Active site characterization and molecular cloning of Tenebrio molitor midgut trehalase and comments on their insect homologs

The soluble midgut trehalase from Tenebrio molitor (TmTre1) was purified after several chromatographic steps, resulting in an enzyme with 58 kDa and pH optimum 5.3 (ionizing active groups in the free enzyme: pK(e1) = 3.8 ± 0.2 pK(e2) = 7.4 ± 0.2). The purified enzyme corresponds to the deduced amino acid sequence of a cloned cDNA (TmTre1-cDNA), because a single cDNA coding a soluble trehalase was found in the T. molitor midgut transcriptome. Furthermore, the mass of the protein predicted to be coded by TmTre1-cDNA agrees with that of the purified enzyme. TmTre1 has the essential catalytic groups Asp 315 and Glu 513 and the essential Arg residues R164, R217, R282. Carbodiimide inactivation of the purified enzyme at different pH values reveals an essential carboxyl group with pKa = 3.5 ± 0.3. Phenylglyoxal modified a single Arg residue with pKa = 7.5 ± 0.2, as observed in the soluble trehalase from Spodoptera frugiperda (SfTre1). Diethylpyrocarbonate modified a His residue that resulted in a less active enzyme with pK(e1) changed to 4.8 ± 0.2. In TmTre1 the modified His residue (putatively His 336) is more exposed than the His modified in SfTre1 (putatively His 210) and that affects the ionization of an Arg residue. The architecture of the active site of TmTre1 and SfTre1 is different, as shown by multiple inhibition analysis, the meaning of which demands further research. Trehalase sequences obtained from midgut transcriptomes (pyrosequencing and Illumina data) from 8 insects pertaining to 5 different orders were used in a cladogram, together with other representative sequences. The data suggest that the trehalase gene went duplication and divergence prior to the separation of the paraneopteran and holometabolan orders and that the soluble trehalase derived from the membrane-bound one by losing the C-terminal transmembrane loop.

Expression, purification, and characterization of recombinant Metarhizium anisopliae acid trehalase in Pichia pastoris

The mature peptide of Metarhizium anisopliae acid trehalase (ATM1) (EC3.2.1.28) was successfully expressed in Pichia pastoris at high levels under the control of AOX1 promoter. The recombinant ATM1 (reATM1) was secreted into culture medium. After 48-h 0.5% methanol induction, the activity of reATM1 in the culture supernatant reached the peak, 5.35 U/mg. Enzyme with a histidine sequence appended to the C terminus was still active and was purified using metal-chelate affinity chromatography. The yield of purified reATM1 was 2.5 mg from 1L supernatant. The purified reATM1 exhibited a molecular mass of approximately 170 kDa on SDS-PAGE. The optimum temperature and pH of reATM1 were 30 degrees C and 6.0, respectively, and the K(m) and V(max) values for reATM1 were 2.6 mM and 0.305 mmol/min/mg, respectively. Studies showed that the enzymatic properties of reATM1 were similar to those of the native ATM1.

Solubilization and characterization of a cell wall-bound trehalase from ascospores of the fission yeast Schizosaccharomyces pombe

The genome of the fission yeast Schizosaccharomyces pombe lacks sequence homologs to ath1 genes coding for acid trehalases in other yeasts or filamentous fungi. However, acid trehalase activity is present at the spore stage in the life cycle of the fission yeast. The enzyme responsible for this activity behaves as a surface enzyme covalently linked to the spore cell walls in both wild-type and ntp1 mutant strains devoid of neutral trehalase. Lytic treatment of particulated cell wall fractions allowed the solubilization of the enzyme into an active form. We have characterized this soluble enzyme and found that its kinetic parameters, optimum pH and temperature, thermal denaturation and salt responses are closely similar to other conventional acid trehalases. Hence, this rather unusual enzyme can be recognized as acid trehalase by its biochemical properties although it does not share genetic homology with other known acid trehalases. The potential role of such acid trehalase in the mobilization of trehalose is discussed.

Isoforms of trehalase and invertase of Fusarium oxysporum

Enzymatic assays and native PAGE were used to study trehalase and invertase activities, depending on culture age and different sugar conditions, in cell-free extracts, culture filtrates and ribosomal wash of Fusarium oxysporum. The activity of invertase preceded that of trehalase; in the exponential phase of growth, mainly invertase activity was produced, whereas trehalase activity was high in the stationary phase. In this last phase of growth, the activity of intracellular trehalase was repressed by monosaccharides, whereas disaccharides, especially lactose and starch, enhanced the activity of intracellular and extracellular trehalase. However, invertase activity was not repressed under these conditions and had the maximal activity in the presence of saccharose. Intracellular trehalase appeared in a single, high-molecular weight (120 kDa) form, whereas the extracellular enzyme appeared in a single, low-molecular weight (60 kDa) form. The activity pattern of invertase isoforms indicated the occurrence of three forms of intracellular enzyme with the main activity band at 120 kDa and two isoforms of extracellular enzyme. In the ribosomal wash, high-molecular weight isoforms of both trehalase and invertase were identified. A possible role of trehalase and invertase in carbohydrate metabolism of fungal pathogens is also discussed.

A highly thermostable trehalase from the thermophilic bacterium Rhodothermus marinus

Trehalases play a central role in the metabolism of trehalose and can be found in a wide variety of organisms. A periplasmic trehalase (alpha,alpha-trehalose glucohydrolase, EC 3.2.1.28) from the thermophilic bacterium Rhodothermus marinus was purified and the respective encoding gene was identified, cloned and overexpressed in Escherichia coli. The recombinant trehalase is a monomeric protein with a molecular mass of 59 kDa. Maximum activity was observed at 88 degrees C and pH 6.5. The recombinant trehalase exhibited a K(m) of 0.16 mM and a V(max) of 81 micromol of trehalose (min)(-1) (mg of protein)(-1) at the optimal temperature for growth of R. marinus (65 degrees C) and pH 6.5. The enzyme was highly specific for trehalose and was inhibited by glucose with a K(i) of 7 mM. This is the most thermostable trehalase ever characterized. Moreover, this is the first report on the identification and characterization of a trehalase from a thermophilic bacterium.

Characterisation of an acid trehalase produced by the thermotolerant fungus Rhizopus microsporus var. rhizopodiformis: biochemical properties and immunochemical localisation

An acid trehalase from Rhizopus microsporus var. rhizopodiformis was purified to apparent homogeneity. The molecular weight by SDS-PAGE (60 kDa) or Sephacryl S-200 filtration (105 kDa) suggested a homodimer. The carbohydrate content was 72%. Endoglycosidase H digestion resulted in one sharp band of 51.5 kDa in SDS-PAGE. pH and temperature optima were 4.5 and 45 degrees C, respectively. The isoelectric point was 6.69 and activation energy was 1.14 kcal mol(-1). The enzyme was stable for 1 h at 50 degrees C and decayed at 60 degrees C (t50 of 1.3 min.). Apparent KM for trealose was 0.2mM. Immunolocalisation studies showed the enzyme tightly packed at the surface of the cells.

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.

Nucleotide sequence variation does not relate to differences in kinetic properties of neutral trehalase from the insect pathogenic fungus Metarhizium anisopliae

Genetic variability in a putative virulence factor, the neutral trehalase ( Ntl) gene, was examined in strains of the insect pathogenic fungi Metarhizium anisopliae and Metarhizium flavoviride by restriction fragment length polymorphism (RFLP). The Ntl gene was sequenced from four of these strains that showed dissimilar RFLP patterns. Enzyme kinetic experiments were also performed on the partially purified neutral trehalase in order to assess whether nucleotide changes in these strains related to differences in enzyme catalytic function (i.e., Km, Vmax, and Kcat). Finally, the Metarhizium strains were assessed in bioassays against waxworm larvae in order to relate nucleotide variation with Ntl enzyme kinetics and insect virulence. The greatest RFLP variation was observed with Rsa1. M. flavoviride was found to be most dissimilar in RFLP patterns when compared with the M. anisopliae strains. RFLP patterns for Ntl were diagnostic markers for previously studied genetic groups of M. anisopliae. Comparisons of Ntl sequences showed that the introns were found to be more variable (6.2%) than the exons (3.1%). Comparisons of the translated nucleotide codons showed high levels (91%) of synonymous sequence variation between strains. Another fraction of the remaining mutations was neutral, resulting in amino acid substitutions with similar functions. The neutral trehalase was partially purified by preparative isoelectric focus, revealing a single band of enzyme activity as assessed by analytical isoelectric focusing (pI ca. 5). Kinetic properties of the neutral trehalases revealed no differences between the M. anisopliae strains, while the M. flavovoride had a lower Kcat/Km. However, there was lower virulence in one strain that showed Ntl enzyme kinetic properties that were similar to the other strains, suggesting that factors other than neutral trehalase may be responsible for delimiting virulence in this insect pathogenic fungi. Although there is nucleotide variation in genes involved in pathogenicity, this variation is mostly neutral in nature, and there is strong stabilizing selection to maintain enzyme function.

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.

Midgut adaptation and digestive enzyme distribution in a phloem feeding insect, the pea aphid Acyrthosiphon pisum

Transmission electron micrographs of the pea aphid midgut revealed that its anterior region has cells with an apical complex network of lamellae (apical lamellae) instead of the usual regularly-arranged microvilli. These apical lamellae are linked to one another by trabeculae. Modified perimicrovillar membranes (MPM) are associated with the lamellae and project into the lumen. Trabeculae and MPM become less conspicuous along the midgut. The most active A. pisum digestive enzymes are membrane-bound. An aminopeptidase (APN) is described elsewhere. An alpha-glucosidase (alpha-Glu) has a molecular mass of 72 kDa, pH optimum 6.0 and catalyzes in vitro transglycosylations in the presence of an excess of the substrate sucrose. There is a major cysteine proteinase activity (CP) on protein substrates that has a molecular mass of 40 kDa, pH optimum 5.5, is inhibited by E-64 and chymostatin and is activated by EDTA+cysteine. The enzyme is more active against carbobenzoxy-Phe-Arg-4-methylcoumarin-7-amide (ZFRMCA) than against ZRRMCA. These features identify the purified CP as a cathepsin-L-like cysteine proteinase. Most CP is found in the anterior midgut, whereas alpha-Glu and APN predominate in the posterior midgut. With the aid of antibodies, alpha-Glu and CP were immunolocalized in cell vesicles and MPM, whereas APN was localized in vesicles, apical lamellae and MPM. The data suggest that the anterior midgut is structurally reinforced to resist osmotic pressures and that the transglycosylating alpha-Glu, together with CP and APN are bound to MPM, thus being both distributed over a large surface and prevented from excretion with honeydew. alpha-Glu frees glucose from sucrose without increasing the osmolarity, and CP and APN may process toxins or other proteins occasionally present in phloem.

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

Trehalase (EC 3.2.1.28) of the bound type was purified as an electrophoretically homogeneous protein from adult honeybees by fractionation with ammonium sulfate, hydrophobic chromatography, and DEAE-Sepharose CL-6B, CM-Sepharose CL-6B, butyl-Toyopearl 650M, and p-aminophenyl beta-glucoside Sepharose 4B column chromatographies. The enzyme preparation was confirmed to be a monomeric protein containing 3.1% carbohydrate. The molecular weight was estimated to be approximately 69,000, and the optimum pH was 6.7. The Michaelis constant (Km) was 0.66 mM, and the molecular activity (k0) was 86.2 s(-1). The enzyme was an "inverting" type which produced beta-glucose from alpha, alpha-trehalose. Dependence of the V and Km values on pH gave values for the ionization constants, pKe1 and pKe2, of essential ionizable groups 1 and 2 of the free enzyme of 5.3 and 8.5, respectively. When the dielectric constant of the reaction mixture was decreased, pKe1, and pKe2 were shifted to higher values of + 0.2 and + 0.5 pH unit, respectively. The ionization heat (deltaH) of ionizable group 1 was estimated to be + 1.8 kcal/mol, and the deltaH value of group 2 was + 1.5 kcal/mol. These findings strongly support the notion that the essential ionizable groups of honeybee trehalase are two kinds of carboxyl groups, one being a dissociated type (-COO(-), ionizable group 1) and the other a protonated type (-COOH, ionizable group 2), although the pKe2 value is high.

Multiple effects of protein phosphatase 2A on nutrient-induced signalling in the yeast Saccharomyces cerevisiae

The trehalose-degrading enzyme trehalase is activated upon addition of glucose to derepressed cells or in response to nitrogen source addition to nitrogen-starved glucose-repressed yeast (Saccharomyces cerevisiae) cells. Trehalase activation is mediated by phosphorylation. Inactivation involves dephosphorylation, as trehalase protein levels do not change upon multiple activation/inactivation cycles. Purified trehalase can be inactivated by incubation with protein phosphatase 2A (PP2A) in vitro. To test whether PP2A was involved in trehalase inactivation in vivo, we overexpressed the yeast PP2A isoform Pph22. Unexpectedly, the moderate (approximately threefold) overexpression of Pph22 that we obtained increased basal trehalase activity and rendered this activity unresponsive to the addition of glucose or a nitrogen source. Concomitant with higher basal trehalase activity, cells overexpressing Pph22 did not store trehalose efficiently and were heat sensitive. After the addition of glucose or of a nitrogen source to starved cells, Pph22-overexpressing cells showed a delayed exit from stationary phase, a delayed induction of ribosomal gene expression and constitutive repression of stress-regulated element-controlled genes. Deletion of the SCH9 gene encoding a protein kinase involved in nutrient-induced signal transduction restored glucose-induced trehalase activation in Pph22-overexpressing cells. Taken together, our results indicate that yeast PP2A overexpression leads to the activation of nutrient-induced signal transduction pathways in the absence of nutrients.

A comparison of thermal characteristics and kinetic parameters of trehalases from a thermophilic and a mesophilic fungus

Trehalases from a thermophilic fungus Thermomyces lanuginosus (M(r) 145 kDa) and a mesophilic fungus Neurospora crassa (M(r) 437 kDa) were purified to compare their thermal characteristics and kinetic constants. Both trehalases were maximally active at 50 degrees C, had an acidic pH optimum and were glycoproteins (20% and 43%, w/w, carbohydrate content for T. lanuginosus and N. crassa, respectively). At their temperature optimum, their K(m) was similar (0.57 and 0.52 mM trehalose, for T. lanuginosus and N. crassa, respectively) but the V(max) of N. crassa enzyme was nine times higher than of T. lanuginosus enzyme. The catalytic efficiency, k(cat)/K(m), for N. crassa trehalase was one order of magnitude higher (6.2 x 10(6) M(-1) s(-1)) than of T. lanuginosus trehalase (4 x 10(5) M(-1) s(-1)). At their T(opt) (50 degrees C), trehalase from both sources exhibited similar thermostability (t(1/2)6 h). The energy of activation, E(a), for T. lanuginosus trehalase was 15.12 kcal mol(-1) and for N. crassa trehalase it was 9.62 kcal mol(-1). The activation energy for thermal inactivation for the N. crassa enzyme (92 kcal mol(-1)) was two-fold higher than for the T. lanuginosus enzyme (46 kcal mol(-1)). The present study shows that the trehalase of N. crassa is not only more stable but also a better catalyst than the T. lanuginosus enzyme.

Purification of the trehalase GMTRE1 from soybean nodules and cloning of its cDNA. GMTRE1 is expressed at a low level in multiple tissues

Trehalose (alpha-D-glucopyranosyl-1,1-alpha-D-glucopyranoside), a disaccharide widespread among microbes and lower invertebrates, is generally believed to be nonexistent in higher plants. However, the recent discovery of Arabidopsis genes whose products are involved in trehalose synthesis has renewed interest in the possibility of a function of trehalose in higher plants. We previously showed that trehalase, the enzyme that degrades trehalose, is present in nodules of soybean (Glycine max [L.] Merr.), and we characterized the enzyme as an apoplastic glycoprotein. Here we describe the purification of this trehalase to homogeneity and the cloning of a full-length cDNA encoding this enzyme, named GMTRE1 (G. max trehalase 1). The amino acid sequence derived from the open reading frame of GMTRE1 shows strong homology to known trehalases from bacteria, fungi, and animals. GMTRE1 is a single-copy gene and is expressed at a low but constant level in many tissues.

Comparative studies of suidatrestin, a specific inhibitor of trehalases

Suidatrestin, isolated from a Streptomyces strain, was characterized as a new trehalase inhibitor. Its inhibitory potential was 7 to 50-fold higher than that of validamycin when tested against insect, fungal and mammalian trehalases. The kinetic properties of suidatrestin were studied in vitro with trehalases from flight muscle mitochondria of the fly, Protophormia terraenovae, from larval midgut of the moth, Spodoptera littoralis, and from porcine kidney, as well as with maltase from yeast. Suidatrestin was inactive on maltase but inhibited all trehalases with IC50 values of 0.08-0.1 microM; Ki values ranged from 0.02 to 0.05 microM. The very low Ki/K(m) ratios (3.9 x 10(-6) -4.9 x 10(-6)) indicated excellent in vitro inhibitory action of suidatrestin. When injected into larvae of S. littoralis, suidatrestin required high and repetitive doses which lead to reversible inhibition of larval growth only. Consecutive omission of the inhibitor even stimulated weight increase above that of controls. Significant mortality was achieved at a rather high dose only. Injection of a growth-inhibiting dose of suidatrestin did not change hemolymph osmolality as a measure of sugar concentration. The discrepancy between in vitro and in vivo potency of suidatrestin may be understood once its chemical structure is fully known.

Regulation of acid trehalase activity by association-dissociation in Saccharomyces cerevisiae

Acid trehalase (AT) has always been reported to be copurified with invertase (I) and a 40 kDa additional protein. Glucose grown stationary phase cells of Saccharomyces cerevisiae contained least I activity. So, it was attempted to purify AT from these cells (I:AT = 10.83). Studies on specific activity, percent recovery and I:AT ratio of different pools, collected during purification of AT, indicated that samples containing ratio I:AT < 2.2 were unstable. Purification methodology favouring association (DEAE-Sephadex chromatography) resulted in gaining total activity while methodology favouring dissociation (HPGPLC) resulted in tremendous loss in recovery. Active pool (Pool 1X) appeared to be electrophoretically homogeneous but dissociated into 175, 90, 68, 61, 57 (minor bands) and 37-41 (major band) molar mass (kDa) bands on SDS-PAGE. Inactive pools (Pools 1Y, 3X, 3Y) did not contain the 37-41 kDa major band. So, association of both I and a 37-41 kDa protein with AT appeared to be essential. Two bands of isoelectric pH (pI) 4.6 and 4.7 were present in pool 1X enzyme preparation. All SDS-PAGE-resolved bands of pool 1X, in an average, contained high aspartate/asparagine and low cysteine residues. AT activity appeared to be highly sensitive to the change in pH and also to agents affecting ionisation of protein, e.g., betaine, NaCl, acetate, etc. Association of AT components in presence of NaCl was demonstrated spectrophotometrically. Specific activity of AT decreased with dilution. Substrate mediated allosterism for this enzyme preparation suggested that AT existed as an equilibrium mixture of protomer-oligomer. It was suggested that reversible association-dissociation was a mechanism for the regulation of AT activity.

The effect of metacestodes of Hymenolepis diminuta on the bean-shaped accessory glands in male Tenebrio molitor

Metacestodes of Hymenolepis diminuta affect several aspects of female reproductive physiology in Tenebrio molitor and such effects are mediated via the endocrine system. The effects on male reproduction are less well known and were studied with respect to the Bean-Shaped Accessory Glands (BAGs). The size and wet and dry weight of BAGs from infected and uninfected beetles were compared and rose to a plateau from 0-6 days post-emergence in uninfected beetles but in infected individuals continued to increase in both size and weight. These effects were density independent. Glands from both infected and uninfected beetles were assayed for trehalase activity measured by its ability to convert the sugar trehalose to glucose. The activity of this enzyme, per mg wet weight, was not affected by the parasite. However, total activity per gland increased in infected males. Total protein content and electrophoretic profiles of BAGs from infected and uninfected individuals showed no change in profile but showed an increase in all protein subunits per gland over a broad molecular weight range.

Molecular cloning, sequencing and expression of cDNA encoding human trehalase

A complete cDNA clone encoding human trehalase, a glycoprotein of brush-border membranes, has been isolated from a human kidney library. The cDNA encodes a protein of 583 amino acids with a calculated molecular weight of 66,595. Human enzyme contains a typical cleavable signal peptide at amino terminus, five potential glycosylation sites, and a hydrophobic region at carboxyl terminus where the protein is anchored to plasma membranes via glycosylphosphatidylinositol. The deduced amino acid sequence of the human enzyme showed similarity to sequences of the enzyme from rabbit, silk worm, Tenebrio molitor, Escherichia coli and yeast. Northern blots revealed that human trehalase mRNA of approx. 2.0 kb was found mainly in the kidney, liver and small intestine. Expression of the recombinant trehalase in E. coli provided a high level of the enzyme activity. The isolation and expression of cDNA for human trehalase should facilitate studies of the structure of the gene, as well as a basis for a better understanding of the catalytic mechanism.

Trehalases from spores and vegetative cells of yeast Saccharomyces cerevisiae

Trehalase (THA) activity from S. cerevisiae spores and vegetative cells could be differentiated in cell-free extracts. THA from the vegetative cells has an optimal activity at neutral pH whereas biphase pH optimum in the spores was observed. The enzyme from the spores exhibited higher thermostability than that from the vegetative cells. The presence of magnesium ions was necessary mainly for THA activity from the vegetative cells. The effect of the other metal ions studied: Hg2+, Ag2+, Cu2+, Fe3+, Ni2+, Cd2+ etc. (Table II), on THA from both sources was almost the same, however, the spores THA was resistant to Pb2+ and especially to Zn2+. Moreover, the influence of inorganic polyphosphates and polyamines was also quite dissimilar. Polyphosphates inhibited THA from the vegetative cells and to a smaller extent from the spores. On the other hand, polyamines stimulated highly THA activity from vegetative yeast cells in contrast to spores one. The effect of these ions modulators would facilitate differentiating of THA activity in the cell-free extracts from both sources. These data could be interpreted as phenotypic reflections of trehalase genes expression in the S. cerevisiae cells.

Trehalase of Dictyostelium discoideum: inhibition by amino-containing analogs of trehalose and affinity purification

The inhibitory effects of three nitrogen containing analogs of trehalose, validamycin A, MDL 25,637 and castanospermine, on Dictyostelium discoideum trehalase were examined. Prior to this study, the effects of glycohydrolase inhibitors on D discoideum trehalase have not been reported. Validamycin A, MDL 25,637 and castanospermine were found to be potent, reversible, competitive inhibitors of D discoideum vegetative trehalase in vitro with IC50 values of 1 x 10(-9) M, 2 x 10(-8) M and 1.25 x 10(-4) M, respectively. Validamycin A and MDL 25,637 also exhibited time-dependent inhibition of D discoideum trehalase, whereby the potencies of these two inhibitors were observed to increase when pre-incubated with the enzyme for up to 60 min. The competitive natures of validamycin A and MDL 25,637 were also altered during pre-incubation with enzyme such that the compounds behaved as mixed inhibitors under these conditions. Taken together, these results suggest that the inhibitory action of validamycin A and MDL 25,637 on trehalase is of a slow-binding nature. A trehalase-specific affinity resin was synthesized by covalently coupling validamycin A to Sepharose 6B. This resin was used to purify D discoideum trehalase to near homogeneity in a two-step procedure. SDS-PAGE of affinity-purified trehalase, and silver staining or in situ staining for trehalase activity, revealed a major protein species of 42 kDa, exhibiting trehalase activity, and two minor protein species of approximately 45 and 49 kDa. Since validamycin A demonstrates strict binding specificity for trehalase, validamycin A-Sepharose has potential and novel applications in rapid, large scale, purification of trehalases from a variety of species origins.

Modulation of trehalase activity in Saccharomyces cerevisiae by an intrinsic protein

The regulation of cytosolic trehalase activity in yeast has been described as cycles of activation by phosphorylation by cAMP protein kinase. In this paper, evidence is presented for another regulatory mechanism--the binding of an endogenous inhibitory protein. This negative modulator was isolated during the purification procedure of cytosolic cryptic trehalase from repressed wild-type cells of Saccharomyces cerevisiae. However, in derepressed cells the inhibitor was not found nor was it present in ras2 mutant cells submitted to a heat treatment. The trehalase inhibitory activity proved to be a calmodulin ligand protein and, therefore, involved in the modulation of trehalase activity by Ca2+ ions.

Characterization of trehalase activities from the thermophilic fungus Scytalidium thermophilum

The thermophilic fungus Scytalidium thermophilum produced large amounts of intracellular and extracellular trehalase activity when grown on starch as the sole carbon source. The specific activity of the purified proteins: 1700 U (mg protein)-1 (extracellular) and 3700 U (mg protein)-1 (intracellular), was many times higher than the values reported for other microbial sources. The apparent molecular mass of the native enzymes was estimated to be 370 kDa (extracellular trehalase) and 398 kDa (intracellular trehalase) by gel-filtration chromatography. Analysis by SDS-PAGE showed unique polypeptide bands of approx. 82 kDa (extracellular trehalase) and 85 kDa (intracellular trehalase), suggesting that the native enzymes were composed of five subunits. The carbohydrate content of extracellular and intracellular trehalases was estimated to be 81% and 51%, respectively. Electrofocusing indicated a pI of 3.7 and 3.4, respectively, for the extracellular and intracellular enzymes. Both trehalases were highly specific for trehalose and were stimulated by calcium and manganese. Calcium and manganese also protected both trehalases from thermoinactivation. Inhibition was observed in the presence of aluminium, mercurium, copper, zinc, EDTA, ADP, and ATP. Apparent Km values, for the extracellular and intracellular trehalases, were 3.58 mM and 2.24 mM, respectively. The optimum of pH for the extracellular and the intracellular trehalase was 6.0, and the optimum of temperature 60 degrees C and 65 degrees C, respectively.

Characterisation of an acid trehalase of Saccharomyces cerevisiae present in trehalase-sucrase aggregate

An acid trehalase-sucrase aggregate was purified (by 780-fold) from Saccharomyces cerevisiae, following conventional protein purification techniques, to an apparent yield of 18.5%. The aggregate was electrophoretically homogeneous but contained 175, 90, 68, 60, 40 molar mass (kDa) bands on SDS-electrophoresis. The purified aggregate had a specific activity (acid trehalase) of 22 U/mg; a Km value of 5.0 mM but contained 3-times more sucrase activity. Only sucrose and trehalose were hydrolysed by this aggregate and both activities were inhibited by acetate or phosphate. Temperature and pH optima for trehalose hydrolysis appeared to be 40-45 degrees C and 5.0, respectively. The purified aggregate appeared to be disaggregating spontaneously resulting in inactivation of both enzymes, which was enhanced either at pH 3.5 or at pH 7.0. Separation of acid trehalase from the aggregate by hydrophobic interaction chromatography resulted in inactivation. Rechromatography (HPGPLC) of the purified aggregate also gave disaggregation as well as inactivation of both enzymes. Disaggregated acid trehalase and sucrase contained 20-fold and 13-fold lower specific activities, respectively, and appeared to be unstable. Based on these observations we suggest that acid trehalase is stabilised by aggregation with sucrase.

Trehalase in the spermatophore from the bean-shaped accessory gland of the male mealworm beetle, Tenebrio molitor: purification, kinetic properties and localization of the enzyme

Trehalase from the bean-shaped accessory glands of the male mealworm beetle, Tenebrio molitor, was purified by acid treatment, with subsequent chromatography on columns of DEAE-cellulofine and Sephacryl S-300. The molecular masses of the native and the denatured forms were estimated to be 43 and 62 kDa by gel filtration and SDS-PAGE, respectively, an indication that the trehalase may be composed of a single polypeptide. The optimum pH of the reaction catalyzed by trehalase was 5.6-5.8. The Km for trehalose was 4.4 mmol.1(-1). Immunohistochemical experiments with trehalase-specific antiserum showed that the enzyme was localized in one specific type of secretory cell in the bean-shaped accessory gland epithelium and within the semisolid secretory mass that was a precursor to the wall of spermatophore. SDS-PAGE and immunoblotting analysis revealed the presence of a polypeptide of about 62 kDa in the spermatophore. Immunohistochemical observations showed that the trehalase was located at the outgrowth in the anterior portion of the spermatophore. When a fresh spermatophore was immersed in phosphate-buffered saline it discharged sperm in the same manner as in the bursa copulatrix of the female. Before the rupture of the expanded bulb of the spermatophore, almost all of the trehalase had dissolved in the phosphate-buffered saline. The addition of validoxylamine A to the saline, a specific inhibitor of trehalase, did not affect the expansion and evacuation of the spermatophore. These results demonstrate that trehalase, synthesized by a specific type of secretory cell in the bean-shaped accessory gland epithelium, is actively passed into the lumen of the bean-shaped accessory gland and then incorporated into the spermatophore. Trehalase appears to be one of the structural proteins of the spermatophore, although the possibility can not yet be completely ruled out that the trehalase-trehalose system functions for the nourishment and/or activation of the sperm in the bursa copulatrix of the female.

Comparative study of two trehalase activities from Fusarium oxysporum var. lini

Acid and neutral trehalase activities (optimum pH of 4.6 and 6.8, respectively) from Fusarium oxysporum var. lini were studied separately through partial isolation by ammonium sulfate precipitation followed by ion-exchange chromatography on DEAE-Sephacel for neutral enzyme, or using some of their differential properties. Acid activity was unaffected by 1 mM of Ca2+, Mg2+, Mn2+, Ba2+, or EDTA. Contrarily, the neutral enzyme was activated by Ca2+ with an apparent Ka of 0.15 mM; was inhibited by EDTA, Zn2+, Hg2+, or Mg(2+)-ATP; and showed an increase in activity by the raise of buffer ionic strength or by the addition of 100 mM KCl. Acid and neutral enzymes have, respectively, an apparent optimum temperature of 45 and 30 degrees C, an apparent Km for trehalose of 0.43 and 8.45 mM, and an apparent M(r) of 160,000 and 100,000 (by glycerol gradient ultracentrifugation). Acid trehalase was specifically inhibited by acetate buffer and more stable at 50 degrees C than the neutral enzyme. Neutral enzyme exhibited a pI of 6.2 by isoelectric focusing. Contrary to neutral trehalases from other fungi, the enzyme from Fusarium oxysporum var. lini was not activated in crude extract by treatment with Mg(2+)-ATP in the presence of cAMP and not inactivated by alkaline phosphatase from Escherichia coli.

Differential extraction of N-acetylglucosaminidase and trehalase from the cell envelope of Candida albicans

Dithiothreitol (DTT) extraction of N-acetylglucosaminidase and trehalase from intact Candida albicans ATCC 10261 cells was monitored as an index of cell envelope porosity during N-acetylglucosamine-induced morphogenesis. Trehalase, which is secreted into the cell envelope during starvation and bud-formation, displayed similar extraction kinetics in starved, germ tube-forming, and bud-forming cells, indicating that the mother cell wall remains largely unchanged during morphogenic outgrowth and that the porosity of bud and mother cell walls is similar. N-acetylglucosaminidase, which is secreted specifically during morphogenesis, was released eightfold more rapidly from germ tube-forming than bud-forming cells, reflecting major differences in porosity between bud and germ tube. In addition, by assaying DTT extracts and extracted cell residues, it was found that the total extracellular N-acetylglucosaminidase activity increased 2- to 2.5-fold during DTT treatment. Thus, DTT unmasks a cryptic form of N-acetylglucosaminidase. The cryptic activity was associated with the cell wall fraction.

Purification and some properties of a trehalase from a green alga, Lobosphaera sp

An unicellular green alga identified as Lobosphaera sp. by morphological observations was selected as a source of trehalase. The alga grew well heterotrophically and produced intracellular trehalase using Polypepton, yeast extract, and glycerol as nutrients. The enzyme was highly purified by ammonium sulfate fractionation, column chromatography on DEAE-Toyopearl, Sepharose CL-4B, and SP-Toyopearl. The molecular mass was estimated to be 400 kDa by gel filtration. SDS-PAGE indicated that the enzyme consisted of two subunits with a molecular mass range of 180-220 kDa and it contained carbohydrates. The enzyme was most active at pH 5.5 and at 65 degrees C and stable between pH 4-9 and below 65 degrees C. Fe3+ inactivated the enzyme. Sucrose was a competitive inhibitor with a Ki of 7.5 mM. The enzyme specifically hydrolyzed trehalase with a Km of 0.6 mM.

Periplasmic trehalase from Escherichia coli--characterization and immobilization on spherisorb

1. Trehalase was partially purified from Escherichia coli and characterized. The Km for trehalose was 0.78 mM, the pH optimum 5.5 and the temperature optimum 30 degrees C. 2. Trehalase represented approximately 50% of the total protein released by osmotic shock. The preparation was free of nonspecific carbohydrate hydrolases, which act on sucrose, galactose and maltose, permitting trehalose determination in biological samples, such as insect hemolymph and free cell extracts among others. 3. The enzyme was stable in 50 mM maleate buffer, pH 6.2, at -8 degrees C for at least 6 months and could be used to determine trehalose in the range of 6 to 30 nmol. 4. Immobilization of the enzyme was achieved by covalent linkage to spherisorb-5NH2 (spherical silica gel). Retention of total catalytic activity averaged 32%. 5. The reactor, stored for one month at -5 degrees C, retained 98% of its initial immobilized activity. 6. This immobilized form of the enzyme could be used routinely for specific determinations of trehalose.

Molecular activation of a trehalase purified from the fat body of a coleopteran insect (Tenebrio molitor), by an endogenous insulin-like peptide

Trehalase is the major factor involved in the release of glucose in the various insects organs. During physiological regulatory processes, and particularly during the induction or breaking of diapause, insulin-like factors are involved. Then, by contrast with the classical hypoglycemic role of insulin, the insulin-like peptide isolated from the insect (brain and/or fat body) is also able to activate the fat body trehalase in vitro, through a direct molecular interaction. The mechanism involves the binding of the activator to the "trehalase-trehalose complex", rather than on the free enzyme, without change in the Hill coefficient nor in the maximum velocity (Vmax). The rate constant KR is conversely proportional to the activator concentration. This mechanism can be totally quenched by adding an anti-serum anti-insulin-like factor in the reaction medium.

Purification and properties of the soluble midgut trehalase from the gypsy moth, Lymantria dispar

The midgut trehalase (THA) from fifth instar Lymantria dispar (gypsy moth) larvae was purified to homogeneity by two separate methods: gel filtration followed by Rotofor preparative IEF, and affinity chromatography on trehalose coupled to Sepharose 6B followed by preparative polyacrylamide gel electrophoresis. Midgut THA from the last stadium L. dispar larvae existed mainly in soluble form and displayed a single band of activity in nondenaturing polyacrylamide gels when stained by a THA-specific staining procedure. Analytical IEF of purified midgut THA revealed a single protein band with an apparent pI of 4.6. SDS-PAGE and gel permeation studies indicated that the smallest active form of THA in the late fifth instar larval midgut was a monomeric protein with an approximate size of 60 kDa. A specific activity of 67 units/mg of protein at 30 degrees C and at pH 6.4 was determined for the enzyme purified by affinity chromatography and preparative gel electrophoresis. The midgut enzyme exhibited a very high substrate specificity with a Km of 0.4 mM for trehalose. The enzyme was maximally active at pH 5.4-6.0 and was thermally stable at temperatures up to 65 degrees C. The midgut THA was insensitive to inhibition by a high concentration of Tris, sucrose, p-nitrophenyl-beta-D-glucoside or phloridzin. Divalent cations metal ions, hypertrehalosaemic hormone and octopamine had no significant effect on the activity of the purified enzyme in vitro. The purified enzyme was inactivated by modification with DEP and was competitively inhibited by castanospermine with an apparent Ki of 0.8 x 10(-6)M at pH 6.4.

The interaction of Saccharomyces cerevisiae trehalase with membranes

Plasma membranes isolated from cells of Saccharomyces cerevisiae previously submitted to a heat-shock showed a 10-fold increase in membrane-bound trehalase activity. Trehalase was purified to a high specific activity and was shown to be inhibited by glucose 6-phosphate and by the addition of a neutral phospholipid-like surfactant. Purified trehalase binds spontaneously to egg phosphatidylcholine small unilamellar vesicles, when in its active, phosphorylated form. When the enzyme was treated with alkaline phosphatase no binding was observed. The significance of this reversible binding for the control of trehalose metabolism in yeast cells is still unknown.

Assay of trehalose with acid trehalase purified from Saccharomyces cerevisiae

An enzymatic end-point assay of trehalose using acid trehalase from yeast is described. After quantitative hydrolysis of trehalose by acid trehalase, the resulting glucose is assayed with the commercially available glucose oxidase/peroxidase dye system. Pre-existing glucose is determined in a control reaction from which acid trehalase is omitted. When intact cells are analysed for trehalose, pre-existing glucose can be washed out with ice-cold water without reducing the trehalose content of the cells. A convenient method for extraction of trehalose from intact yeast cells is heating for 20 min at 95 degrees C followed by centrifugation. The specificity of the assay is determined by the specificity of the acid trehalase preparation used. As described previously (Mittenbühler, K. and Holzer, H., 1988, J. Biol. Chem. 263, 8537-8543; Mittenbühler, K., 1988, Thesis, University of Freiburg), the following sugars and sugar derivatives do not form glucose when incubated with purified acid trehalase: sucrose, cellobiose, mellobiose, raffinose, maltose, lactose, glucose-6-phosphate, glucose-1-phosphate, galactose. The application of the new trehalose assay to yeast cells grown to different growth stages and at various temperatures is presented.

Purification, cDNA cloning and northern blot analysis of trehalase of pupal midgut of the silkworm, Bombyx mori

Trehalase (alpha-glucoside-1-glucohydrolase, EC 3.2.1.28) was purified from silkworm pupal midgut to homogeneity by DEAE-Sepharose CL-6B and hydroxyapatite chromatography, and native gel electrophoresis. The enzyme had a molecular mass of 70 kDa. The N-terminal amino-acid sequence of the intact trehalase and its three fragments by V8 proteinase digestion was determined. Based on the amino-acid sequence, degenerate oligonucleotides were synthesized and used as primers in a polymerase chain reaction (PCR). Using a 0.8 kb PCR product as a hybridization probe, trehalase clones were isolated from the pupal midgut cDNA library. Sequence analysis revealed that the isolated trehalase cDNA contains 3103 nucleotides and comprises 579 amino acids, including a cleavable signal sequence and five potential N-glycosylation sites. Northern blot analysis clearly showed a 3.0 kb transcript in midgut, and Malpighian tubule, but not in fat body, silk gland, ovary, trachea, brain and suboesophageal ganglion.

A transfer membrane method for in situ detection and quantification of trehalase

A method for the detection and quantification of trehalase activity (EC 3.2.1.28) by immobilization to a membrane support has been developed. Protein samples partly enriched for porcine and Galleria mellonella wax moth larvae trehalase activities were fractionated by polyacrylamide gel electrophoresis, followed by electrophoretic transfer to PVDF membranes, and incubated in a solution containing trehalose (20 mg/ml), glucose oxidase (40 U/ml), phenazine methosulfate (0.06 mg/ml), and nitro blue tetrazolium (0.24 mg/ml) in 20 mM sodium phosphate buffer, pH 6.5. The intensity of the red-colored bands, developed directly on the membrane, was quantified using a computing, laser densitometer and shown to be linearly proportional to the original enzyme activity in extracts determined by liquid assay. The temperature inactivation profile of wax moth trehalase was measured. Alteration of the electrophoresis sample buffer composition further revealed the presence of putative trehalase isoforms in wax moth larval extracts whose relative levels of activity were altered during the course of starvation and infection with Tipula iridescent virus.

Fractionation of renal brush border membrane proteins with Triton X-114 phase partitioning

Analysis of brush border membrane proteins by gel electrophoresis has revealed a complex polypeptide composition. We have investigated the use of Triton X-114 phase partitioning to fractionate such proteins on the basis of their degree of hydrophobicity. Each of the fractions was composed of a complex but distinct set of proteins. Most proteins were solubilized by Triton X-114 and partitioned into the detergent-poor fraction. Trehalase, gamma-glutamyl transpeptidase, and leucine aminopeptidase were well solubilized (greater than 80%) and enriched 5.1-, 3.9-, and 2.5-fold in the detergent-rich fraction. In contrast, alkaline phosphatase and 5'-nucleotidase were poorly solubilized. The specific activities of these enzymes were increased 2.7- and 2.3-fold in the insoluble protein fraction. Maltase was almost completely solubilized and partitioned into the detergent-poor fraction with a small enrichment factor (1.3). These results suggest that Triton X-114 phase partitioning could be useful as a first step in the purification of many brush border membrane proteins.

Purification and properties of an extracellular conidial trehalase from Humicola grisea var. thermoidea

An extracellular trehalase (alpha, alpha-trehalose glucohydrolase, EC 3.2.1.28) was purified from conidia of Humicola grisea var. thermoidea. The purified enzyme is a glycoprotein and migrates as a single polypeptide band during polyacrylamide gel electrophoresis under non-denaturing conditions. The apparent molecular weight of the enzyme was estimated as 580,000 by gel filtration chromatography. The enzyme is separable into three polypeptide bands of 105,000, 98,000 and 84,000 daltons on SDS-PAGE. It is specific for trehalose and its activity is not inhibited by other disaccharides. It has a Km of 2.3 mM, an optimum pH of 5.6 in sodium acetate buffer and a temperature optimum of 60 degrees C. The enzyme is activated by Ca2+, Co2+ and Mn2+ and inhibited by inorganic phosphate, AMP, ADP or ATP. The inhibitory effect of phosphate, AMP and ADP, but not that of ATP, was abolished in the presence of Ca2+.

Partial purification and characterization of trehalase from axenically grown myxamoebae of Dictyostelium discoideum

Lysosomal trehalase from the myxamoebae of Dictyostelium discoideum has been partially purified. The behavior of the enzyme under different chromatographic and electrophoretic conditions reveals its close similarities to other lysosomal enzymes that have been studied earlier. The cellular trehalase, which is electrophoretically homogeneous, appears as two peaks of activity when subjected to hydroxyapatite and gel filtration chromatography. The enzyme has isoelectric points of 4.0 and less than 2.5. Among natural disaccharides tested, the purified trehalase showed absolute specificity for trehalose with an apparent Km of 1.15 mM. However, the enzyme efficiently utilized the synthetic sugar alpha-D-glucosyl fluoride as a substrate. Various methods were employed to estimate the apparent molecular weight, which was found to lie in the range of 30-162 kDa.

Rabbit small intestinal trehalase. Purification, cDNA cloning, expression, and verification of glycosylphosphatidylinositol anchoring

alpha,alpha-Trehalase (EC 3.2.1.28), an intrinsic protein of intestinal brush-border membranes, was purified to homogeneity from rabbits. Partial amino acid sequences were determined. Two degenerate oligonucleotides based on the sequence of a CNBr peptide were employed in a polymerase chain reaction to amplify a 71-base pair fragment of trehalase DNA with rabbit intestine cDNA as a starting template. This fragment was used as a hybridization probe to isolate full length trehalase clones from a rabbit intestine cDNA bank. Sequence analysis revealed that trehalase comprises 578 amino acids, contains at the amino terminus a typical cleavable signal sequence, at the carboxyl terminus a rather hydrophobic region typical of proteins anchored via glycosylphosphatidylinositol, and four potential N-glycosylation sites. Trehalase has no sequence homologies with other sequenced brush-border glycosidases. Northern blot analysis revealed a 1.9-kilobase trehalase mRNA in small intestine and kidney, smaller amounts in liver, and none in lung. Southern blot analysis indicated the gene has a length of 20 kilobase pairs or less. Injection into Xenopus laevis oocytes of mRNA synthesized in vitro from a trehalase template resulted in the expression of trehalase activity several hundredfold above background. The trehalase activity was membrane-bound and could be solubilized upon digestion with phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis. This strongly suggests that rabbit small intestinal trehalase is anchored via glycosylphosphatidylinositol also when expressed in X. laevis oocytes.

Purification and characterization of neutral trehalase from the yeast ABYS1 mutant

Neutral trehalase was purified from stationary yeast ABYS1 mutant cells deficient in the vacuolar proteinases A and B and the carboxypeptidases Y and S. The purified electrophoretically homogeneous preparation of phosphorylated neutral trehalase exhibited a molecular mass of 160,000 Da on nondenaturing gel electrophoresis and of 80,000 Da on sodium dodecyl sulfate-gel electrophoresis. Maximal activity (114 mumol of trehalose min-1 x mg-1 at 37 degrees C) was observed at pH 6.8-7.0. The apparent Km for trehalose was 34.5 mM. Among seven oligosaccharides studied, the enzyme formed glucose only from trehalose. Neutral trehalase is located in the cytosol. A polyclonal rabbit antiserum raised against neutral trehalase precipitates the enzyme in the presence of protein A. The antiserum does not react with acid trehalase. Dephosphorylation by alkaline phosphatase from Escherichia coli of the active phosphorylated enzyme is accompanied by greater than or equal to 90% inactivation. Rephosphorylation by incubation with the catalytic subunit of beef heart protein kinase is accompanied by reactivation and incorporation of 0.85 mol of phosphate/mol subunit (80,000 Da). The phosphorylated amino acid residue was identified as phosphoserine.

Determination of trehalose in biological samples by a simple and stable trehalase preparation

A three step purification procedure for trehalase from Saccharomyces cerevisiae with a recovery of 76% of the original activity is presented. The enzyme was activated by a heat shock treatment prior to homogenization of the cells. A mutant strain deleted in SUC genes was used to avoid contamination by invertase. The lyophylized enzyme was stable for, at least, 5 months and could be used to determine trehalose in the range 25 to 500 nmol. The preparation was free of inspecific phosphatases allowing for trehalose determinations in yeast cell free extracts and in insect hemolymph.

Purification and characterization of acid trehalase from the yeast suc2 mutant

Acid trehalase was purified from the yeast suc2 deletion mutant. After hydrophobic interaction chromatography, the enzyme could be purified to a single band or peak by a further step of either polyacrylamide gel electrophoresis, gel filtration, or isoelectric focusing. An apparent molecular mass of 218,000 Da was calculated from gel filtration. Polyacrylamide gel electrophoresis of the purified enzyme in the presence of sodium dodecyl sulfate suggested a molecular mass of 216,000 Da. Endoglycosidase H digestion of the purified enzyme resulted after sodium dodecyl sulfate gel electrophoresis in one distinct band at 41,000 Da, representing the mannose-free protein moiety of acid trehalase. The carbohydrate content of the enzyme was 86%. Amino acid analysis indicated 354 residues/molecule of enzyme including 9 cysteine moieties and only 1 methionine. The isoelectric point of the enzyme was estimated by gel electrofocusing to be approximately 4.7. The catalytic activity showed a maximum at pH 4.5. The activity of the enzyme was not inhibited by 10 mM each of HgCl2, EDTA, iodoacetic acid, phenanthrolinium chloride or phenylmethylsulfonyl fluoride. There was no activation by divalent metal ions. The acid trehalase exhibited an apparent Km for trehalose of 4.7 +/- 0.1 mM and a Vmax of 99 mumol of trehalose min-1 X mg-1 at 37 degrees C and pH 4.5. The acid trehalase is located in the vacuoles. The rabbit antiserum raised against acid trehalase exhibited strong cross-reaction with purified invertase. These cross-reactions were removed by affinity chromatography using invertase coupled to CNBr-activated Sepharose 4B. Precipitation of acid trehalase activity was observed with the purified antiserum.

In vitro loss of hydrophobicity of trehalase from the brush border membrane of rabbit kidney cortex

Trehalase solubilized with 0.5% Triton X-100 and 0.5% deoxycholate from the brush border membrane of rabbit kidney cortex was all adsorbed on phenyl-Sepharose equilibrated with elution buffer containing no detergents, and all the adsorbed enzyme was eluted in one peak on the addition of 0.5% Triton X-100 to the elution buffer, in contrast to the results reported by Nakano and Sacktor (J. Biochem. 97, 1329-1335 (1985], who separated two forms of trehalase differing in hydrophobicity from rabbit kidney. On concentration of detergent-solubilized extracts, followed by incubation at 37 degrees C, however, there appeared trehalase nonadsorbable on phenyl-Sepharose, i.e. a hydrophilic trehalase. Various protease inhibitors added to the concentrated extracts did not inhibit this conversion at all. The concentration-incubation treatment also increased the proportion of trehalase that interacts with Con A-Sepharose. These results indicate that kidney trehalase that interacts with Con A-Sepharose. These results indicate that kidney trehalase is susceptible to some lytic action of a factor(s) intrinsic to the brush border membrane (limited autolysis), as seen with rabbit intestinal trehalase (Yokota et al., (1986) Biochim. Biophys. Acta 881, 405-414). Therefore, in studies of the molecular form of trehalase (and other proteins) in the brush border membrane of the kidney and intestine where a lot of hydrolases exist, it is very important to take account of limited autolysis which results in some chemical modifications without affecting enzymatic activity.

Rat intestinal trehalase. Studies of the active site

Rat intestinal trehalase was solubilized, purified and reconstituted into proteoliposomes. With octyl glucoside as the solubilizing detergent, the purified protein appeared as a single band on SDS/polyacrylamide-gel electrophoresis with an apparent molecular mass of 67 kDa. Kinetic studies indicated that the active site of this enzyme can be functionally divided into two adjacent regions, namely a binding site (with pKa 4.8) and a catalytic site (with pKa 7.2). Other findings suggested that the catalytic site contains a functional thiol group, which is sensitive to inhibition by N-ethylmaleimide, Hg2+ and iodoacetate. Substrate protection and iodoacetate labelling of the thiol group demonstrated that only a protein of 67 kDa was labelled. Furthermore, sucrose and phlorizin protected the thiol group, but Tris-like inhibitors did not. Structure-inhibition analysis of Tris-like inhibitors, the pH effect of Tris inhibition and Tris protection of 1-(3-dimethylaminopropyl)-3-ethylcarbodi-imide inactivation permitted characterization and location of a separate site containing a carboxy group for Tris binding, which may also be the binding region. On the basis of these findings, a possible structure for the active site of trehalase is proposed.

Purification and properties of detergent-solubilized pig kidney trehalase

Trehalase (alpha, alpha-trehalase, EC 3.2.1.28) was solubilized from the brush border membrane of pig kidney cortex by Triton X-100 and sodium deoxycholate in the presence of inhibitors of proteolytic enzymes. The kidney enzyme was purified 3060-fold using gel filtration, ion exchange chromatography, Con A-Sepharose chromatography, phenyl-Sepharose CL-4B hydrophobic interaction chromatography, Tris-Sepharose 6B affinity chromatography, and hydroxylapatite chromatography. Tris-Sepharose 6B was utilized to absorb contaminant proteins. Purity was estimated as 99% or greater, based on amino-terminal amino acid analysis. The purified enzyme had a specific activity of 278 units/mg protein, showed one major band after silver staining, and had an estimated molecular weight of 80,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme was a glycoprotein and contained 2 mol of glucosamine per mole of trehalase. Kidney trehalase was inhibited by Tris, HgCl2, and phlorizin with Ki values of 3.8 mM, 11 microM, and 2.4 mM, respectively. Inclusion of Cl- in the reaction mixture protected the enzyme from inactivation by HgCl2. The apparent Km for trehalose was calculated to be 2.1 mM. Kidney trehalase was highly specific for trehalose and exhibited an optimal pH of 5.9. The isoelectric point was between pH 4.7 and 4.4, as measured by chromatofocusing.

The use of a monoclonal antibody for the rapid purification of kidney neutral endopeptidase ("enkephalinase") solubilized in octyl glucoside

The neutral endopeptidase ("enkephalinase") of the rabbit brush border membrane has been purified to homogeneity by a rapid immunoaffinity method using a monoclonal antibody. In contrast with other methods used so far, a complete extraction of enkephalinase from the brush border membrane can be achieved with octyl glucoside, without loss of activity. The solubilized enzyme can be selectively separated from the other proteins in a single step using an immunoaffinity column consisting of the monoclonal antibody covalently linked to Sepharose CL-4B. It is demonstrated that enkephalinase can then be recovered in an active form by elution at low pH. The purified enzyme obtained by this method is completely inhibited by thiorphan and appears as a single 94,000 dalton protein after polyacrylamide gel electrophoresis under denaturing and reducing conditions.

Partial purification and characterization of the interconvertible forms of trehalase from Saccharomyces cerevisiae

Cryptic trehalase from Saccharomyces cerevisiae was purified about 3000-fold. The recovery of 970% of the original "activity" indicated the removal of an inhibitor of the enzyme. Active trehalase, obtained through phosphorylation of cryptic trehalase by cAMP-dependent protein kinase, was isolated by chromatography on DEAE-cellulose. A major phosphorylated protein, with an apparent Mr of 86,000, was detected after SDS-polyacrylamide gel electrophoresis. This protein band correlated exactly with the elution profile of trehalase activity and 32Pi incorporation into the enzyme on DEAE-cellulose chromatography. Partially purified active trehalase showed absolute specificity towards trehalose with an apparent Km of 4.79 X 10(-3) M. Both forms of the enzyme showed an apparent molecular weight of 160,000, by gel filtration. Centrifugation on a glycerol density gradient indicated multiple forms of trehalase-c, with Mr of 320,000, 160,000, and 80,000. After activation of each of these forms by protein kinase, a single form of trehalase-a was observed, with a Mr of 160,000. Trehalase-c appears to be a totally inactive form of the enzyme. The only mechanism of activation seems to be phosphorylation by cAMP-dependent protein kinase. When the protein kinase concentration was varied, at a fixed trehalase-c concentration, a sigmoidal activation plot was obtained. This result suggests the occurrence of multiple forms of cryptic trehalase.

Identification of larval and adult Simulium yahense and Simulium sanctipauli based on species-specific enzyme markers and their distribution at different breeding habitats in Central Liberia

Human-biting adults and late instar larvae of the Simulium damnosum complex from four ecologically different simuliid breeding habitats in the Firestone Rubber Plantation at Harbel, Liberia, were identified morphologically and the monthly species composition of each site was recorded. Samples of the predominant species found at each site were assayed electrophoretically for species-specific variants of phosphoglucomutase (PGM) and trehalase (TRE). Enzyme identifications of flies and larvae were compared with morphological identifications to determine the accuracy of field identifications relying upon morphological characters. Enzyme identifications confirmed the accuracy of over 98% of the adult female identifications. S. yahense was found to be the predominant human-biting species at each site over the 10 months of sampling, with S. sanctipauli comprising a small percentage of the biting fly population. Species-specific larval enzymes confirmed the accuracy of more than 96% of the larval identifications. S. yahense was the predominant larval species found in smaller, more shaded, cooler breeding waters, while S. sanctipauli predominated in the single large watercourse that was sampled. Normally allopatric, mixed populations of these two larval species were found to exist at all sites, but sympatry occurred primarily during the wet season months of May-October. Biting activity of S. sanctipauli was found to be greatest during wet season months, and generally reflected the increase of S. sanctipauli in the larval populations of habitats dominated by S. yahense. The low human-biting activity of S. sanctipauli at all sites and during times which fostered large populations of S. sanctipauli larvae may be an indication of this specie's zoophilic tendency. Circumstantial evidence of hybridization, the expression of PGM and TRE species-specific variants for both species, was found in adults and larvae morphologically identified as S. yahense. The frequency of this "hybrid" condition, based upon PGM and TRE, was calculated to be comparable to the frequency of hybridization as determined by larval chromosome inversions.

Comparative study of two trehalases from Candida utilis

Candida utilis ATCC 60459 contains two intracellular trehalase enzymes clearly distinguishable by molecular weight, behaviour in ion-exchange chromatography and kinetic properties. The high molecular weight trehalase (500 kDa trehalase) is specifically inhibited by acetate and accounts for less than 30% of the total trehalase activity found in cell extracts. The smaller trehalase (280 kDa trehalase) exists mostly as a cryptic enzyme whose activity can be postranslationally activated by cAMP-dependent phosphorylation. The enzyme activity of the 280 kDa trehalase is strongly inhibited by Zn2+ and markedly enhanced in the presence of Ca2+ and Mn2+. The activation by these cations, contrariwise to that induced by ATP and cAMP, does not imply a covalent modification of the 280 kDa enzyme. Several parameters have been determined for both enzymes. The 280 kDa enzyme has the properties shown by the so-called regulatory trehalases whereas the 500 kDa enzyme presents characteristics of a nonregulatory type of trehalase.

Purification and characterization of amphiphilic trehalase from rabbit small intestine

Rabbit intestinal trehalase (alpha,alpha-trehalose glucohydrolase, EC 3.2.1.28) was solubilized with Triton X-100 and purified in the presence of EDTA. The purified enzyme was homogeneous on polyacrylamide gel electrophoresis in the presence of Triton X-100 or SDS. It showed amphiphilic properties on gel filtration. polyacrylamide gel electrophoresis, charge-shift electrophoresis and phenyl-Sepharose chromatography. Its molecular weight was estimated to be about 330 000 by gel filtration under nondenaturing conditions and in the presence of Triton X-100, the value being in satisfactory agreement with the sum of the weight of one Triton X-100 micelle and twice the molecular weight (105 000) of purified hydrophilic trehalase which had been deprived of the anchor segment. The two purified trehalases gave almost the same molecular weights (about 75 000) on SDS-polyacrylamide gel electrophoresis. These results suggest that intestinal trehalase consists of two subunits with a molecular weight of 75 000 and that its anchor segment is small (less than 5000). Triton X-100 extracts freshly prepared from intestinal microvilli essentially showed one form of trehalase, which behaved on phenyl-Sepharose and Con A-Sepharose chromatography in the same manner as purified amphiphilic trehalase.