstrating their immense potential in the scientific community and in industry.

Experimental and mathematical modeling approaches for biocatalytic post-consumer poly(ethylene terephthalate) hydrolysis

The environmental impact arising from poly(ethylene terephthalate) (PET) waste is notable worldwide. Enzymatic PET hydrolysis can provide chemicals that serve as intermediates for value-added product synthesis and savings in the resources. In the present work, some reaction parameters were evaluated on the hydrolysis of post-consumer PET (PC-PET) using a cutinase from Humicola insolens (HiC). The increase in PC-PET specific area leads to an 8.5-fold increase of the initial enzymatic hydrolysis rate (from 0.2 to 1.7 mmol L^-1 h^-1), showing that this parameter plays a crucial role in PET hydrolysis reaction. The effect of HiC concentration was investigated, and the enzymatic PC-PET hydrolysis kinetic parameters were estimated based on three different mathematical models describing heterogeneous biocatalysis. The model that best fits the experimental data (R² = 0.981) indicated 1.68 mg_protein mL^-1 as a maximum value of the enzyme concentration to optimize the reaction rate. The HiC thermal stability was evaluated, considering that it is a key parameter for its efficient use in PET degradation. The enzyme half-life was shown to be 110 h at 70 ºC and pH 7.0, which outperforms most of the known enzymes displaying PET hydrolysis activity. The results evidence that HiC is a very promising biocatalyst for efficient PET depolymerization.

Aspartic protease-pepstatin A interactions: Structural insights on the thermal inactivation mechanism

Aspartic proteases are the targets for structure-based drug design for their role in physiological processes and pharmaceutical applications. Structural insights into the thermal inactivation mechanism of an aspartic protease in presence and absence of bound pepstatin A have been obtained by kinetics of thermal inactivation, CD, fluorescence spectroscopy and molecular dynamic simulations. The irreversible thermal inactivation of the aspartic protease comprised of loss of tertiary and secondary structures succeeded by the loss of activity, autolysis and aggregation The enthalpy and entropy of thermal inactivation of the enzyme in presence of pepstatin A increased from 81.2 to 148.5 kcal mol^-1, and from 179 to 359 kcal mol^-1 K^-1 respectively. Pepstatin A shifted the mid-point of thermal inactivation of the protease from 58 °C to 77 °C. The association constant (K) for pepstatin A with aspartic protease was 2.5 ± 0.3 × 10 ⁵ M^-1 and ΔG^o value was -8.3 kcal mol^-1. Molecular dynamic simulation studies were able to delineate the role of pepstatin A in stabilizing backbone conformation and side chain interactions. In the Cα-backbone, the short helical segments and the conserved glycines were part of the most unstable segments of the protein. Understanding the mechanism of thermal inactivation has the potential to develop re-engineered thermostable proteases.

Effect of Cultural Conditions on Protease Production by a Thermophilic Geobacillus thermoglucosidasius SKF4 Isolated from Sungai Klah Hot Spring Park, Malaysia

Major progress in the fields of agriculture, industry, and biotechnology over the years has influenced the quest for a potent microorganism with favorable properties to be used in scientific research and industry. This study intended to isolate a new thermophilic-protease-producing bacterium and evaluate its growth and protease production under cultural conditions. Protease producing bacteria were successfully isolated from Sungai Klah Hot Spring Park in Perak, Malaysia, and coded as SKF4; they were promising protease producers. Based on microscopic, morphological, and 16S rRNA gene analysis, isolate SKF4 was identified as Geobacillus thermoglucosidasius SKF4. The process of isolating SKF4 to grow and produce proteases under different cultural conditions, including temperature, pH, NaCl concentration, carbon and nitrogen sources, and incubation time, was explored. The optimum cultural conditions observed for growth and protease production were at 60 to 65 °C of temperature, pH 7 to 8, and under 1% NaCl concentration. Further, the use of casein and yeast extract as the nitrogen sources, and sucrose and fructose as the carbon sources enhanced the growth and protease production of isolate SKF4. Meanwhile, isolate SKF4 reached maximum growth and protease production at 24 h of incubation time. The results of this study revealed a new potent strain of thermophilic bacterium isolated from Sungai Klah Hot Spring Park in Perak, Malaysia for the first time. The high production of thermostable protease enzyme by G. thermoglucosidasius SKF4 highlighted the promising properties of this bacterium for industrial and biotechnological applications.

An evolution-based designing and characterization of mutants of cyclomaltodextrinase: Molecular modeling and spectroscopic studies

Cyclomaltodextrinase (CDase) is a member of the alpha-amylase family GH13, the subfamily GH13_20. In addition to CDase and neopullulanase, this subfamily also contains maltogenic amylase. They have common structural features, but different substrate specificity. In current work, a combination of bioinformatics and experimental tools were used for designing and constructions of single and double mutants of a new variant of CDase from Anoxybacillus flavithermus. Considering the evolutionary variable positions 123 and 127 at the dimer interface of subunits in the alpha-amylase family, these positions in CDase were modified and three mutants, including A123V, C127Q and A123V/C127Q were constructed. The tertiary structure of WT and mutants were made with the MODELLER program, and the phylogenetic tree of homologous protein sequences was built with selected programs in Phylip package. Enzyme kinetic studies revealed that the catalytic efficiency of mutants, especially double one, is lower than the WT enzyme. Heat-induced denaturation experiments were monitored by measuring the UV/Vis signal at 280 nm, and it was found that WT protein is structurally more stable at 25 °C. However, it is more susceptible to changes in temperature compared to the double mutant. It was concluded that the positions 123 and 127 at the dimeric interface of CDase, not only could affect the conformational stability; but also; the catalytic properties of the enzyme by setting up the active site configuration in the dimeric state.

Purification, Characterization and Thermodynamic Assessment of an Alkaline Protease by Geotrichum Candidum of Dairy Origin

Background

Alkaline proteases is the important group of enzymes having numerous industrial applications including dairy food formulations.

Objectives

The current study deals with the purification and characterization of an alkaline serine protease produced by Geotrichum candidum QAUGC01, isolated from indigenous fermented milk product, Dahi.

Material and Methods

In total twelve G. candidum strains were screened for their proteolytic activity by using standard protease assay. The protease production from G. candidum QAUGC01 was optimized by varying physio-chemical conditions. The protease was purified by using two-step method: ammonium sulfate precipitation and gel filtration chromatography. Protease was further characterized by studying various parameter like temperature, pH, modulators, metal ions and organic solvent. A thermodynamic study was also carried out to explore the half-life of protease.

Results

The G. candidum grew profusely at 25 °C and at an initial pH of 4.0 for 72 h of incubation producing 26.21 U/ml maximum extracellular protease. Protease revealed that V_max and K_m was 26.25 U.ml^-1.min^-1 and 0.05 mg.mL^-1, respectively using casein as substrate. The enzyme was stable at a temperature range (25-45 °C) and pH (8-9). Residual enzyme activity was strongly inhibited in the presence of PMSF (7.5%). The protease could hydrolyze proteinaceous substrates, casein (98%) and BSA (95%). The thermodynamic studies explored that the half-life of the enzyme that was 106.62 min, 38.72 min and 15.71 min at 50, 60 and 70 °C, respectively.

Conclusions

Purified protease from G. candidum GCQAU01 is an ideal candidate for industrial application.

Amylase and Xylanase from Edible Fungus Neurospora intermedia: Production and Characterization

Integrated enzyme production in the biorefinery can significantly reduce the cost of the entire process. The purpose of the present study is to evaluate the production of two hydrolyzing enzymes (amylase and xylanase) by an edible fungus used in the biorefinery, Neurospora intermedia. The enzyme production was explored through submerged fermentation of synthetic media and a wheat-based waste stream (thin stillage and wheat bran). The influence of a nitrogen source on N. intermedia was investigated and a combination of NaNO₃ and yeast extract has been identified as the best nitrogen source for extracellular enzyme production. N. intermedia enzymes showed maximum activity at 65 °C and pH around 5. Under these conditions, the maximum velocity of amylase and xylanase for starch and xylan hydrolysis was found to be 3.25 U mL⁻¹ and 14.77 U mL⁻¹, respectively. Cultivation of N. intermedia in thin stillage and wheat bran medium resulted in relatively high amylase (8.86 ± 0.41 U mL⁻¹, 4.68 ± 0.23) and xylanase (5.48 ± 0.21, 2.58 ± 0.07 U mL⁻¹) production, respectively, which makes this fungus promising for enzyme production through a wheat-based biorefinery.

Solid-phase synthesis of protein-polymers on reversible immobilization supports

Facile automated biomacromolecule synthesis is at the heart of blending synthetic and biologic worlds. Full access to abiotic/biotic synthetic diversity first occurred when chemistry was developed to grow nucleic acids and peptides from reversibly immobilized precursors. Protein-polymer conjugates, however, have always been synthesized in solution in multi-step, multi-day processes that couple innovative chemistry with challenging purification. Here we report the generation of protein-polymer hybrids synthesized by protein-ATRP on reversible immobilization supports (PARIS). We utilized modified agarose beads to covalently and reversibly couple to proteins in amino-specific reactions. We then modified reversibly immobilized proteins with protein-reactive ATRP initiators and, after ATRP, we released and analyzed the protein polymers. The activity and stability of PARIS-synthesized and solution-synthesized conjugates demonstrated that PARIS was an effective, rapid, and simple method to generate protein-polymer conjugates. Automation of PARIS significantly reduced synthesis/purification timelines, thereby opening a path to changing how to generate protein-polymer conjugates.

Microinjection for the ex Vivo Modification of Cells with Artificial Organelles

Microinjection is extensively used across fields to deliver material intracellularly. Here we address the fundamental aspects of introducing exogenous organelles into cells to endow them with artificial functions. Nanocarriers encapsulating biologically active cargo or extreme intraluminal pH were injected directly into the cytosol of cells, where they bypassed subcellular processing pathways and remained intact for several days. Nanocarriers' size was found to dictate their intracellular distribution pattern upon injection, with larger vesicles adopting polarized agglomerated distributions and smaller colloids spreading evenly in the cytosol. This in turn determined the symmetry or asymmetry of their dilution following cell division, ultimately affecting the intracellular dose at a cell population level. As an example of microinjection's applicability, a cell type relevant for cell-based therapies (dendritic cells) was injected with vesicles, and its migratory properties were studied in a co-culture system mimicking lymphatic capillaries.

A multi-tolerant low molecular weight mannanase from Bacillus sp. CSB39 and its compatibility as an industrial biocatalyst

Bacillus sp. CSB39, isolated from popular traditional Korean food (Kimchi), produced a low molecular weight, thermostable mannanase (MnCSB39); 571.14U/mL using locust bean gum galactomannan as a major substrate. It was purified to homogeneity using a simple and effective two-step purification strategy, Sepharose CL-6B and DEAE Sepharose Fast Flow, which resulted in 25.47% yield and 19.32-fold purity. The surfactant-, NaCl-, urea-, and protease-tolerant monomeric protein had a mass of ∼30kDa as analyzed by SDS-PAGE and galactomannan zymography. MnCSB39 was found to have optimal activity at pH 7.5 and temperature of 70°C. The enzyme showed ˃55% activity at 5.0-15% (w/v) NaCl, and ˃93% of the initial activity after incubation at 37°C for 60min. Trypsin and proteinase K had no effect on MnCBS39. The enzyme showed ˃80% activity in up to 3M urea. The N-terminal amino acid sequence, ALKGDGX, did not show identity with reported mannanases, which suggests the novelty of our enzyme. Activation energy for galactomannan hydrolysis was 26.85kJmol(-1) with a Kcat of 142.58×10(4)s(-1). MnCSB39 had Km and Vmax values of 0.082mg/mL and 1099±1.0Umg(-1), respectively. Thermodynamic parameters such as ΔH, ΔG, ΔS, Q10, ΔGE-S, and ΔGE-T supported the spontaneous formation of products and the high hydrolytic efficiency and feasibility of the enzymatic reaction, which strengthen its novelty. MnCSB39 activity was affected by metal ions, modulators, chelators, and detergents. Mannobiose was the principal end-product of hydrolysis. Bacillus subtilis CSB39 produced a maximum of 1524.44U mannanase from solid state fermentation of 1g wheat bran. MnCSB39 was simple to purify, was active at a wide pH and temperature range, multi-stress tolerant and catalyzes a thermodynamically possible reaction, characteristics that suggests its suitability for application as an industrial biocatalyst.

Immobilization of Clostridium cellulolyticum D-psicose 3-epimerase on artificial oil bodies

The rare sugar D-psicose possesses several fundamental biological functions. D-Psicose 3-epimerase from Clostridium cellulolyticum (CC-DPEase) has considerable potential for use in D-psicose production. In this study, CC-DPEase was fused to the N terminus of oleosin, a unique structural protein of seed oil bodies and was overexpressed in Escherichia coli as a CC-DPEase-oleosin fusion protein. After reconstitution into artificial oil bodies (AOBs), refolding, purification, and immobilization of the active CC-DPEase were simultaneously accomplished. Immobilization of CC-DPEase on AOB increased the optimal temperature but decreased the optimal pH of the enzyme activity. Furthermore, the AOB-immobilized CC-DPEase had a thermal stability and a bioconversion rate similar to those of the free-form enzyme and retained >50% of its initial activity after five cycles of enzyme use. Thus, AOB-immobilized CC-DPEase has potential application in the production of d-psicose at a lower cost than the free-form enzyme.

Characterization of xylan utilization and discovery of a new endoxylanase in Thermoanaerobacterium saccharolyticum through targeted gene deletions

The economical production of fuels and commodity chemicals from lignocellulose requires the utilization of both the cellulose and hemicellulose fractions. Xylanase enzymes allow greater utilization of hemicellulose while also increasing cellulose hydrolysis. Recent metabolic engineering efforts have resulted in a strain of Thermoanaerobacterium saccharolyticum that can convert C(5) and C(6) sugars, as well as insoluble xylan, into ethanol at high yield. To better understand the process of xylan solubilization in this organism, a series of targeted deletions were constructed in the homoethanologenic T. saccharolyticum strain M0355 to characterize xylan hydrolysis and xylose utilization in this organism. While the deletion of β-xylosidase xylD slowed the growth of T. saccharolyticum on birchwood xylan and led to an accumulation of short-chain xylo-oligomers, no other single deletion, including the deletion of the previously characterized endoxylanase XynA, had a phenotype distinct from that of the wild type. This result indicates a multiplicity of xylanase enzymes which facilitate xylan degradation in T. saccharolyticum. Growth on xylan was prevented only when a previously uncharacterized endoxylanase encoded by xynC was also deleted in conjunction with xynA. Sequence analysis of xynC indicates that this enzyme, a low-molecular-weight endoxylanase with homology to glycoside hydrolase family 11 enzymes, is secreted yet untethered to the cell wall. Together, these observations expand our understanding of the enzymatic basis of xylan hydrolysis by T. saccharolyticum.

Catalytic and thermodynamic characterization of endoglucanase (CMCase) from Aspergillus oryzae cmc-1

Monomeric extracellular endoglucanase (25 kDa) of transgenic koji (Aspergillus oryzae cmc-1) produced under submerged growth condition (7.5 U mg(-1) protein) was purified to homogeneity level by ammonium sulfate precipitation and various column chromatography on fast protein liquid chromatography system. Activation energy for carboxymethylcellulose (CMC) hydrolysis was 3.32 kJ mol(-1) at optimum temperature (55 degrees C), and its temperature quotient (Q (10)) was 1.0. The enzyme was stable over a pH range of 4.1-5.3 and gave maximum activity at pH 4.4. V (max) for CMC hydrolysis was 854 U mg(-1) protein and K (m) was 20 mg CMC ml(-1). The turnover (k (cat)) was 356 s(-1). The pK (a1) and pK (a2) of ionisable groups of active site controlling V (max) were 3.9 and 6.25, respectively. Thermodynamic parameters for CMC hydrolysis were as follows: DeltaH* = 0.59 kJ mol(-1), DeltaG* = 64.57 kJ mol(-1) and DeltaS* = -195.05 J mol(-1) K(-1), respectively. Activation energy for irreversible inactivation 'E (a(d))' of the endoglucanase was 378 kJ mol(-1), whereas enthalpy (DeltaH*), Gibbs free energy (DeltaG*) and entropy (DeltaS*) of activation at 44 degrees C were 375.36 kJ mol(-1), 111.36 kJ mol(-1) and 833.06 J mol(-1) K(-1), respectively.

Effect of aniline coupling on kinetic and thermodynamic properties of Fusarium solani glucoamylase

Purified glucoamylase (GA) from Fusarium solani was chemically modified by cross-linking with aniline hydrochloride in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) for 1 [aniline-coupled glucoamylase-1 (ACG-1)], 7 (ACG-7), and 13 min (ACG-13). The aniline coupling of GA had a profound enhancing effect on temperature, pH optima, and pK (a)'s of active site residues. The specificity constants (K (cat)/K (m)) of native, ACG-1, ACG-7, and ACG-13 were 136, 244, 262, and 208 at 55 degrees C for starch, respectively. The enthalpy of activation (DeltaH*) and free energy of activation (DeltaG*) for soluble starch hydrolysis were lower for the chemically modified forms compared to native GA. Proteolysis of ACGs by alpha-chymotrypsin and subtilisin resulted in activation.

Characterization of Active Lentinula edodes Glucoamylase Expressed and Secreted by Saccharomyces cerevisiae

The gene encoding Lentinula edodes glucoamylase (GLA) was cloned into Saccharomyces cerevisiae, expressed constitutively and secreted in an active form. The enzyme was purified to homogeneity by (NH4)2SO4 fractionation, anion exchange and affinity chromatography. The protein had a correct N-terminal sequence of WAQSSVIDAYVAS, indicating that the signal peptide was efficiently cleaved. The recombinant enzyme was glycosylated with a 2.4% carbohydrate content. It had a pH optimum of 4.6 and a pH 3.4-6.4 stability range. The temperature optimum was 50 degrees C with stability <or=50 degrees C. The enzyme showed considerable loss of activity when incubated with glucose (44%), glucosamine (68%), galactose (22%), and xylose (64%). The addition of Mn++ activated the enzyme by 45%, while Li+, Zn++, Mg++, Cu+, Ca++, and EDTA had no effect. The enzyme hydrolyzed amylopectin at rates 1.5 and 8.0 times that of soluble starch and amylose, respectively. Soluble starch was hydrolyzed 16 and 29 times faster than wheat and corn starch granules, respectively, with the hydrolysis of starch granules using 10x the amount of GLA. Apparent Km and Vmax for soluble starch were estimated to be 3.0 mg/ml and 0.13 mg/ml/min (40 degrees C, pH 5.3), with an apparent kcat of 2.9 x 10(5) min(-1).

The enzymes from extreme thermophiles: bacterial sources, thermostabilities and industrial relevance

This review on enzymes from extreme thermophiles (optimum growth temperature greater than 65 degrees C) concentrates on their characteristics, especially thermostabilities, and their commercial applicability. The enzymes are considered in general terms first, with comments on denaturation, stabilization and industrial processes. Discussion of the enzymes subsequently proceeds in order of their E.C. classification: oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases. The ramifications of cloned enzymes from extreme thermophiles are also discussed.

Does the increased hydrophobicity of the interior and hydrophilicity of the exterior of an enzyme structure reflect its increased thermostability?

The values of hydrophobicity of internal and external elements of the secondary structure of three Bacillus alpha-amylase (beta alpha)8 barrel domains have been calculated in order to investigate whether there is some correlation between the values and the enzyme stability. All the values have been referred to the number of amino acids in the given beta-sheet or alpha-helix to eliminate the differences caused by non-equal length of the sheet or helix. Hydrophobicity units obtained have been averaged according to the number of internal (all beta-strands and helix alpha 7) and external (helices alpha 1-alpha 6 and alpha 8) elements of secondary structure of the alpha-amylase (beta alpha)8 barrel. The averaged hydrophobicity units have been found to correlate with the thermal stability of the three Bacillus alpha-amylases in terms of the increased hydrophobicity of the interior as well as the increased hydrophilicity of the exterior of the (beta alpha)8 barrel domain for the alpha-amylase with increased thermostability.

Thermostable mutants of kanamycin nucleotidyltransferase are also more stable to proteinase K, urea, detergents, and water-miscible organic solvents

A series of variants of kanamycin nucleotidyltransferase (KNTase), isolated previously on the basis of enhanced thermostability by cloning and selection for enzymatic activity in the thermophile Bacillus stearothermophilus, was used to systematically test the hypothesis that thermostable enzymes would also be more resistant to other forms of protein denaturation. The purified KNTases were treated with proteinase K or assayed at 37 degrees C in the presence of urea, N-lauroylsarcosine, Triton X-100, tetrahydrofuran, ethanol, or dimethylformamide. With all these agents, the KNTases displayed increasing resistance to denaturation in the order: wild type, mutant TK9 (with a Thr130-->Lys substitution), TK1 (Asp80-->Tyr), and TK101 (both substitutions). This is the same order in which their thermostability increases, indicating that the structural mechanism(s) whereby the mutations yield enhanced resistance to heat denaturation also yield stabilization towards chemical forms of enzymatic inactivation. These results suggest that selection in thermophiles is a useful method to obtain enzyme variants with increased overall stability, even at nonthermophilic temperatures.

Use of monoclonal antibodies to demonstrate different sites with different functional characteristics in a bacterial lipase from Pseudomonas aeruginosa YS-7

Structural and functional features of the extracellular lipase from the low-water-tolerant bacterium Pseudomonas aeruginosa YS-7 were studied immunochemically with the aid of monoclonal antibodies (MAbs) raised against the enzyme. Fourteen different MAbs were obtained, verified as immunoglobulin G types, and characterized by their interaction with the enzyme in relation to (i) inhibition of activity of free enzyme, (ii) inhibition of activity of adsorbed enzyme, (iii) interaction with the cell-bound enzyme, and (iv) inhibition of adherence to hexadecane droplets. Four of the MAbs exhibiting the highest binding constants (Kapp greater than 10(8) M-1) were selected for further study of the lipase. Their binding to the enzyme was assayed by means of adapted enzyme-linked immunosorbent assay techniques. Use of these MAbs in single or dual binding procedures made it possible to reveal several distinct sites on the lipase macromolecule. Two of these are functional sites, one for hydrophobic adhesion (binds MAb 5) and the other (binds MAb 1) for implementation of its hydrolytic activity. A third binding site (binds MAb 8) does not participate directly in either of the above functions. A fourth binding site (binds MAb 10) appears to be involved in the active expression of the enzyme. The cell-associated form of the lipase seems to be located on the external surface of the cells with its active site exposed. It appears to be anchored to the outer membrane of the cells by means of its hydrophobic region in a way that resembles its adherence to hydrophobic surfaces such as hexadecane droplets.

Functionally-stabilized proteins — A review

The maintenance or stabilization of protein or enzyme function is of vital importance in Biotechnology. Investigations of thermophilic organisms, studies of denaturation and the use of enzymes in organic solvents have each contributed to an understanding of protein stability. Enzymes can reliably and reproducibly be stabilized by variety of means including immobilization, use of additives, chemical modification in solution and protein engineering. Examples of each of these are discussed. With these recent advances it appears that a rational strategy for achieving a particular stabilized enzyme or protein may be within reach.

Production, Purification, and Properties of Extracellular Carboxyl Esterases from Bacillus subtilis NRRL 365

Bacillus subtilis NRRL 365 produced high extracellular carboxyl esterase activity in submerged culture media containing wheat bran, corn steep liquor, and salts. Supplementation of this medium with glucose reduced esterase activity to 37% of that in the unsupplemented control. Esterase activity was purified by ammonium sulfate fractionation, DEAE-Sephadex A-50 ion-exchange chromatography with sodium chloride gradient elution, and preparative polyacrylamide gel electrophoresis. The resultant purified components, esterases I and II, manifested single bands following silver staining of polyacrylamide gel electrophoresis gels and had final specific activities of 80 and 520 U/mg, respectively. Molecular weights for components I and II were 36,000 and 105,000 to 110,000, respectively. Esterases I and II both had a pH optimum of 8.0, with relative activities of 10 and 85%, respectively, at pH 9.0. K m s with p -nitrophenylacetate were 0.91 mM for esterase I and 0.67 mM for esterase II. In general, patterns of enzyme inhibition were similar for both components. Differences were observed in the relative activities of esterases I and II towards p -nitrophenyl esters of acetate, propionate, and butyrate; Activity ratios for components I and II were 100:94:48 and 100:36:23, respectively. The purified components did not hydrolyze long-chain triglycerides and did not manifest proteolytic activity.

Mannanase Components from Bacillus pumilus

β- d -Mannanase from Bacillus pumilus was purified into two components, A and B, which exhibited homogeneity on polyacrylamide gel electrophoresis. These components had molecular weights of 55,000 (A) and 37,000 (B); carbohydrate contents of 15.3% (A) and 7.2% (B); specific activities of 78 (A) and 1,616 (B) U/mg; pH optima of 5.5 to 6.9 (A) and 6.0 (B); and half-lives of 60 (A) and 21 (B) min at 70°C.

Hemicellulases of Bacillus species: preliminary comparative studies on production and properties of mannanases and galactanases

A range of Bacillus subtilis strains and other Bacillus species were screened for mannanase, beta-mannosidase and galactanase activities. Maximum mannanase activity, 106.2 units/ml, was produced by B. subtilis NRRL 356. beta-Mannosidase and galactanase activities from all strains were relatively low. The effect of carbon and nitrogen source on mannanase and galactanase production by B. brevis ATCC 8186, B. licheniformis ATCC 27811, B. polymyxa NRRL 842 and B. subtilis NRRL 356 was investigated. Highest mannanase production was observed in the four strains tested when the mannan substrate, locust bean gum, was used as carbon source. Induction was most dramatic in the case of B. subtilis NRRL 356 where only basal enzyme levels were produced in the presence of other carbon sources. beta-Mannosidase was induced in the four Bacillus cultures by locust bean gum. Results indicated that galactose acted as an inducer for production of galactanase. Organic and inorganic nitrogen sources resulted in induction of high mannanase titres in B. subtilis. Highest galactanase activity was produced by each organism in media containing sodium nitrate as nitrogen source. Mannanases from B. brevis, B. licheniformis, B. polymyxa and B. subtilis retained 100% residual activity after a 3 h incubation at 65 degrees C, 65 degrees C, 60 degrees C and 55 degrees C respectively. Galactanases retained more than 95% activity at 55 degrees C after 3 h. The pH optima of mannanases ranged from 6.5-6.8 whereas galactanases ranged from 5.1 in the case of B. brevis to 7.0 for B. polymyxa.