Characterization of a trehalose-degrading enzyme from the hyperthermophilic archaeon Sulfolobus acidocaldarius

Exploration of novel trehalases from cold-adapted Variovorax sp. PAMC28711: Functional characterization

The cold-adapted bacterium Variovorax sp. PAMC28711 possesses two distinct glycoside hydrolase (GH) families of trehalase, GH15 and GH37. While numerous studies have explored bacterial trehalase, the presence of two different trehalase genes within a single strain has not been reported until now. Interestingly, despite both GH37 and GH15 trehalases serving the same purpose of degrading trehalose, but do not share the sequence similarity. The substrate specificity assay confirmed that Vtre37 and Vtre15 displayed hydrolytic activity on α, α-trehalose. The key catalytic sites were identified as D280 and E469 in Vtre37 and E389 and E554 in Vtre15 through site-directed mutation and confirmed these two enzymes belong to trehalase. In addition, Vtre37 exhibited a relatively high level of enzyme activity of 1306.33 (±53.091) μmolmg-1, whereas Vtre15 showed enzyme activity of 408.39 (±12.503) μmolmg-1. Moreover, Vtre37 performed admirably showing resistance to ethanol (10 %), with high stable at acidic pH range. Furthermore, both prediction and experimental results indicate that validoxylamine A showed a potent inhibitory activity against Vtre37 trehalase with a Ki value of 16.85 nM. Therefore, we postulate that Vtre37 could be utilized as an ethanol enhancer and designed for screening inhibitors related to the trehalose degradation pathway. Additionally, we believe that characterizing these bacterial trehalase contributes to a better understanding of trehalose metabolism and its biological importance in bacteria.

Elucidation of bacterial trehalose-degrading trehalase and trehalose phosphorylase: physiological significance and its potential applications

Bacteria possess diverse metabolic and genetic processes, resulting in the inability of certain bacteria to degrade trehalose. However, some bacteria do have the capability to degrade trehalose, utilizing it as a carbon source, and for defense against environmental stress. Trehalose, a disaccharide, serves as a carbon source for many bacteria, including some that are vital for pathogens. The degradation of trehalose is carried out by enzymes like trehalase (EC 3.2.1.28) and trehalose phosphorylase (EC 2.4.1.64/2.4.1.231), which are classified under the glycoside hydrolase families GH37, GH15, and GH65. Numerous studies and reports have explored the physiological functions, recombinant expression, enzymatic characteristics, and potential applications of these enzymes. However, further research is still being conducted to understand their roles in bacteria. This review aims to provide a comprehensive summary of the current understanding of trehalose degradation pathways in various bacteria, focusing on three key areas: (i) identifying different trehalose-degrading enzymes in Gram-positive and Gram-negative bacteria, (ii) elucidating the mechanisms employed by trehalose-degrading enzymes belonging to the glycoside hydrolases GH37, GH15, and GH65, and (iii) discussing the potential applications of these enzymes in different sectors. Notably, this review emphasizes the bacterial trehalose-degrading enzymes, specifically trehalases (GH37, GH15, and GH65) and trehalose phosphorylases (GH65), in both Gram-positive and Gram-negative bacteria, an aspect that has not been highlighted before.

Identification and Characterization of a Novel Cold-Adapted GH15 Family Trehalase from the Psychrotolerant Microbacterium phyllosphaerae LW106

Psychrophiles inhabiting various cold environments are regarded as having evolved diverse physiological and molecular strategies, such as the accumulation of trehalose to alleviate cold stress. To investigate the possible contributions of trehalose metabolism-related enzymes to cold-adaption in psychrotrophic bacteria and enrich the resource bank of trehalose hydrolysis enzymes, a novel cold-adapted GH15 GA-like trehalase (MpTre15A) from psychrotolerant Microbacteriumphyllosphaerae LW106 isolated from glacier sediments was cloned and characterized. The recombinant MpTre15A from M. phyllosphaerae LW106 was expressed and purified in Escherichia coli BL21(DE3). The purified MpTre15A functioned as a hexamer and displayed maximal activity at pH 5.0 and 50 °C. Substrate specificity assay proved MpTre15A only showed hydrolytic activity toward α,α-trehalose. Site-directed mutation verified the key catalytic sites of Glu392 and Glu557 in MpTre15A. The kcat and kcat/Km values of MpTre15A at 4 °C (104.50 s−1 and 1.6 s−1 mM−1, respectively) were comparable to those observed for thermophilic GH15 trehalases at 50 °C, revealing its typical cold-adaptability. MpTre15A showed a trehalose conversion rate of 100% and 99.4% after 10 min and 15 min of incubation at 50 °C and 37 °C, respectively. In conclusion, this novel cold-adapted α,α-trehalase MpTre15A showed potential application for developing therapeutic enzymes, enzyme-based biosensors, and enzyme additives in the fermentation industry.

Expression and characterization of a novel trehalase from Microvirga sp. strain MC18

Trehalase catalyzes the hydrolysis of trehalose into two glucose molecules and is present in nearly all tissues in various forms. In this study, a putative bacterial trehalase gene, encoding a glycoside hydrolase family 15 (GH15) protein was identified in Microvirga sp. strain MC18 and heterologously expressed in E. coli. The specific activity of the purified recombinant trehalase MtreH was 24 U/mg, with K_m and V_max values of 23.45 mg/mL and 184.23 μmol/mg/min, respectively. The enzyme exhibited optimal activity at 40 °C and pH 7.0, whereby Ca²⁺ had a considerable positive effects on the catalytic activity and thermostability. The optimized enzymatic reaction conditions for the bioconversion of trehalose using rMtreH were determined as 40 °C, pH 7.0, 10 h and 1% trehalose concentration. The characterization of this bacterial trehalase improves our understanding of the metabolism and biological role of trehalose in prokaryotic organism.

Salt Stress Response of Sulfolobus acidocaldarius Involves Complex Trehalose Metabolism Utilizing a Novel Trehalose-6-Phosphate Synthase (TPS)/Trehalose-6-Phosphate Phosphatase (TPP) Pathway

The crenarchaeon Sulfolobus acidocaldarius has been described to synthesize trehalose via the maltooligosyltrehalose synthase (TreY) and maltooligosyltrehalose trehalohydrolase (TreZ) pathway, and the trehalose glycosyltransferring synthase (TreT) pathway has been predicted. Deletion mutant analysis of strains with single and double deletions of ΔtreY and ΔtreT in S. acidocaldarius revealed that in addition to these two pathways, a third, novel trehalose biosynthesis pathway is operative in vivo: the trehalose-6-phosphate (T6P) synthase/T6P phosphatase (TPS/TPP) pathway. In contrast to known TPS proteins, which belong to the GT20 family, the S. acidocaldarius TPS belongs to the GT4 family, establishing a new function within this group of enzymes. This novel GT4-like TPS was found to be present mainly in the Sulfolobales The ΔtreY ΔtreT Δtps triple mutant of S. acidocaldarius, which lacks the ability to synthesize trehalose, showed no altered phenotype under standard conditions or heat stress but was unable to grow under salt stress. Accordingly, in the wild-type strain, a significant increase of intracellular trehalose formation was observed under salt stress. Quantitative real-time PCR showed a salt stress-mediated induction of all three trehalose-synthesizing pathways. This demonstrates that in Archaea, trehalose plays an essential role for growth under high-salt conditions.IMPORTANCE The metabolism and function of trehalose as a compatible solute in Archaea was not well understood. This combined genetic and enzymatic approach at the interface of microbiology, physiology, and microbial ecology gives important insights into survival under stress, adaptation to extreme environments, and the role of compatible solutes in Archaea Here, we unraveled the complexity of trehalose metabolism, and we present a comprehensive study on trehalose function in stress response in S. acidocaldarius This sheds light on the general microbiology and the fascinating metabolic repertoire of Archaea, involving many novel biocatalysts, such as glycosyltransferases, with great potential in biotechnology.

Diverse and common features of trehalases and their contributions to microbial trehalose metabolism

Trehalose is a stable disaccharide that consists of two glucose units linked primarily by an α,α-(1 → 1)-linkage, and it has been found in a wide variety of organisms. In these organisms, trehalose functions not only as a source of carbon energy but also as a protector against various stress conditions. In addition, this disaccharide is attractive for use in a wide range of applications due to its bioactivities. In trehalose metabolism, direct trehalose-hydrolyzing enzymes are known as trehalases, which have been reported for bacteria, archaea, and eukaryotes, and are classified into glycoside hydrolase 37 (GH37), GH65, and GH15 families according to the Carbohydrate-Active enZyme (CAZy) database. The catalytic domains (CDs) of these enzymes commonly share (α/α)₆-barrel structures and have two amino acid residues, Asp and/or Glu, that function as catalytic residues in an inverting mechanism. In this review, I focus on diverse and common features of trehalases within different GH families and their contributions to microbial trehalose metabolism.

Early Response of Sulfolobus acidocaldarius to Nutrient Limitation

In natural environments microorganisms encounter extreme changes in temperature, pH, osmolarities and nutrient availability. The stress response of many bacterial species has been described in detail, however, knowledge in Archaea is limited. Here, we describe the cellular response triggered by nutrient limitation in the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius. We measured changes in gene transcription and protein abundance upon nutrient depletion up to 4 h after initiation of nutrient depletion. Transcript levels of 1118 of 2223 protein coding genes and abundance of approximately 500 proteins with functions in almost all cellular processes were affected by nutrient depletion. Our study reveals a significant rerouting of the metabolism with respect to degradation of internal as well as extracellular-bound organic carbon and degradation of proteins. Moreover, changes in membrane lipid composition were observed in order to access alternative sources of energy and to maintain pH homeostasis. At transcript level, the cellular response to nutrient depletion in S. acidocaldarius seems to be controlled by the general transcription factors TFB2 and TFEβ. In addition, ribosome biogenesis is reduced, while an increased protein degradation is accompanied with a loss of protein quality control. This study provides first insights into the early cellular response of Sulfolobus to organic carbon and organic nitrogen depletion.

Evolutionary and structure-function analysis elucidates diversification of prokaryotic and eukaryotic trehalases

Trehalase catalyses the breakdown of trehalose into two glucose moieties and is ubiquitous in all organisms. Here, we provide insights into the enigmatic origin and evolution of trehalase in major species. Study of taxonomic distribution, orthology, phylogeny and functional domains indicated that trehalase possibly originates from bacteria and was transmitted to other taxa through horizontal gene transfer. Domain analysis showed that glycosyl hydrolase family 37 is present in most of the sequences and represents dominant activity during evolution, and also, illustrating that cytosolic trehalase is primitive than its transmembrane form. Furthermore, it was observed that trehalase went through domain rearrangement to facilitate its activity in adverse environmental conditions like acidic pH. Gene context analysis depicts that trehalase neighbourhood consists of sugar transport and lipid metabolism genes. This highlights their relatedness in metabolic activity and similarity in gene regulation, respectively. Evolutionary and selection pressure analysis demonstrated that trehalase genes were duplicated and evolved under purifying selection, following horizontal gene transfer. Moreover, site-specific rate of evolution emphasized conservation of functionally important residues. In comparison with acid trehalase, neutral trehalase has an extra N-terminal extension. This study serves as an instigation to understand evolution and functionality of trehalase across diverse species. Communicated by Ramaswamy H. Sarma.

Two trehalose-hydrolyzing enzymes from Crenarchaeon Sulfolobus acidocaldarius exhibit distinct activities and affinities toward trehalose

Two archaeal trehalase-like genes, Saci1250 and Saci1816, belonging to glycoside hydrolase family 15 (GH15) from the acidophilic Crenarchaeon Sulfolobus acidocaldarius were expressed in Escherichia coli. The gene products showed trehalose-hydrolyzing activities, and the names SaTreH1 and SaTreH2 were assigned to Saci1816 and Saci1250 gene products, respectively. These newly identified enzymes functioned within a narrow range of acidic pH values at elevated temperatures, which is similar to the behavior of Euryarchaeota Thermoplasma trehalases. SaTreH1 displayed high K_M and k_cat values, whereas SaTreH2 had lower K_M and k_cat values despite a high degree of identity in their primary structures. A mutation analysis indicated that two glutamic acid residues in SaTreH1, E374 and E574, may be involved in trehalase catalysis because SaTreH1 E374Q and E574Q showed greatly reduced trehalose-hydrolyzing activities. Additional mutations substituting G573 and H575 residues with serine and glutamic acid residues, respectively, to mimic the TVN1315 sequence resulted in a decrease in trehalase activity and thermal stability. Taken together, the results indicated that Crenarchaea trehalases adopt active site structures that are similar to Euryarchaeota enzymes but have distinct molecular features. The identification of these trehalases could extend our understanding of the relationships between the structure and function of GH15 trehalases as well as other family enzymes and will provide insights into archaeal trehalose metabolism.