Trehalose metabolism in dormant and activated spores of Phycomyces blakesleeanus Burgeff

Evidence is obtained for the existence of two different localizations of trehalase (,-trehalose glucohydrolase, EC 3.2.1.28) in Phycomyces spores: one inside the cell, and one in the periplasmic region. The latter enzyme is sensitive to 0.1 mol l^-1 HCl treatment and its activity can be regulated by external pH changes. The periplasmic form of the enzyme is involved in the metabolism of added labelled trehalose. This sugar is hydrolyzed externally to glucose which is found mainly in the incubation medium and which is partly absorbed by the spores. During incubation trehalose leaks out from both dormant and activated spores and is subsequently hydrolyzed to glucose. The intracellular trehalase is probably involved in the breakdown of endogenous trehalose in spores. After heat activation the hydrolysis of endogenous trehalose is stimulated even without an important increase in activity of intracellular trehalase. Additional treatments which break dormancy of spores without a significant activation of trehalase are the following: heating of HCl-treated spores and treatment of spores with reducing substances (e.g. Na₂S₂O₄ and NaHSO₃).     

α-Glucosidase activity in haemolymph of the American cockroach, Periplaneta americana

α-Glucosidase activity of whole haemolymph has been investigated in adult males of the American cockroach, Periplaneta americana. Two electrophoretically distinguishable enzymes capable of hydrolysing α-glucosidic linkages are present in the serum component of the haemolymph, and one of these hydrolyses trehalose. Trehalase activity is also present in haemocytes, and the haemocyte enzyme shares an identical electrophoretic mobility and similar pH sensitivity with the serum trehalase. Furthermore, both enzymes are inhibited to the same extent by sodium ethylene diamine tetracetate (EDTA); thus it is suggested that the same enzyme may be responsible for trehalase activity in the two components. The K_m of EDTA-inhibited trehalase is 3·3 mM and this value is reduced to 1·8 mM upon activation of the enzyme by calcium ions. The properties of the trehalase are discussed in light of the possible rôle of the enzyme in regulating haemolymph trehalose and glucose concentrations.     

Role of periplasmic trehalase in uptake of trehalose by the thermophilic bacterium Rhodothermus marinus

Trehalose uptake at 65°C in Rhodothermus marinus was characterized. The profile of trehalose uptake as a function of concentration showed two distinct types of saturation kinetics, and the analysis of the data was complicated by the activity of a periplasmic trehalase. The kinetic parameters of this enzyme determined in whole cells were as follows: K_m = 156 ± 11 μM and V_max = 21.2 ± 0.4 nmol/min/mg of total protein. Therefore, trehalose could be acted upon by this periplasmic activity, yielding glucose that subsequently entered the cell via the glucose uptake system, which was also characterized. To distinguish the several contributions in this intricate system, a mathematical model was developed that took into account the experimental kinetic parameters for trehalase, trehalose transport, glucose transport, competition data with trehalose, glucose, and palatinose, and measurements of glucose diffusion out of the periplasm. It was concluded that R. marinus has distinct transport systems for trehalose and glucose; moreover, the experimental data fit perfectly with a model considering a high-affinity, low-capacity transport system for trehalose (K_m = 0.11 ± 0.03 μM and V_max = 0.39 ± 0.02 nmol/min/mg of protein) and a glucose transporter with moderate affinity and capacity (K_m = 46 ± 3 μM and V_max = 48 ± 1 nmol/min/mg of protein). The contribution of the trehalose transporter is important only in trehalose-poor environments (trehalose concentrations up to 6 μM); at higher concentrations trehalose is assimilated primarily via trehalase and the glucose transport system. Trehalose uptake was constitutive, but the activity decreased 60% in response to osmotic stress. The nature of the trehalose transporter and the physiological relevance of these findings are discussed.     

A continuous coupled polarographic assay for trehalase.

A continuous, coupled polarographic assay, which couples trehalose hydrolysis to O₂ consumption using glucose oxidase (EC 1.1.3.4) and catalase (EC 1.11.1.6) as ancillary enzymes has been developed for the measurement of trehalase (α-α′-trehalose 1-d-glucohydrolase, EC 3.2.1.28) activity. With this procedure, O₂ consumption was a linear function of time and the coupled reaction rate was directly proportional to the amount of protein assayed with both crude and partially purified enzyme preparations. The limits of sensitivity with this assay correspond to the production of 2.5 nmol of glucose/min. The validity of this assay was confirmed by comparative studies with a discontinuous colorimetric assay for the quantitation of glucose. In addition, the applicability of this assay was appraised by determining the K_m of the enzyme for trehalose. The value obtained with the polarographic assay (i.e., 1.3 ± 0.1 mm trehalose) showed excellent agreement with that obtained using a discontinuous colorimetric method (i.e., 1.2 mm trehalose). Thus the equivalence and applicability studies with the polarographic assay demonstrated that this procedure is a valid and sensitive method for the rapid quantitation of trehalase activity.     

Purification and characterization of trehalose phosphorylase from the commercial mushroom Agaricus bisporus

Trehalose phosphorylase (EC 2.4.1.64) from Agaricus bisporus was purified for the first time from a fungus. This enzyme appears to play a key role in trehalose metabolism in A. bisporus since no trehalase or trehalose synthase activities could be detected in this fungus. Trehalose phosphorylase catalyzes the reversible reaction of degradation (phosphorolysis) and synthesis of trehalose. The native enzyme has a molecular weight of 240 kDa and consists of four identical 61-kDa subunits. The isoelectric point of the enzyme was pH 4.8. The optimum temperature for both enzyme reactions was 30°C. The optimum pH ranges for trehalose degradation and synthesis were 6.0–7.5 and 6.0–7.0, respectively. Trehalose degradation was inhibited by ATP and trehalose analogs, whereas the synthetic activity was inhibited by P_i (K_i=2.0 mM). The enzyme was highly specific towards trehalose, P_i, glucose and α-glucose-1-phosphate. The stoichiometry of the reaction between trehalose, P_i, glucose and α-glucose-1-phosphate was 1:1:1:1 (molar ratio). The K_m values were 61, 4.7, 24 and 6.3 mM for trehalose, P_i, glucose and α-glucose-1-phosphate, respectively. Under physiological conditions, A. bisporus trehalose phosphorylase probably performs both synthesis and degradation of trehalose.     

The properties of trehalase from the mosquito-parasitizing water mold, Lagenidum sp

The soluble trehalase from the phycomycete Lagenidium sp., a parasite of many species of mosquitoes, was purified by acid titration, acetone precipitation, and Sephadex G-200 chromatography to give a 170-fold increase in specific activity over the crude extract. The enzyme was specific for trehalose. A β-glucosidase was copurified with the trehalase, but did not interfere with its characterization. Lagendium trehalase had a K_m of 1.43 mm, and E_a of 11.4 kcal/mole, and a pH of optimum activity of 5.5–6.5, and a molecular weight of 72,000. It was denatured by 30 min incubation at temperatures above 50°C, severely inhibited by heavy metals, and competitively inhibited by sucrose. No other reported inhibitors, including mannitol and ATP, were effective. Suggested physiological roles for the enzyme include the breakdown of stored trehalose in the mycelium and zoospores, and the digestion of hemolymph trehalose in infected mosquito larvae.     

Trehalose absorption related with trehalase in developing ovaries of the silkworm,Bombyx mori

Summary The mechanism of trehalose absorption was examined in developing ovaries of the silkworm,Bombyx mori. Trehalose and glucose absorption followed saturation kinetics giving an apparentK _m value of 8.4 mM and a V_max of 12.5 moles/30 min per g ovaries for trehalose absorption, and an apparentK _m value of 26.4 mM and a V_max of 36.6 moles/30 min per g ovaries for glucose uptake. Trehalose absorption was clearly inhibited by addition of NaCN or NaN₃ to the incubation medium.Cellobiose, maltose, sucrose and turanose were taken up by ovaries at much lower rates than trehalose. Among the disaccharidases which hydrolyse these sugars, trehalase activity was highest. The correlation between trehalase activity and trehalose absorption rate was also demonstrated by a reduction of trehalase activity accompanied by reduced absorption rates after extirpation of the suboesophageal ganglion (SG). During trehalose absorption, glucose was released into the incubation medium, but after SG removal, no liberation of glucose was observed. Furthermore, no accumulation of¹⁴C-trehalose, added to the medium, was observed in the cells and almost all radioactivity was recovered as glucose and glycogen in the ovaries.These results suggest that in developing silkworm ovaries, trehalose is absorbed by a specific carriermediated and energy-dependent system, in which the hydrolysis by trehalase is an obligatory step.     

Evidence that a glucose-mediated rise in cyclic AMP triggers germination ofPilobolus longipes spores

Spores ofPilobolus longipes incubated in phosphate buffer were activated within 5–10 min following the addition of either glucose or 6-deoxyglucose. Cyclic AMP content increased in response to glucose or 6-deoxyglucose, and the increase consistently preceded spore activation. Dibutyryl cyclic AMP also caused activation. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) did not cause activation, but, when added to spores with a suboptimal level of 6-deoxyglucose, it amplified the signal to produce a large increase in activation. IBMX increased intracellular cyclic AMP levels when it was applied with 6-deoxyglucose, but had no effect when it was applied alone. Phosphodiesterase activities in cell extracts from dormant and activated spores were not significantly different. These results indicate that the rise in cyclic AMP that follows exposure to glucose may play an important role in triggering spore germination.     

The mechanism by which 2-deoxyglucose inhibits glucose-induced activation of Pilobolus longipes spores

Sporangiospores of Pilobolus longipes were activated by either glucose, 6-deoxyglucose, or derivatives of cyclic AMP. Cyclic AMP content increased after the addition of either glucose or 6-deoxyglucose and the increase preceded spore activation, indicating that glucose triggers germination via cyclic AMP. Activation, whether induced by glucose, 6-deoxyglucose, or cyclic nucleotides was inhibited by 2-deoxyglucose. However, cyclic AMP levels also increased after the addition of 2-deoxyglucose. Radioactive 2-deoxyglucose was recovered from spores mainly as 2-deoxyglucose 6-phosphate, suggesting that phosphorylation of 2-deoxyglucose may inhibit spore activation by trapping ATP. Support for the hypothesis came from ATP assays which showed that 2-deoxyglucose reduced intracellular ATP to undetectable levels. Moreover, when ATP levels were restored with exogenous fructose, 2-deoxyglucose was no longer inhibitory but was then an effective germination trigger.     

Influence of octopamine or trehalase activity in muscle and hemolymph of the American cockroach, Periplaneta americana L.

Injection of adult male cockroaches (Periplaneta americana) with 10 μl 1 μM octopamine causes elevated activity of trehalase (α,α-trehalose glucohydrolase; EC 3.2.1.28) in hemolymph and muscle but not in gut. Tyramine, dopamine and glutamate, at the same concentration, failed to elicit any effect on trehalase activity. Determination of some kinetic parameters for muscle and hemolymph trehalase reveal that octopamine causes an increase in V_max without any significant alteration in the K_m of the enzyme for trehalose. The results are discussed in terms of the physiological significance of octopamine-mediated activation of tissue trehalase.     

Cyclic AMP regulation of glucose transport in germinating Pilobolus longipes spores

Pilobolus longipes spores were activated by either glucose or 6-deoxyglucose. Glucose-induced spore activation was previously shown to follow an increase in intracellular cyclic AMP. Concurrent with glucose-induced spore activation, were shifts in 6-deoxyglucose transport kinetics towards higher V _max and K _m values. Cyclic AMP derivatives also caused spore activation and similar changes in the kinetic parameters of 6-deoxyglucose transport. The time course of activation was paralleled by changes in transport activity. Inhibition of phosphodiesterase alone did not cause activation or induce changes in transport activity, but in combination with sub-optimal levels of either 6-deoxyglucose or cAMP derivatives, it amplified the germination signals to produce large increases in both spore activation and 6-deoxyglucose transport activity. These results support the conclusion that glucose transport in germinating spores is regulated by cAMP.Abbreviations IBMX 3-isobutyl-1-methylxanthine; monobutyryl cyclic AMP - N⁶ monobutyryladenosine 3:5-cyclic monophosphate - 8-bromo cyclic AMP 8-bromoadenosine 3:5-cyclic monophosphate     

Degradation of the compatible solute trehalose in Ectothiorhodospira halochloris: isolation and characterization of trehalase

Trehalase, which hydrolyzes the disaccharide trehalose to -d-glucose was isolated and partially purified (124-fold) from the phototrophic halo-alkaliphilic bacterium Ectothiorhodospira halochloris. The molecular mass was determined to be 480,000 and the isoelectric point pH 5.6. Temperature optimum was found to be 40°C and the pH-optimum 7.8–8.1. In spite of its high K _m-value of 0.5 M, trehalase of E. halochloris was shown to be specific for trehalose. Trehalase is activated by phosphate which is, however, not involved in the reaction mechanism. The enzyme is activated by the compatible solute betaine and inhibited by salts. In the presence of betaine the K _m-value is lowered from 0.5 M to 0.16 M; moreover, betaine partially protects enzymatic activity from salt inhibition. The findings indicate that betaine might regulate the trehalose level in the cells by affecting trehalase activity.     

A highly thermostable trehalase from the thermophilic bacterium <Emphasis Type="Italic">Rhodothermus marinus</Emphasis>

Trehalases play a central role in the metabolism of trehalose and can be found in a wide variety of organisms. A periplasmic trehalase (α,α-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°C and pH 6.5. The recombinant trehalase exhibited a K _m of 0.16 mM and a V _max of 81 μmol of trehalose (min)⁻¹ (mg of protein)⁻¹ at the optimal temperature for growth of R. marinus (65°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.     

Biochemical characterization of neutral trehalase activity in Saccharomyces boulardii

Lyophilized cells of the non-pathogenic yeast Saccharomyces boulardii are used in many countries for the treatment of several types of diarrhoea and other gastrointestinal diseases. Although the cells must be viable, their mechanism of action is unknown. The disaccharide trehalose is a protectant against several forms of environmental stress in yeast and is involved in maintaining cell viability. There is no information on the enzymes involved in degradation of trehalose in S. boulardii. The aim of the present study was to characterize trehalase activity in this yeast. Cells of S. boulardii grown in glucose exhibited neutral trehalase activity only in the exponential phase. Acidic trehalase was not detected in glucose medium. Cells grown in trehalose exhibited acid and neutral trehalase activities at all growth stages, particularly in the exponential phase. The optimum pH and temperature values for neutral trehalase activity were determined as 6.5 and 30 °C respectively, the half-life being approximately 3 min at 45 °C. The relative molecular mass of neutral trehalase is 80 kDa and the K _m 6.4 mM (±0.6). Neutral trehalase activity at pH 6.5 was weakly inhibited by 5 mM EDTA and strongly inhibited by ATP, as well as the divalent ions Cu⁺⁺, Fe⁺⁺ and Zn⁺⁺. Enzyme activity was stimulated by Mg⁺⁺ and Ca⁺⁺ only in the absence of cAMP. The presence of cAMP with no ion additions increased activity by 40%. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cloning, expression and functional characterization of a novel trehalose synthase from marine Pseudomonas sp. P8005

Trehalose synthase (TreS) catalyzes the reversible interconversion of maltose and trehalose. A novel treS gene with a length of 3,369 bp, encoding a protein of 1,122 amino acid residues with a predicted molecular mass of 126 kDa, was cloned from a marine Pseudomonas sp. P8005 (CCTCC: M2010298) and expressed in Escherichia coli. The amino acid sequence identities between this novel TreS and other reported TreS is relatively low. The purified recombinant TreS showed an optimum pH and temperature of 7.2 and 37 °C, respectively. The enzyme displayed a high conversion rate (70 %) of maltose to trehalose during equilibrium and had a higher catalytic efficiency (k _cat/K _m) for maltose than for trehalose, suggesting its application in the production of trehalose. In addition to maltose and trehalose, this enzyme can also act on sucrose, although this activity is relatively low. Mutagenesis studies demonstrated that enzymatic activity was reduced dramatically by individually substitution with alanine for D78, Y81, H121, D219, E261, H331 or D332, which implied that these residues might be important in P8005-TreS. Experiments using isotope-labeled substrates showed that [²H₂]trehalose combined with unlabeled trehalose was converted to [²H₂]maltose and maltose, but without any production of [²H]maltose or [²H]trehalose and with no incorporation of exogenous [²H₇]glucose into the disaccharides during the conversion catalyzed by this enzyme. This finding indicated the involvement of an intramolecular mechanism in P8005-TreS catalyzing the reversible interconversion of maltose and trehalose.     

Extracellular trehalose utilization by Saccharomyces cerevisiae

Two haploid strains of Saccharomyces cerevisiae viz. MATα and MATa were grown in glucose and trehalose medium and growth patterns were compared. Both strains show similar growth, except for an extended lag phase in trehalose grown cells. In both trehalose grown strains increase in activities of both extracellular trehalase activities and simultaneous decrease in extracellular trehalose level was seen. This coincided with a sharp increase in extracellular glucose level and beginning of log phase of growth. Alcohol production was also observed. Secreted trehalase activity was detected, in addition to periplasmic activity. It appeared that extracellular trehalose was hydrolyzed into glucose by extracellular trehalase activity. This glucose was utilized by the cells for growth. The alcohol formation was due to the fermentation of glucose. Addition of extracellular trehalase caused reduction in the lag phase when grown in trehalose medium, supporting our hypothesis of extracellular utilization of trehalose.     

Human trehalase is a stress responsive protein in Saccharomyces cerevisiae

Three trehalases ATH1, NTH1, and NTH2 have been identified in Saccharomyces cerevisiae. ATH1, and NTH1 hydrolyze trehalose to glucose to provide energy and assist in recovery from stress. Human trehalase (TREH) is expressed in the intestine and kidney and probably hydrolyzes ingested trehalose in the intestine and acts as marker of renal tubular damage in kidney. Since trehalose is not present in circulation or kidney tubules, its renal effect suggests it has other yet unidentified actions. Here we examined the function of human trehalase in budding yeast. We constructed three yeast trehalase mutants (NTH1Δ, NTH2Δ, and ATH1Δ) and then transformed TREH into these mutants. NTH1Δ did not grow on media containing trehalose as the carbon source, and TREH did not rectify NTH1Δ dysfunction and also did not grow on trehalose medium, suggesting that TREH is not responsible for utilization of exogenous trehalose in yeast. In experiments involving exposure to heat, osmotic and oxidative stresses, NTH1Δ showed no recovery. Interestingly, ATH1Δ-TREH showed high sensitivity to all three stressors. ATH1Δ and NTH2Δ showed very low neutral trehalase activity and NTH1Δ did not show any neutral trehalase activity, and trehalose concentrations were higher. Increased neutral trehalase activity (equivalent to the wild type), reduction of trehalose content and brisk sensitivity to stressors were noted in TREH-ATH1Δ strain, but not in TREH-NTH1Δ or -NTH2Δ. Our results suggest that TREH acts as a stress-response protein in the kidney rather than involved in utilization of exogenous trehalose.     

Enhanced freeze tolerance of baker’s yeast by overexpressed trehalose-6-phosphate synthase gene (TPS1) and deleted trehalase genes in frozen dough

Several recombinant strains with overexpressed trehalose-6-phosphate synthase gene (TPS1) and/or deleted trehalase genes were obtained to elucidate the relationships between TPS1, trehalase genes, content of intracellular trehalose and freeze tolerance of baker’s yeast, as well as improve the fermentation properties of lean dough after freezing. In this study, strain TL301_TPS1 overexpressing TPS1 showed 62.92 % higher trehalose-6-phosphate synthase (Tps1) activity and enhanced the content of intracellular trehalose than the parental strain. Deleting ATH1 exerted a significant effect on trehalase activities and the degradation amount of intracellular trehalose during the first 30 min of prefermentation. This finding indicates that acid trehalase (Ath1) plays a role in intracellular trehalose degradation. NTH2 encodes a functional neutral trehalase (Nth2) that was significantly involved in intracellular trehalose degradation in the absence of the NTH1 and/or ATH1 gene. The survival ratio, freeze-tolerance ratio and relative fermentation ability of strain TL301_TPS1 were approximately twice as high as those of the parental strain (BY6-9α). The increase in freeze tolerance of strain TL301_TPS1 was accompanied by relatively low trehalase activity, high Tps1 activity and high residual content of intracellular trehalose. Our results suggest that overexpressing TPS1 and deleting trehalase genes are sufficient to improve the freeze tolerance of baker’s yeast in frozen dough. The present study provides guidance for the commercial baking industry as well as the research on the intracellular trehalose mobilization and freeze tolerance of baker’s yeast.     

Cyclic AMP regulation of fructose metabolism in germinatingPilobolus longipes spores

DormantPilobolus longipes spores metabolized fructose primarily to ethanol, CO₂, and trehalose. Cyclic AMP-induced spore activation was accompanied by a large stimulation of glycolytic activity. Mobilization of reserves, which was cyclic AMP dependent, accounted for a portion of the glycolytic product. The remaining product was derived from exogenous fructose. Increases in both fructose transport activity and hexose 6-phosphate levels were associated with 6-deoxyglucose-induced spore activation. Phosphofructokinase-1 activity in spore extracts was almost totally dependent upon fructose, 2,6-bisphosphate. High fructose 2,6-bisphosphate levels were correlated with rapid fructose metabolism. However, fructose alone caused a rise in fructose 2,6-bisphosphate content (sufficient to fully stimulate phosphofructokinase-1 activity) but there was no concurrent stimulation of glycolysis. These results suggest that glycolytic rates are determined mainly by hexose 6-phosphate levels and that cyclic AMP regulation of transport is an important determinant of hexose 6-phosphate concentration.     

Metabolism of endogenous trehalose by Streptomyces griseus spores and by spores or cells of other actinomycetes.

The disaccharide trehalose is accumulated as a storage product by spores of Streptomyces griseus. Nongerminating spores used their trehalose reserves slowly when incubated in buffer for several months. In contrast, spores rapidly depleted their trehalose pools during the first hours of germination. Extracts of dormant spores contained a high specific activity of the enzyme trehalase. The level of trehalase remained relatively constant during germination or incubation in buffer. Nongerminating spores of Streptomyces viridochromogenes, Streptomyces antibioticus, and Micromonospora echinospora and nongrowing spherical cells of Arthrobacter crystallopoietes and Nocardia corallina also maintained large amounts of trehalose and active trehalase. These trehalose reserves were depleted during spore germination or outgrowth of spherical Arthrobacter and Nocardia cells into rods.