Purification and characterization of a trehalose synthase from the basidiomycete grifola frondosa

General control nonderepressible 4 activates the transcription of trehalose phosphorylase to improve trehalose production and abiotic stress tolerance in Ganoderma lucidum

Trehalose plays an important role in enhancing abiotic stress tolerance. Although studies have reported the induction of trehalose by adverse environments, the molecular mechanism underlying its induction in fungi is unclear. In fungi, the trehalose phosphorylase (TreP) catalyzes the reversible reaction of trehalose formation. Here, we found that the carbon and nitrogen metabolism integrated transcription factor, general control nonderepressible 4 (GCN4) directly binds to the promoter of TreP in Ganoderma lucidum. GCN4 up-regulates the transcription and protein levels of TreP, leading to enhanced trehalose synthase activity and trehalose accumulation. A reduced abundance of GCN4 alleviated the low-nitrogen induced increase in Trep and trehalose contents. As a result, knockdown of both GCN4 and TreP leads to a reduction in the trehalose content and growth inhibition of mycelia, especially under low-nitrogen conditions. Furthermore, in addition to nitrogen deficiency, both high temperature and drought treatments increase the transcription and protein levels of GCN4 and TreP. The GCN4 or TreP knockdown strains are hypersensitive to heat stress and drought, while exogenous trehalose treatment enhances the mycelial growth under stressful conditions. Together, our results revealed that the GCN4-TreP module promotes trehalose accumulation in response to abiotic stresses to improve the stress tolerance of G. lucidum, and highlighted the pivotal role of GCN4 in integrating metabolic adaptation to environmental stresses.

Discovery and Biotechnological Exploitation of Glycoside-Phosphorylases

Among carbohydrate active enzymes, glycoside phosphorylases (GPs) are valuable catalysts for white biotechnologies, due to their exquisite capacity to efficiently re-modulate oligo- and poly-saccharides, without the need for costly activated sugars as substrates. The reversibility of the phosphorolysis reaction, indeed, makes them attractive tools for glycodiversification. However, discovery of new GP functions is hindered by the difficulty in identifying them in sequence databases, and, rather, relies on extensive and tedious biochemical characterization studies. Nevertheless, recent advances in automated tools have led to major improvements in GP mining, activity predictions, and functional screening. Implementation of GPs into innovative in vitro and in cellulo bioproduction strategies has also made substantial advances. Herein, we propose to discuss the latest developments in the strategies employed to efficiently discover GPs and make the best use of their exceptional catalytic properties for glycoside bioproduction.

Three-Enzyme Phosphorylase Cascade for Integrated Production of Short-Chain Cellodextrins

Cellodextrins are linear β-1,4-gluco-oligosaccharides that are soluble in water up to a degree of polymerization (DP) of ≈6. Soluble cellodextrins have promising applications as nutritional ingredients. A DP-controlled, bottom-up synthesis from expedient substrates is desired for their bulk production. Here, a three-enzyme glycoside phosphorylase cascade is developed for the conversion of sucrose and glucose into short-chain (soluble) cellodextrins (DP range 3-6). The cascade reaction involves iterative β-1,4-glucosylation of glucose from α-glucose 1-phosphate (αGlc1-P) donor that is formed in situ from sucrose and phosphate. With final concentration and yield of the soluble cellodextrins set as targets for biocatalytic synthesis, three major factors of reaction efficiency are identified and partly optimized: the ratio of enzyme activity, the ratio of sucrose and glucose, and the phosphate concentration used. The efficient use of the phosphate/αGlc1-P shuttle for cellodextrin production is demonstrated and the soluble product at 40 g L^-1 is obtained under near-complete utilization of the donor substrate offered (88 mol% from 200 mm sucrose). The productivity is 16 g (L h)^-1 . Through a simple two-step route, the soluble cellodextrins are recovered from the reaction mixture in ≥95% purity and ≈92% yield. Overall, this study provides the basis for their integrated production.

Artificial Fusion of mCherry Enhances Trehalose Transferase Solubility and Stability

LeLoir glycosyltransferases are important biocatalysts for the production of glycosidic bonds in natural products, chiral building blocks, and pharmaceuticals. Trehalose transferase (TreT) is of particular interest since it catalyzes the stereo- and enantioselective α,α-(1→1) coupling of a nucleotide sugar donor and monosaccharide acceptor for the synthesis of disaccharide derivatives. Heterologously expressed thermophilic trehalose transferases were found to be intrinsically aggregation prone and are mainly expressed as catalytically active inclusion bodies in Escherichia coli To disfavor protein aggregation, the thermostable protein mCherry was explored as a fluorescent protein tag. The fusion of mCherry to trehalose transferase from Pyrobaculum yellowstonensis (PyTreT) demonstrated increased protein solubility. Chaotropic agents like guanidine or the divalent cations Mn(II), Ca(II), and Mg(II) enhanced the enzyme activity of the fusion protein. The thermodynamic equilibrium constant, K _eq, for the reversible synthesis of trehalose from glucose and a nucleotide sugar was determined in both the synthesis and hydrolysis directions utilizing UDP-glucose and ADP-glucose, respectively. UDP-glucose was shown to achieve higher conversions than ADP-glucose, highlighting the importance of the choice of nucleotide sugars for LeLoir glycosyltransferases under thermodynamic control.IMPORTANCE The heterologous expression of proteins in Escherichia coli is of great relevance for their functional and structural characterization and applications. However, the formation of insoluble inclusion bodies is observed in approximately 70% of all cases, and the subsequent effects can range from reduced soluble protein yields to a complete failure of the expression system. Here, we present an efficient methodology for the production and analysis of a thermostable, aggregation-prone trehalose transferase (TreT) from Pyrobaculum yellowstonensis via its fusion with mCherry as a thermostable fluorescent protein tag. This fusion strategy allowed for increased enzyme stability and solubility and could be applied to other (thermostable) proteins, allowing rapid visualization and quantification of the mCherry-fused protein of interest. Finally, we have demonstrated that the enzymatic synthesis of trehalose from glucose and a nucleotide sugar is reversible by approaching the thermodynamic equilibrium in both the synthesis and hydrolysis directions. Our results show that uridine establishes an equilibrium constant which is more in favor of the product trehalose than when adenosine is employed as the nucleotide under identical conditions. The influence of different nucleotides on the reaction can be generalized for all LeLoir glycosyltransferases under thermodynamic control as the position of the equilibrium depends solely on the reaction conditions and is not affected by the nature of the catalyst.

Carbohydrates protect protein against abiotic fragmentation by soil minerals

The degradation and turnover of soil organic matter is an important part of global carbon cycling and of particular importance with respect to attempts to predict the response of ecosystems to global climate change. Thus, it is important to mechanistically understand the processes by which organic matter can be degraded in the soil environment, including contact with reactive or catalytic mineral surfaces. We have characterized the outcome of the interaction of two minerals, birnessite and kaolinite, with two disaccharides, cellobiose and trehalose. These results show that birnessite reacts with and degrades the carbohydrates, while kaolinite does not. The reaction of disaccharides with birnessite produces Mn(II), indicating that degradation of the disaccharides is the result of their oxidation by birnessite. Furthermore, we find that both sugars can inhibit the degradation of a model protein by birnessite, demonstrating that the presence of one organic constituent can impact abiotic degradation of another. Therefore, both the reactivity of the mineral matrix and the presence of certain organic constituents influence the outcomes of abiotic degradation. These results suggest the possibility that microorganisms may be able to control the functionality of exoenzymes through the concomitant excretion of protective organic substances, such as those found in biofilms.

Tailoring Trehalose for Biomedical and Biotechnological Applications

Trehalose is a non-reducing sugar whose ability to stabilize biomolecules has brought about its widespread use in biological preservation applications. Trehalose is also an essential metabolite in a number of pathogens, most significantly the global pathogen Mycobacterium tuberculosis, though it is absent in humans and other mammals. Recently, there has been a surge of interest in modifying the structure of trehalose to generate analogues that have applications in biomedical research and biotechnology. Non-degradable trehalose analogues could have a number of advantages as bioprotectants and food additives. Trehalose-based imaging probes and inhibitors are already useful as research tools and may have future value in the diagnosis and treatment of tuberculosis, among other uses. Underlying the advancements made in these areas are novel synthetic methods that facilitate access to and evaluation of trehalose analogues. In this review, we focus on both aspects of the development of this class of molecules. First, we consider the chemical and chemoenzymatic methods that have been used to prepare trehalose analogues and discuss their prospects for synthesis on commercially relevant scales. Second, we describe ongoing efforts to develop and deploy detectable trehalose analogues, trehalose-based inhibitors, and non-digestible trehalose analogues. The current and potential future uses of these compounds are discussed, with an emphasis on their roles in understanding and combatting mycobacterial infection.

Gene cloning, expression, and characterization of trehalose-6-phosphate synthase from Pleurotus ostreatus

Trehalose-6-phosphate synthase (TPS; EC2.4.1.15) catalyzes the first step in trehalose synthesis, which involves transfer of glucose from uridine diphosphate glucose (UDPG) to glucose 6-phosphate (G6P) to form trehalose-6-phosphate. To determine the gene and enzymatic characteristics of TPS in Pleurotus ostreatus, we cloned and sequenced the cDNA of PoTPS1, which contains a 1665 bp open reading frame that encodes a 554-amino acid protein with a predicted molecular weight of 62.01 kDa. This gene was expressed in Escherichia coli BL21 and then the recombinant protein was purified and characterized. Results showed that the optimum pH and temperature for the recombinant PoTPS1 were 7.4 and 30 °C, respectively; the K_m value against G6P and UDPG were 0.14 and 0.17 mM, respectively, and the V_max and K_cat values were 91.86 nkat/g and 5.89 s^-1 , respectively. Trehalose content was as high as 158.88 mg g^-1 dry weight after heat treatment at 40 °C for 15 h, which was consistent with highest TPS1 activity at that time point. This result indicated that PoTPS1 was responsible for trehalose synthesis in P. ostreatus.

Central Role of the Trehalose Biosynthesis Pathway in the Pathogenesis of Human Fungal Infections: Opportunities and Challenges for Therapeutic Development

Invasive fungal infections cause significant morbidity and mortality in part due to a limited antifungal drug arsenal. One therapeutic challenge faced by clinicians is the significant host toxicity associated with antifungal drugs. Another challenge is the fungistatic mechanism of action of some drugs. Consequently, the identification of fungus-specific drug targets essential for fitness in vivo remains a significant goal of medical mycology research. The trehalose biosynthetic pathway is found in a wide variety of organisms, including human-pathogenic fungi, but not in humans. Genes encoding proteins involved in trehalose biosynthesis are mechanistically linked to the metabolism, cell wall homeostasis, stress responses, and virulence of Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus. While there are a number of pathways for trehalose production across the tree of life, the TPS/TPP (trehalose-6-phosphate synthase/trehalose-6-phosphate phosphatase) pathway is the canonical pathway found in human-pathogenic fungi. Importantly, data suggest that proteins involved in trehalose biosynthesis play other critical roles in fungal metabolism and in vivo fitness that remain to be fully elucidated. By further defining the biology and functions of trehalose and its biosynthetic pathway components in pathogenic fungi, an opportunity exists to leverage this pathway as a potent antifungal drug target. The goal of this review is to cover the known roles of this important molecule and its associated biosynthesis-encoding genes in the human-pathogenic fungi studied to date and to employ these data to critically assess the opportunities and challenges facing development of this pathway as a therapeutic target.

Integrated Approach To Producing High-Purity Trehalose from Maltose by the Yeast Yarrowia lipolytica Displaying Trehalose Synthase (TreS) on the Cell Surface

An alternative strategy that integrated enzyme production, trehalose biotransformation, and bioremoval in one bioreactor was developed in this study, thus simplifying the traditional procedures used for trehalose production. The trehalose synthase gene from a thermophilic archaea, Picrophilus torridus, was first fused to the YlPir1 anchor gene and then inserted into the genome of Yarrowia lipolytica, thus yielding an engineered yeast strain. The trehalose yield reached 73% under optimal conditions. The thermal and pH stabilities of the displayed enzyme were improved compared to those of its free form purified from recombinant Escherichia coli. After biotransformation, the glucose byproduct and residual maltose were directly fermented to ethanol by a Saccharomyces cerevisiae strain. Ethanol can be separated by distillation, and high-purity trehalose can easily be obtained from the fermentation broth. The results show that this one-pot procedure is an efficient approach to the economical production of trehalose from maltose.

Fungal spores for dispersion in space and time

Spores are an integral part of the life cycle of the gross majority of fungi. Their morphology and the mode of formation are both highly variable among the fungi, as is their resistance to stressors. The main aim for spores is to be dispersed, both in space, by various mechanisms or in time, by an extended period of dormancy. Some fungal ascospores belong to the most stress-resistant eukaryotic cells described to date. Stabilization is a process in which biomolecules and complexes thereof are protected by different types of molecules against heat, drought, or other molecules. This review discusses the most important compounds that are known to protect fungal spores and also addresses the biophysics of cell protection. It further covers the phenomena of dormancy, breaking of dormancy, and early germination. Germination is the transition from a dormant cell toward a vegetative cell and includes a number of specific changes. Finally, the applied aspects of spore biology are discussed.

Trehalose Analogues: Latest Insights in Properties and Biocatalytic Production

Trehalose (α-D-glucopyranosyl α-D-glucopyranoside) is a non-reducing sugar with unique stabilizing properties due to its symmetrical, low energy structure consisting of two 1,1-anomerically bound glucose moieties. Many applications of this beneficial sugar have been reported in the novel food (nutricals), medical, pharmaceutical and cosmetic industries. Trehalose analogues, like lactotrehalose (α-D-glucopyranosyl α-D-galactopyranoside) or galactotrehalose (α-D-galactopyranosyl α-D-galactopyranoside), offer similar benefits as trehalose, but show additional features such as prebiotic or low-calorie sweetener due to their resistance against hydrolysis during digestion. Unfortunately, large-scale chemical production processes for trehalose analogues are not readily available at the moment due to the lack of efficient synthesis methods. Most of the procedures reported in literature suffer from low yields, elevated costs and are far from environmentally friendly. "Greener" alternatives found in the biocatalysis field, including galactosidases, trehalose phosphorylases and TreT-type trehalose synthases are suggested as primary candidates for trehalose analogue production instead. Significant progress has been made in the last decade to turn these into highly efficient biocatalysts and to broaden the variety of useful donor and acceptor sugars. In this review, we aim to provide an overview of the latest insights and future perspectives in trehalose analogue chemistry, applications and production pathways with emphasis on biocatalysis.

Purification and partial biochemical-genetic characterization of trehalose 6-phosphate synthase from muscles of adult female Ascaris suum

Trehalose 6-phosphate (T6P) synthase (TPS; EC 2.4.1.15) was isolated from muscles of Ascaris suum by ammonium sulphate fractionation, ion-exchange DEAE SEPHACEL(TM) anion exchanger column chromatography and Sepharose 6B gel filtration. On sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), 265-fold purified TPS exhibited a molecular weight of 66 kDa. The optimum pH and temperature of the purified enzyme were 3.8-4.2 and 35°C, respectively. The isoelectric point (pI) of TPS was pH 5.4. The studied TPS was not absolutely substrate specific. Besides glucose 6-phosphate, the enzyme was able to use fructose 6-phosphate as an acceptor of glucose. TPS was activated by 10 mM MgCl2, 10 mM CaCl2 and 10 mM NaCl. In addition, it was inhibited by ethylenediaminetetra-acetic acid (EDTA), KCl, FeCl3 and ZnCl2. Two genes encoding TPS were isolated and sequenced from muscles of the parasite. Complete coding sequences for tps1 (JF412033.2) and tps2 (JF412034.2) were 3917 bp and 3976 bp, respectively. Translation products (AEX60788.1 and AEX60787.1) showed expression to the glucosyltransferase-GTB-type superfamily.

Identification of biofilm matrix-associated proteins from an acid mine drainage microbial community

In microbial communities, extracellular polymeric substances (EPS), also called the extracellular matrix, provide the spatial organization and structural stability during biofilm development. One of the major components of EPS is protein, but it is not clear what specific functions these proteins contribute to the extracellular matrix or to microbial physiology. To investigate this in biofilms from an extremely acidic environment, we used shotgun proteomics analyses to identify proteins associated with EPS in biofilms at two developmental stages, designated DS1 and DS2. The proteome composition of the EPS was significantly different from that of the cell fraction, with more than 80% of the cellular proteins underrepresented or undetectable in EPS. In contrast, predicted periplasmic, outer membrane, and extracellular proteins were overrepresented by 3- to 7-fold in EPS. Also, EPS proteins were more basic by ∼2 pH units on average and about half the length. When categorized by predicted function, proteins involved in motility, defense, cell envelope, and unknown functions were enriched in EPS. Chaperones, such as histone-like DNA binding protein and cold shock protein, were overrepresented in EPS. Enzymes, such as protein peptidases, disulfide-isomerases, and those associated with cell wall and polysaccharide metabolism, were also detected. Two of these enzymes, identified as β-N-acetylhexosaminidase and cellulase, were confirmed in the EPS fraction by enzymatic activity assays. Compared to the differences between EPS and cellular fractions, the relative differences in the EPS proteomes between DS1 and DS2 were smaller and consistent with expected physiological changes during biofilm development.

Arginine mediated purification of trehalose-6-phosphate synthase (TPS) from Candida utilis: Its characterization and regulation

BACKGROUND

Trehalose is the most important multifunctional, non-reducing disaccharide found in nature. It is synthesized in yeast by an enzyme complex: trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP).

METHODS

In the present study TPS is purified using a new methodology from Candida utilis cells by inclusion of 100mM l-arginine during cell lysis and in the mobile phase of high performance gel filtration liquid chromatography (HPGFLC).

RESULTS

An electrophoretically homogenous TPS that was purified was a 60 kDa protein with 22.1 fold purification having a specific activity of 2.03 U/mg. Alignment of the N-terminal sequence with TPS from Saccharomyces cerevisiae confirmed the 60 kDa protein to be TPS. Optimum activity of TPS was observed at a protein concentration of 1 μg, at a temperature of 37°C and pH 8.5. Aggregation mediated enzyme regulation was indicated. Metal cofactors, especially MnCl₂, MgCl₂ and ZnSO₄, acted as stimulators. Metal chelators like CDTA and EGTA stimulated enzyme activity. Among the four glucosyl donors, the highest V(max) and lowest K(m) values were calculated as 2.96 U/mg and 1.36 mM when adenosine di phosphate synthase (ADPG) was used as substrate. Among the glucosyl acceptors, glucose-6-phosphate (G-6-P) showed maximum activity followed by fructose-6-phosphate (F-6-P). Polyanions heparin and chondroitin sulfate were seen to stimulate TPS activity with different glucosyl donors.

GENERAL SIGNIFICANCE

Substrate specificity, V(max) and K(m) values provided an insight into an altered trehalose metabolic pathway in the C. utilis strain where ADPG is the preferred substrate rather than the usual substrate uridine diphosphaphate glucose (UDPG). The present work employs a new purification strategy as well as highlights an altered pathway in C. utilis.

Carbohydrate synthesis by disaccharide phosphorylases: reactions, catalytic mechanisms and application in the glycosciences

Disaccharide phosphorylases are glycosyltransferases (EC 2.4.1.α) of specialized carbohydrate metabolism in microorganisms. They catalyze glycosyl transfer to phosphate using a disaccharide as donor substrate. Phosphorylases for the conversion of naturally abundant disaccharides including sucrose, maltose, α,α-trehalose, cellobiose, chitobiose, and laminaribiose have been described. Structurally, these disaccharide phosphorylases are often closely related to glycoside hydrolases and transglycosidases. Mechanistically, they are categorized according the stereochemical course of the reaction catalyzed, whereby the anomeric configuration of the disaccharide donor substrate may be retained or inverted in the sugar 1-phosphate product. Glycosyl transfer with inversion is thought to occur through a single displacement-like catalytic mechanism, exemplified by the reaction coordinate of cellobiose/chitobiose phosphorylase. Reaction via configurational retention takes place through the double displacement-like mechanism employed by sucrose phosphorylase. Retaining α,α-trehalose phosphorylase (from fungi) utilizes a different catalytic strategy, perhaps best described by a direct displacement mechanism, to achieve stereochemical control in an overall retentive transformation. Disaccharide phosphorylases have recently attracted renewed interest as catalysts for synthesis of glycosides to be applied as food additives and cosmetic ingredients. Relevant examples are lacto-N-biose and glucosylglycerol whose enzymatic production was achieved on multikilogram scale. Protein engineering of phosphorylases is currently pursued in different laboratories with the aim of broadening the donor and acceptor substrate specificities of naturally existing enzyme forms, to eventually generate a toolbox of new catalysts for glycoside synthesis.

Trehalose 6-phosphate phosphatase is required for cell wall integrity and fungal virulence but not trehalose biosynthesis in the human fungal pathogen Aspergillus fumigatus

The trehalose biosynthesis pathway is critical for virulence in human and plant fungal pathogens. In this study, we tested the hypothesis that trehalose 6-phosphate phosphatase (T6PP) is required for Aspergillus fumigatus virulence. A mutant of the A. fumigatus T6PP, OrlA, displayed severe morphological defects related to asexual reproduction when grown on glucose (1%) minimal media. These defects could be rescued by addition of osmotic stabilizers, reduction in incubation temperature or increase in glucose levels (> 4%). Subsequent examination of the mutant with cell wall perturbing agents revealed a link between cell wall biosynthesis and trehalose 6-phosphate (T6P) levels. As expected, high levels of T6P accumulated in the absence of OrlA resulting in depletion of free inorganic phosphate and inhibition of hexokinase activity. Surprisingly, trehalose production persisted in the absence of OrlA. Further analyses revealed that A. fumigatus contains two trehalose phosphorylases that may be responsible for trehalose production in the absence of OrlA. Despite a normal growth rate under in vitro growth conditions, the orlA mutant was virtually avirulent in two distinct murine models of invasive pulmonary aspergillosis. Our results suggest that further study of this pathway will lead to new insights into regulation of fungal cell wall biosynthesis and virulence.

Trehalose accumulation from corn starch by Saccharomycopsis fibuligera A11 during 2-l fermentation and trehalose purification

In this study, corn starch was used as the substrate for cell growth and trehalose accumulation by Saccharomycopsis fibuligera A11. Effect of different aeration rates, agitation speeds, and concentrations of corn starch on direct conversion of corn starch to trehalose by S. fibuligera A11 were examined using a Biostat B2 2-l fermentor. We found that the optimal conditions for direct conversion of corn starch to trehalose by this yeast strain were that agitation speed was 200 rpm, aeration rate was 4.0 l/min, concentration of corn starch was 2.0% (w/v), initial pH was 5.5, fermentation temperature was 30 degrees C. Under these conditions, over 22.9 g of trehalose per 100 g of cell dry weight was accumulated in the yeast cells, cell mass was 15.2 g/l of the fermentation medium, 0.12% (w/v) of reducing sugar, and 0.21% (w/v) of total sugar were left in the fermented medium within 48 h of the fermentation. It was found that trehalose in the yeast cells could be efficiently extracted by the hot distilled water (80 degrees C). After isolation and purification, the crystal trehalose was obtained from the extract of the cells.

Studies on substrate specificity and activity regulating factors of trehalose-6-phosphate synthase of Saccharomyces cerevisiae

Purified trehalose-6-phosphate synthase (TPS) of Saccharomyces cerevisiae was effective over a wide range of substrates, although differing with regard to their relative activity. Polyanions heparin and chondroitin sulfate were seen to stimulate TPS activity, particularly when a pyrimidine glucose nucleotide like UDPG was used, rather than a purine glucose nucleotide like GDPG. A high V(max) and a low K(m) value of UDPG show its greater affinity with TPS than GDPG or TDPG. Among the glucosyl acceptors TPS showed maximum activity with G-6-P which was followed by M-6-P and F-6-P. Effect of heparin was also extended to the purification of TPS activity, as it helped to retain both stability and activity of the final purified enzyme. Metal co-factors, specifically MnCl(2) and ZnCl(2) acted as stimulators, while enzyme inhibitors had very little effect on TPS activity. Metal chelators like CDTA, EGTA stimulated enzyme activity by chelation of metal inhibitors. Temperature and pH optima of the purified enzyme were determined to be 40 degrees C and pH 8.5 respectively. Enzyme activity was stable at 0-40 degrees C and at alkaline pH.

A novel trehalose synthesizing pathway in the hyperthermophilic Crenarchaeon Thermoproteus tenax: the unidirectional TreT pathway

In the genome of the hyperthermophilic archaeon Thermoproteus tenax a gene (treS/P) encoding a protein with similarity to annotated trehalose phosphorylase (TreP), trehalose synthase (TreS) and more recently characterized trehalose glycosyltransferring synthase (TreT) was identified. The treS/P gene as well as an upstream located ORF of unknown function (orfY) were cloned, heterologously expressed in E. coli and purified. The enzymatic characterization of the putative TreS/P revealed TreT activity. However, contrary to the previously characterized reversible TreT from Thermococcus litoralis and Pyrococcus horikoshii, the T. tenax enzyme is unidirectional and catalyzes only the formation of trehalose from UDP (ADP)-glucose and glucose. The T. tenax enzyme differs from the reversible TreT of T. litoralis by its preference for UDP-glucose as co-substrate. Phylogenetic and comparative gene context analyses reveal a conserved organization of the unidirectional TreT and OrfY gene cluster that is present in many Archaea and a few Bacteria. In contrast, the reversible TreT pathway seems to be restricted to only a few archaeal (e.g. Thermococcales) and bacterial (Thermotogales) members. Here we present a new pathway exclusively involved in trehalose synthesis--the unidirectional TreT pathway--and discuss its physiological role as well as its phylogenetic distribution.

Mechanistic differences among retaining disaccharide phosphorylases: insights from kinetic analysis of active site mutants of sucrose phosphorylase and alpha,alpha-trehalose phosphorylase

Sucrose phosphorylase utilizes a glycoside hydrolase-like double displacement mechanism to convert its disaccharide substrate and phosphate into alpha-d-glucose 1-phosphate and fructose. Site-directed mutagenesis was employed to characterize the proposed roles of Asp(196) and Glu(237) as catalytic nucleophile and acid-base, respectively, in the reaction of sucrose phosphorylase from Leuconostoc mesenteroides. The side chain of Asp(295) is suggested to facilitate the catalytic steps of glucosylation and deglucosylation of Asp(196) through a strong hydrogen bond (23 kJ/mol) with the 2-hydroxyl of the glucosyl oxocarbenium ion-like species believed to be formed in the transition states flanking the beta-glucosyl enzyme intermediate. An assortment of biochemical techniques used to examine the mechanism of alpha-retaining glucosyl transfer by Schizophyllum commune alpha,alpha-trehalose phosphorylase failed to provide evidence in support of a similar two-step catalytic reaction via a covalent intermediate. Mutagenesis studies suggested a putative active-site structure for this trehalose phosphorylase that is typical of retaining glycosyltransferases of fold family GT-B and markedly different from that of sucrose phosphorylase. While ambiguity remains regarding the chemical mechanism by which the trehalose phosphorylase functions, the two disaccharide phosphorylases have evolved strikingly different reaction coordinates to achieve catalytic efficiency and stereochemical control in their highly analogous substrate transformations.

Aggregation dependent enhancement of trehalose-6-phosphate synthase activity in Saccharomyces cerevisiae

Trehalose-6-phosphate synthase (TPS) is one of the key subunits of the trehalose synthase complex, responsible for synthesis of trehalose in Saccharomyces cerevisiae. Different laboratories have tried to purify TPS, but have been unable to separate it from the complex. During the present study, active TPS has been isolated from the trehalose synthase complex as a free 59 kDa protein. A 15.8 [corrected] fold purification was achieved with over 84% recovery of active TPS. N-terminal sequence confirmed the 59 kDa protein to be TPS. It was revealed to be a highly hydrophobic protein by amino acid analysis data. Activity of TPS was identified to be governed by association-dissociation of protein components. TPS activity of the isolated enzyme was highly unstable due to dissociation of the protein from the complex. Aggregation of active molecules was also seen to enhance as well as stabilize enzyme activity. This aggregation was concentration dependent and activity was seen to be enhanced by increasing the number of active molecules and fell with dilution. The association of the active complex was also found to be governed by ionic interactions.

Trehalose phosphorylase from Pleurotus ostreatus: Characterization and stabilization by covalent modification, and application for the synthesis of α,α-trehalose

Trehalose phosphorylase from the basidiomycete Pleurotus ostreatus (PoTPase) was isolated from fungal fruit bodies through approximately 500-fold purification with a yield of 44%. Combined analyses by SDS-PAGE and gelfiltration show that PoTPase is a functional monomer of approximately 55 kDa molecular mass. PoTPase catalyzes the phosphorolysis of alpha,alpha-trehalose, yielding alpha-d-glucose 1-phosphate (alphaGlc 1-P) and alpha-d-glucose as the products. The optimum pH of PoTPase for alpha,alpha-trehalose phosphorolysis and synthesis is 6.8 and 6.2, respectively. Apparent substrate binding affinities (K(m)) were determined at pH 6.8 and 30 degrees C: alpha,alpha-trehalose (79 mM); phosphate (3.5 mM); d-glucose (40 mM); alphaGlc 1-P (4.1mM). A series of structural analogues of d-glucose were tested as glucosyl acceptors for the enzymatic reaction with alphaGlc 1-P, and robust activity with d-mannose (3%), 2-deoxy d-glucose (8%), 2-fluoro d-glucose (15%) and 2-keto-d-glucose (50%) was detected. Arsenate replaces, with 30% relative activity, phosphate in the conversion of alpha,alpha-trehalose, and vanadate strongly inhibits the enzyme activity (K(i) approximately 4 microM). PoTPase has a half-life (t(0.5)) of approximately 1 h at 30 degrees C in the absence of stabilizing compounds such as alpha,alpha-trehalose (300 mM; t(0.5)=11.5 h), glycerol (20%, w/v; t(0.5)=6.5h) or polyethylenglycol (PEG) 4000 (26%, w/v; t(0.5)=70 h). Covalent modification of PoTPase with activated derivatives of PEG 5000 increases the stability by up to 600-fold. Sucrose was converted to alpha,alpha-trehalose in approximately 60% yield using a coupled enzyme system composed of sucrose phosphorylase from Leuconostoc mesenteroides, glucose isomerase from Streptomyces murinus and the appropriately stabilized PoTPase.

Enhanced conversion of soluble starch to trehalose by a mutant of Saccharomycopsis fibuligera sdu

In our previous studies, it was found that Saccharomycopsis fibuligera sdu cells could accumulate 18.0% (gg(-1)) trehalose from soluble starch in SSY medium. However, the yeast strain contained high activities of acid and neutral trehalases, which were reported to mobilize trehalose accumulated by the cells during fermentation. In order to enhance the yield of trehalose, it is necessary to remove the trehalase activities from the cells. By mutagenesis of ethylmethanesulfonate, one mutant that assimilated trehalose very slowly, but grew on other carbon sources as fast as its parent strain, was isolated. In Biostat B2 2-1 fermentation, trehalose accumulation of the mutant was much higher than that of the wild type when grown in YPS medium containing starch. The activities of acid and neutral trehalases of this mutant were much lower than those of the wild type, respectively. We think the reduction of acid and neutral trehalase activities is considered to be responsible for the increased yield of trehalose accumulated by the mutant.

Neurospora clock-controlled gene 9 (ccg-9) encodes trehalose synthase: circadian regulation of stress responses and development

The circadian clock of Neurospora crassa regulates the rhythmic expression of a number of genes encoding diverse functions which, as an ensemble, are adaptive to life in a rhythmic environment of alternating levels of light and dark, warmth and coolness, and dryness and humidity. Previous differential screens have identified a number of such genes based solely on their cycling expression, including clock-controlled gene 9 (ccg-9). Sequence analysis now shows the predicted CCG-9 polypeptide to be homologous to a novel form of trehalose synthase; as such it would catalyze the synthesis of the disaccharide trehalose, which plays an important role in protecting many cells from environmental stresses. Consistent with this, heat, glucose starvation, and osmotic stress induce ccg-9 transcript accumulation. Surprisingly, however, a parallel role in development is suggested by the finding that inactivation of ccg-9 results in altered conidiophore morphology and abolishes the normal circadian rhythm of asexual macroconidial development. Examination of a clock component, FRQ, in the ccg-9-null strain revealed normal cycling, phosphorylation, and light induction, indicating that loss of the conidiation rhythm is not due to changes in either the circadian oscillator or light input into the clock but pointing instead to a defect in circadian output. These data imply an interplay between a role of trehalose in stress protection and an apparent requirement for trehalose in clock regulation of conidiation under constant environmental conditions. This requirement can be bypassed by a daily light signal which drives a light-entrained rhythm in conidiation in the ccg-9-null strain; this bypass suggests that the trehalose requirement is related to clock control of development and not to the developmental process itself. Circadian control of trehalose synthase suggests a link between clock control of stress responses and that of development.

Purification and characterization of the heterologously expressed trehalose/maltose ABC transporter complex of the hyperthermophilic archaeon Thermococcus litoralis

We report the purification of the maltose/trehalose transporter complex MalFGK of the hyperthermophilic archaeon Thermococcus litoralis. The complex was expressed in Escherichia coli, solubilized in dodecyl maltoside and purified with the aid of a histidine tag on one of the membrane proteins. One hundred grams of cells yielded 3 mg of pure complex. The final product showed ATPase activity at 70 degrees C and was soluble at low detergent concentration. ATPase activity was not due to dissociation of the MalK subunit from the integral membrane proteins MalF and MalG but could not be further stimulated by trehalose/maltose binding protein (TMBP), be it the native protein as isolated from T. litoralis or the soluble engineered protein. The purified native TMBP was identified as a glycoprotein.

Fungal trehalose phosphorylase: kinetic mechanism, pH-dependence of the reaction and some structural properties of the enzyme from Schizophyllum commune

Initial-velocity measurements for the phospholysis and synthesis of alpha,alpha-trehalose catalysed by trehalose phosphorylase from Schizophyllum commune and product and dead-end inhibitor studies show that this enzyme has an ordered Bi Bi kinetic mechanism, in which phosphate binds before alpha,alpha-trehalose, and alpha-D-glucose is released before alpha-D-glucose 1-phosphate. The free-energy profile for the enzymic reaction at physiological reactant concentrations displays its largest barriers for steps involved in reverse glucosyl transfer to D-glucose, and reveals the direction of phospholysis to be favoured thermodynamically. The pH dependence of kinetic parameters for all substrates and the dissociation constant of D-glucal, a competitive dead-end inhibitor against D-glucose (K(i)=0.3 mM at pH 6.6 and 30 degrees C), were determined. Maximum velocities and catalytic efficiencies for the forward and reverse reactions decrease at high and low pH, giving apparent pK values of 7.2--7.8 and 5.5--6.0 for two groups whose correct protonation state is required for catalysis. The pH dependences of k(cat)/K are interpreted in terms of monoanionic phosphate and alpha-D-glucose 1-phosphate being the substrates, and of the pK value seen at high pH corresponding to the phosphate group in solution or bound to the enzyme. The K(i) value for the inhibitor decreases outside the optimum pH range for catalysis, indicating that binding of D-glucal is tighter with incorrectly ionized forms of the complex between the enzyme and alpha-D-glucose 1-phosphate. Each molecule of trehalose phosphorylase contains one Mg(2+) that is non-dissociable in the presence of metal chelators. Measurements of the (26)Mg(2+)/(24)Mg(2+) ratio in the solvent and on the enzyme by using inductively coupled plasma MS show that exchange of metal ion between protein and solution does not occur at measurable rates. Tryptic peptide mass mapping reveals close structural similarity between trehalose phosphorylases from basidiomycete fungi.