Purification and identification of the essential ionizable groups of honeybee, Apis mellifera L., trehalase

Purification and Functional Characterization of a Soluble Trehalase in Lissorhoptrus oryzophilus (Coleoptera: Curculionidae)

Trehalase is the only enzyme known for the irreversible splitting of trehalose and plays a major role in insect growth and development. In this report, we describe a basic study of the trehalase gene fragment encoding a soluble trehalase from Lissorhoptrus oryzophilus (LoTRE1). Sequence alignment and phylogenetic analysis suggested that LoTRE1 was similar to some known insect trehalases and belongs to the Coleoptera trehalase group. Additionally, LoTRE1 was expressed mainly in the fat body. Purified protein was obtained using heterologous expression of LoTRE1 in Escherichia coli, and the recombinant protein exhibited the ability to decompose trehalose. Enzyme-substrate docking indicated the potential involvement of other residues in the catalytic activity, in addition to Asp 333. Moreover, feeding of adults on LoTRE1 dsRNA silenced the transcription of LoTRE1 and thereby reduced the activity of trehalase and increased the trehalose content; it also led to a 12% death rate. This study reveals essential molecular features of trehalase and offers insights into the structural aspects of this enzyme, which might be related to its function. Taken together, the findings demonstrate that LoTRE1 is indispensable for adults of this pest and provide a new target for the control of L. oryzophilus.

Purification and Characterization of Trehalase From Acyrthosiphon pisum, a Target for Pest Control

Insect trehalases are glycoside hydrolases essential for trehalose metabolism and stress resistance. We here report the extraction and purification of Acyrthosiphon pisum soluble trehalase (ApTreh-1), its biochemical and structural characterization, as well as the determination of its kinetic properties. The protein has been purified by ammonium sulphate precipitation, first followed by an anion-exchange and then by an affinity chromatography. The SDS-PAGE shows a main band at 70 kDa containing two isoforms of ApTreh-1 (X1 and X2), identified by mass spectrometry and slightly contrasting in the C-terminal region. A phylogenetic tree, a multiple sequence alignment, as well as a modelled 3D-structure were constructed and they all reveal the ApTreh-1 similarity to other insect trehalases, i.e. the two signature motifs ¹⁷⁹PGGRFRELYYWDTY¹⁹² and ⁴⁷⁹QWDFPNAWPP⁴⁸⁹, a glycine-rich region ⁵⁴⁹GGGGEY⁵⁵⁴, and the catalytic residues Asp336 and Glu538. The optimum enzyme activity occurs at 45 °C and pH 5.0, with K_m and V_max values of ~ 71 mM and ~ 126 µmol/min/mg, respectively. The present structural and functional characterization of soluble A. pisum trehalase enters the development of new strategies to control the aphids pest without significant risk for non-target organisms and human health.

Conformational changes on ligand binding in wild-type and mutants from Spodoptera frugiperda midgut trehalase

Trehalase specifically hydrolyses trehalose into two glucose units and is most important in insects and fungi. Previous evidence suggested that Spodoptera frugiperda midgut trehalase (wild type, WT) has substantial conformational changes on binding different substances. Our goal is to understand this mobility. For this, two deletion mutants were produced, lacking regions supposed to be the cause of mobility [(102 residues from the N-terminus (NT) and this portion plus 31 residues from the C-terminus (NCT)]. Circular dichroism spectra before and after denaturation of the enzymes support the assertion that they are appropriately folded. The overall results show that the removal of 102 or 133 amino acids does not greatly change the interaction with the substrate and competitive inhibitors, but leads to a considerable decrease in kcat/Km values from WT 74,500 M^-1 s^-1 to NT 647 M^-1 s^-1 and NCT 1,044 M^-1 s^-1. Diethyl pyrocarbonate His modification only occurs in wild and truncated trehalases in the presence of some ligands. Looking for changes in folding WT, NT, and NCT were incubated with different compounds in the presence of Sypro Orange, that binds to hydrophobic regions increasing its fluorescence. The dye fluorescence is affected by 2 compounds when WT is present, and at least by 5 compounds when NT or NCT are present, suggesting that conformational changes caused by ligand binding occur only in the vicinity of the active site. These data provide physical evidence in favor of a change in folding around the active site caused by ligand binding, in agreement to prior chemical modification and other kinetic data and challenging the hypothesis that N- and C-terminal are the mobile regions.

cDNA cloning and characterization of two trehalases from Spodoptera litura (Lepidoptera; Noctuidade)

The oriental leafworm moth, Spodoptera litura, is a major agricultural pest in southeast Asia and nearby Pacific regions. Two distinct trehalases have been identified in insects: soluble trehalase (Treh1) and membrane-bound trehalase (Treh2), although there is currently no information on these genes in S. litura. To characterize the distribution and function of treh, cDNAs of Treh proteins were cloned from S. litura. SpoliTreh1 cDNA has an open reading frame of 1758 nucleotides, which encodes a protein of 585 amino acids, with a predicted mass of approximately 67.07 kDa and an isoelectric point of 4.86. SpoliTreh2 cDNA has an open reading frame of 2325 nucleotides, encoding a protein of 645 amino acids, a mass of approximately 73.62 kDa, and an isoelectric point of 5.90. Northern blotting analysis revealed that SpoliTreh1 transcripts are in the midgut, fat body, tracheae, and epidermis, but not in the brain and Malpighian tubules of S. litura larvae, whereas SpoliTreh2 transcripts were found in all 6 tissues. SpoliTreh1 transcripts were highly expressed in the fat body of the pre-pupal stage, and SpoliTreh2 transcripts were highly expressed in the fat body of 3-day-old larvae of the 6th instar and during the 1st 6 days of the pupal stage, except the 2nd day. Both SpoliTreh1 and SpoliTreh2 were highly expressed in third-instar larvae.

The catalytic and other residues essential for the activity of the midgut trehalase from Spodoptera frugiperda

Trehalase (EC 3.2.1.28) hydrolyzes only α, α'- trehalose and is present in a variety of organisms, but is most important in insects and fungi. Crystallographic data showed that bacterial trehalase has D312 and E496 as the catalytical residues and three Arg residues in the active site. Those residues have homologous in all family 37 trehalases including Spodoptera frugiperda trehalase (D322, E520, R169, R227, R287). To test the role of these residues, mutants of trehalase were produced. All mutants were at least four orders of magnitude less active than wild type trehalase and no structural difference between these mutants and wild type enzyme were discernible by circular dichroism. D322A and E520 pH-activity profile lacked the alkaline arm and the acid arm, respectively, suggesting that D322 is the acid and E520 the basic catalyst. Azide increases E520A activity three times, confirming its action as the basic catalyst. Taking into account the decrease in activity after substitution for alanine residue, the three arginine residues are as important as the catalytical ones to trehalase activity. This clarifies the previous misidentification of an Arg residue as the acid catalyst. As far as we know, this is the first report on the functional identification residues important for trehalase activity.

Sequencing of Spodoptera frugiperda midgut trehalases and demonstration of secretion of soluble trehalase by midgut columnar cells

Both soluble (SfTre1) and membrane-bound (SfTre2) trehalases occur along the midgut of Spodoptera frugiperda larvae. Released SfTre2 was purified as a 67 kDa protein. Its K(m) (1.6 mM) and thermal stability (half life 10 min at 62 degrees C) are different from the previously isolated soluble trehalase (K(m)= 0.47 mM; 100% stable at 62 degrees C). Two cDNAs coding for S. frugiperda trehalases have been cloned using primers based on consensus sequences of trehalases and having as templates a cDNA library prepared from total polyA-containing RNA extracted from midguts. One cDNA codes for a trehalase that has a predicted transmembrane sequence and was defined as SfTre2. The other, after being cloned and expressed, results in a recombinant trehalase with a K(m) value and thermal stability like those of native soluble trehalase. This enzyme was defined as SfTre1 and, after it was used to generate antibodies, it was immunolocalized at the secretory vesicles and at the glycocalyx of columnar cells. Escherichia coli trehalase 3D structure and sequence alignment with SfTre1 support a proposal regarding the residue modulating the pKa value of the proton donor.

Trehalose and trehalase in root nodules of Medicago truncatula and Phaseolus vulgaris in response to salt stress

Trehalose (alpha-D-glucopyranosyl-1,1-alpha-D-glucopyranoside), a non-reducing disaccharide, has been found in a wide variety of organisms playing an important role as an abiotic stress protectant. Plants may come into contact with trehalose from exogenous sources, such as in plant-rhizobia symbiosis in which the rhizobia have the capacity to produce trehalose. The aim of this work is to analyse how trehalose and trehalase respond to salt stress in root nodules of legumes. For this purpose, tissue expression of Medicago truncatula trehalase gene (MTTRE1) and the expression of MTTRE1 under salt stress were analysed by real-time quantitative reverse transcription-PCR method. Trehalase activity was determined and trehalose was also measured by gas chromatography. In addition, trehalase protein occurrence in different organs and at different developmental stages in Phaseolus vulgaris plants has been studied. MTTRE1 expression is induced in nodules compared with leaves and roots, indicating a transcriptional regulation of trehalase in the presence of the microsymbiont. Under salt stress conditions, trehalase activity is downregulated at the transcriptional level, allowing trehalose accumulation. The results found in this study led us to conclude that trehalase activity is induced in root nodules of legumes by the microsymbiont and that under salt stress conditions; trehalase activity is downregulated at the transcriptional level in M. truncatula nodules. This allows trehalose accumulation and supports the possible role of this disaccharide as a stabilizer against salt stress conditions.

Rates of spontaneous cleavage of glucose, fructose, sucrose, and trehalose in water, and the catalytic proficiencies of invertase and trehalas

The half-lives for spontaneous hydrolysis of trehalose and sucrose at 25 °C are 6.6 × 10⁶ years and 440 years. The half-lives for decomposition of the hydrolysis products glucose and fructose are 96 years and 70 days, respectively. Whereas sucrose and trehalose differ by a factor of 15000 in their rates of uncatalyzed hydrolysis, the reactions catalyzed by invertase (EC 3.2.1.26) and trehalase (EC 3.2.1.28) proceed at similar rates. Accordingly, the attainments of invertase as a catalyst are modest, but the rate enhancement and catalytic proficiency produced by trehalase approach the high levels achieved by polysaccharide hydrolases.

Physiological implications of trehalase from Phaseolus vulgaris root nodules: partial purification and characterization

The purification and characterization of trehalase from common bean nodules as well as the role of this enzyme on growth, nodulation nitrogen fixation by examining the effects of the trehalase inhibitor validamycin A, was studied. Validamycin A did not affect plant and nodule mass, neither root trehalase and nitrogenase activity; however this treatment applied at the time of sowing increased nodule number about 16% and decreased nodule trehalase activity (16-fold) and the size of nodules. These results suggest that nodule trehalase activity of Phaseolus vulgaris could be involved in nodule formation and development. In addition, acid trehalase (EC 3.2.1.28) was purified from root nodules by fractionating ammonium sulfate, column chromatography on DEAE-sepharose and sephacryl S-300, and finally on native polyacrylamide gel electrophoresis. The purified homogeneous preparation of native acid trehalase exhibited a molecular mass of 42 and 45 kDa on SDS-PAGE. The enzyme has the optimum pH 3.9, Km of 0.109 mM, Vmax of 3630 nkat mg-1 protein and is relatively heat stable. Besides trehalose, it shows maximal activity with sucrose and maltose and, to a lesser degree melibiose, cellobiose and raffinose, and it does not hydrolyze on lactose and turanose. Acid trehalase was activated by Na+, Mn2+, Mg2+, Li+, Co2+, K+ and inhibited by Fe3+, Hg+ and EDTA.

The role of carboxyl, guanidine and imidazole groups in catalysis by a midgut trehalase purified from an insect larvae

A trehalase (EC 3.2.1.28) of 67 kDa was purified to homogeneity from the midgut of Spodoptera frugiperda (Lepidoptera) larvae. The enzyme is inhibited by toxic beta-glucosides produced by plants (amygdalin, prunasin, salicin and phlorezin) and by their aglycones (mandelonitrile, phloretin). From kcat and Km values determined in different pHs, the pKa values of catalytic essential groups were calculated (pKa = 4.5 and pKa = 8.0). These pKa values agree with the ones determined from enzyme chemical in activation with carbodiimide and phenyl glyoxal, respectively, indicating that the enzyme has a carboxyl group that act as a nucleophile and a guanidine group that is the proton donor during the catalytic cycle. The enzyme has two putative subsites for glucose binding. Based on the protection afforded by ligands against chemical modification, the roles of the subsites were inferred. Thus, the one that binds the competitive inhibitors, methyl alpha-glucoside (MalphaGlu) and mandelonitrile, contains the catalytic carboxyl, whereas the other having the catalytic Arg residue binds the competitive inhibitor Tris. Diethyl pyrocarbonate is ineffective except in the presence of MalphaGlu, when it decreases trehalase activity and changes the pKa value of the catalytic Arg residue. This suggests that the pKa value of the Arg residue is modulated by a His residue located near the active site. This also indicates that the enzyme molecule changes its conformation when the subsite containing the carboxyl group is occupied. The increase in trehalase inactivation by phenyl glyoxal in the presence of MalphaGlu agrees with the last observation.

Purification and characterization of acid trehalase from muscle of Ascaris suum (Nematoda)

Acid trehalase (EC 3.2.1.28) was isolated from muscle of Ascaris suum by fractionating with ammonium sulfate, acetone and column chromatography on DEAE-cellulose and phenyl sepharose CL-4B. The purified homogeneous preparation of native acid trehalase exhibited a molecular mass of 76 kDa and of 38 kDa on SDS-PAGE. The enzyme has the optimum pH 4.9, pI 4.3, Km of 6.6 mM and Vmax=34.5 nM min(-1) x mg(-1). Besides trehalose, it hydrolyses sucrose, isomaltose and maltose and, to a lesser degree melezitose, and it does not act on cellobiose and lactose. Acid trehalase was activated by MgCl2, KNO3, NaCl, CaCl2, CH2ICOOH and p-chloromercuribenzoate and inhibited by EDTA, ZnSO4 and FeCl3.

Alpha-glucosidase mutant catalyzes "alpha-glycosynthase"-type reaction

Replacement of the catalytic nucleophile Asp481 by glycine in Schizosaccharomyces pombe alpha-glucosidase eliminated the hydrolytic activity. The mutant enzyme (D481G) was found to catalyze the formation of an alpha-glucosidic linkage from beta-glucosyl fluoride and 4-nitrophenyl (PNP) alpha-glucoside to produce two kinds of PNP alpha-diglucosides, alpha-isomaltoside and alpha-maltoside. The two products were not hydrolyzed by D481G, giving 41 and 29% yields of PNP alpha-isomaltoside and alpha-maltoside, respectively. PNP monoglycosides, such as alpha-xyloside, alpha-mannoside, or beta-glucoside, acted as the substrate, but PNP alpha-galactoside and maltose could not. No detectable product was observed in the combination of alpha-glucosyl fluoride and PNP alpha-glucoside. This study is the first report on an "alpha-glycosynthase"-type reaction to form an alpha-glycosidic linkage.