Metabolism of resorcinylic compounds by bacteria: orcinol pathway in Pseudomonas putida.

Enrichment cultures yielded two strains of Pseudomonas putida capable of growth with orcinol (3,5-dihydroxytoluene) as the sole source of carbon. Experiments with cell suspensions and cell extracts indicate that orcinol is metabolized by hydroxylation of the benzene ring followed successively by ring cleavage and hydrolyses to give 2 mol of acetate and 1 mol of pyruvate per mol of orcinol as shown: orcinol leads to 2,3,5-trihydroxytoluene leads to 2,4,6-trioxoheptanoate leads to acetate + acetylpyruvate leads to acetate + pyruvate. Evidence for this pathway is based on: (i) high respiratory activities of orcinol-grown cells towards 2,3,5-trihydroxytoluene; (ii) transient accumulation of a quinone, probably 2-hydroxy-6-methyl-1,4-benzoquinone, during grouth with orcinol; (iii) formation of pyruvate and acetate from orcinol, 2,3,5-trihydroxytoluene, and acetylpyruvate catalyzed by extracts of orcinol, but not by succinate-grown cells; (iv) characterization of the product of oxidation of 3-methylcatechol (an analogue of 2,3,5-trihydroxytoluene) showing that oxygenative cleavage occurs between carbons bearing methyl and hydroxyl substituents; (v) transient appearance of a compound having spectral properties similar to those of acetylpyruvate during 2,3,5-trihydroxytoluene oxidation by extracts of orcinol-grown cells. Orcinol hydroxylase exhibits catalytic activity when resorcinol or m-cresol is substituted for orcinol; hydroxyquinol and 3-methylcatechol are substrates for the ring cleavage enzyme 2,3,5-trihydroxytoluene-1,2-oxygenase. The enzymes of this pathway are induced by growth with orcinol but not with glucose or succinate.     

The distinctiveness of ATP:citrate lyase from Aspergillus nidulans

ATP:citrate lyase (ACL), an important enzyme in lipid synthesis, has been purified from Aspergillus nidulans to a specific activity of 19.6 micromol min(-1) mg(-1), almost twice that of any other purified ACL and shown to be distinct from any previously purified ACL. The enzyme is a 371+/-31 kDa hexamer of 3 alpha, 3 beta proteins, unlike the 4 alpha tetramer found in rats or yeasts. The molecular weights of the alpha and beta protein subunits were determined by SDS-PAGE to be 70 and 55 kDa.ACL in A. nidulans (unlike Aspergillus niger) appears to be regulated by the carbon source present in the media. In crude extracts, it was found at high activity (88 micromol min(-1) mg protein(-1)) in glucose-grown cells but only at low activity (10 micromol min(-1) mg protein(-1)) in acetate-grown cells.     

Characterization and carbon metabolism in fungi pathogenic to Triatoma infestans, a chagas disease vector

The pathogenicity of Metarhizium anisopliae (Ma) and Beauveria bassiana (Bb) isolates against Triatoma infestans, the major vector of Chagas disease in Argentina is reported. A 100% mortality was achieved with mean lethal times varying form 5.8 (Ma6) to 7.7 (Bb5) or 11.1 days (Bb10). The fatty acid, hydrocarbon, and total lipid patterns were compared for glucose-grown and alkane-grown Bb10 cultures. The alkane-grown cells showed a lipid pattern different from that of glucose-grown cells, with triacylglyercol as the major lipid fraction, whereas sterols prevailed in the glucose-grown cells. A significant reduction in the relative amounts of linoleic acid diminished the unsaturated/saturated fatty acid ratio for alkane-grown cells; in addition, large amounts of heptacosanoic and eicosanoic acids were detected in the saturated fraction. The hydrocarbon profile of Bb10 showed a saturated chain length distribution,with a marked prevalence for straight chains, ranging from n-C18 to n-C37 in the carbon skeleton, with n-C22 as the major component. Alkane-grown cells showed no qualitative changes in their hydrocarbon fraction, but a similar ratio for odd/even carbon chains. After 48-h incubation assays,[1-(14)C]acetate uptake was largely diminished following a period of alkane growth induction. Glucose-grown cells readily incorporated 19% of the labelinto phospholipids, hydrocarbons, triacylglycerols, and free fatty acids. In contrast, incorporation was reduced to 5.3% for alkane-grown cells, accounting only for phospholipid synthesis.     

Presence of lactate dehydrogenase and lactate racemase in Megasphaera elsdenii grown on glucose or lactate.

Activity of D-lactate dehydrogenase (D-LDH) was shown not only in cell extracts from Megasphaera elsdenii grown on DL-lactate, but also in cell extracts from glucose-grown cells, although glucose-grown cells contained approximately half as much D-LDH as DL-lactate-grown cells. This indicates that the D-LDH of M. elsdenii is a constitutive enzyme. However, lactate racemase (LR) activity was present in DL-lactate-grown cells, but was not detected in glucose-grown cells, suggesting that LR is induced by lactate. Acetate, propionate, and butyrate were produced similarly from both D- and L-lactate, indicating that LR can be induced by both D- and L-lactate. These results suggest that the primary reason for the inability of M. elsdenii to produce propionate from glucose is that cells fermenting glucose do not synthesize LR, which is induced by lactate.     

Pyrimidine nucleotide synthesis in Pseudomonas citronellolis

Pyrimidine biosynthesis was active in Pseudomonas citronellolis ATCC 13674 and appeared to be regulated by pyrimidines. When wild-type cells were grown on succinate in the presence of uracil, the de novo enzyme activities were depressed while only four enzyme activities were depressed in the glucose-grown cells. On either carbon source, orotic acid-grown cells had diminished aspartate transcarbamoylase, dihydroorotase or OMP decarboxylase activity. Pyrimidine limitation of glucose-grown pyrimidine auxotrophic cells resulted in de novo enzyme activities, except for transcarbamoyolase activity, that were elevated by more than 5-fold compared to their activities in uracil-grown cells. Since pyrimidine limitation of succinate-grown mutant cells produced less enzyme derepression, catabolite repression appeared to be a factor. At the level of enzyme activity, aspartate transcarbamoylase activity in P. citronellolis was strongly inhibited by all effectors tested. Compared to the regulation of pyrimidine biosynthesis in taxonomically-related species, pyrimidine biosynthesis in P. citronellolis appeared more highly regulated.     

Partial Purification of Isocitrate Lyase from Candida tropicalis and Some Kinetic Properties of the Enzyme

Isocitrate lyase was purified partially from n-alkane-grown cells and glucose-grown cells of Candida tropicalis by means of ammonium sulfate fractionation and DEAE-cellulose column chromatography. The preparation from alkane-grown cells showed one peak of the enzyme activity, while that from glucose-grown cells showed two distinct peaks of the activity, on DEAE-cellulose column chromatography. These enzymes, having the similar pH optima (around 7.0) and Km values with dl-isocitrate (1.2 ~ 1.7 mm), were inhibited by various metabolic intermediates, such as 6-phosphogluconate and phosphoenolpyruvate.

Time-course changes in the activities of isocitrate lyase and isocitrate dehydrogenases of C. tropicalis during the growth indicated that the lyase would participate preferentially in alkane assimilation and NAD-linked isocitrate dehydrogenase in glucose utilization of the yeast.

Regulation of isocitrate metabolism in C. tropicalis through glyoxylate cycle and tricarboxylic acid cycle is discussed based on the kinetic properties, cellular localization and time- course changes in the levels of isocitrate lyase and NAD-linked and NADP-linked isocitrate dehydrogenases.     

Synthesis and properties of new photoactivable derivatives of tetrodotoxin

Eight lots of reagent-grade phenol from four companies were tested for capacity to interact with Cu2+ to produce an inactivator or inactivators of the transfective RNA obtained from poliovirions; such capacity to interact with Cu2+ is referred to as cofactor activity. Six of the lots showed cofactor activity; two did not. A review of the data on the phenol lots and of the properties of the impurity or impurities conferring cofactor activity suggested that the active impurity(ies) might be a dihydric or trihydric phenol. Commercial catechol, resorcinol, hydroquinone, orcinol and pyrogallol were tested and found active. The activity of hydroquinone was outstandingly high. Upon serial recrystallization, the activity of catechol, hydroquinone, orcinol and pyrogallol remained constant, but the activity of resorcinol decreased markedly, in stepwise fashion, showing the most of the activity of the commercial resorcinol was due to impurity(ies). Each of catechol, hydroquinone, orcinol, pyrogallol, and the commercial resorcinol was shown to react with Cu2+ to produce inactivator(s). The effective target for inactivator(s) was the RNA and not the transfection process. The kinetics of inactivator(s) production varied for the different phenols, and the inactivator activity of the incubated mixture of pyrogallol and Cu2+ was notably labile.     

Regulation of phosphatidylcholine biosynthesis in Saccharomyces cerevisiae

Evidence is presented which indicates that the biosynthesis of phosphatidylcholine by the methylation pathway in growing cultures of Saccharomyces cerevisiae is repressed by the presence of choline in the growth medium. This result, obtained previously for glucose-grown cells, was also observed for lactate-grown cells, of which half of the phosphatidylcholine is mitochondrial. A respiration-deficient mutant of the parent wild-type strain has been studied, and its inability to form functional mitochondria cannot be due to an impaired methylation pathway, as it has been shown to incorporate (14)C-CH(3)-methionine into all of the methylated glycerophosphatides. The incorporation rate is depressed by the inclusion of 1 mm choline in the growth medium, suggesting a regulatory effect similar to that demonstrated for the wild-type strain. The effects of choline on the glycerophospholipid composition of lactate and glucose-grown cells is presented. The repressive effects of the two related bases, mono- and dimethylethanolamine, were examined, and reduced levels of (14)C-CH(3)-methionine incorporation were found for cells grown in the presence of these bases. The effect of choline on the methylation rates is reversible and glucosegrown cells regain the nonrepressed level of methylation activity in 60 to 80 min after removal of choline from the growth medium.     

Evidence for an inducible glucose transport system in Kluyveromyces lactis.

To find the cause of delayed glucose oxidation in succinate-grown Kluyveromyces lactis, glucose transport was studied in glucose- and in succinate-grown cells. The initial rate of 2-deoxyglucose (2-dGlc) accumulation, as well as the appearance of 2-deoxyglucose 6-phosphate, was higher in the glucose-grown cells. In both cell types, 2-dGlc was apparently transported in the free form to be phosphorylated intracellularly. In glucose-grown cells the level of free 2-dGlc in the pool was always less than the external concentration. Exchange transport in starved, poisoned cells loaded with unlabeled 2-dGlc was 140-fold greater in glucose- than in succinate-grown cells, probably beacuse of the presence of an inducible transport component. The development of the increased rate of transport in a succinate-grown uracil-requiring auxotroph after transfer to glucose depends on the presence of uracil.     

Evidence for an inducible glucose transport system in Kluyveromyces lactis

To find the cause of delayed glucose oxidation in succinate-grown Kluyveromyces lactis, glucose transport was studied in glucose- and in succinate-grown cells. The initial rate of 2-deoxyglucose (2-dGlc) accumulation, as well as the appearance of 2-deoxyglucose 6-phosphate, was higher in the glucose-grown cells. In both cell types, 2-dGlc was apparently transported in the free form to be phosphorylated intracellularly . In glucose-grown cells the level of free 2-dGlc in the pool was always less than the external concentration. Exchange transport in starved, poisoned cells loaded with unlabeled 2-dGlc was 140-fold greater in glucose- than in succinate-grown cells, probably because of the presence of an inducible transport component. The development of the increased rate of transport in a succinate-grown uracil-requiring auxotroph after transfer to glucose depends on the presence of uracil.     

Aliphatic and chlorinated alkenes and epoxides as inducers of alkene monooxygenase and epoxidase activities in Xanthobacter strain Py2.

The inducible nature of the alkene oxidation system of Xanthobacter strain Py2 has been investigated. Cultures grown with glucose as the carbon source did not contain detectable levels of alkene monooxygenase or epoxidase, two key enzymes of alkene and epoxide metabolism. Upon addition of propylene to glucose-grown cultures, alkene monooxygenase and epoxidase activities increased and after an 11-h induction period reached levels of specific activity comparable to those in propylene-grown cells. Addition of chloramphenicol or rifampin prevented the increase in the enzyme activities. Comparison of the banding patterns of proteins present in cell extracts revealed that polypeptides with molecular masses of 43, 53, and 57 kDa accumulate in propylene-grown but not glucose-grown cells. Pulse-labeling of glucose-grown cells with [35S]methionine and [35S]cysteine revealed that the 43-, 53-, and 57-kDa proteins, as well as two additional polypeptides with molecular masses of 12 and 21 kDa, were newly synthesized upon exposure of cells to propylene or propylene oxide. The addition to glucose-grown cells of a variety of other aliphatic and chlorinated alkenes and epoxides, including ethylene, vinyl chloride (1-chloroethylene), cis- and trans-1,2-dichloroethylene, 1-chloropropylene, 1,3-dichloropropylene, 1-butylene, trans-2-butylene, isobutylene, ethylene oxide, epichlorohydrin (3-chloro-1,2-epoxypropane), 1,2-epoxybutane, cis- and trans-2,3-epoxybutane, and isobutylene oxide stimulated the synthesis of the five propylene-inducible polypeptides as well as increases in alkene monooxygenase and epoxidase activities. In contrast, acetylene, and a range of aliphatic and chlorinated alkanes, did not stimulate the synthesis of the propylene-inducible polypeptides or the increase in alkene monooxygenase and epoxidase activities.     

Glucose transport in nongrowing yeast

The inducible, nonenergy-requiring glucose transport system of the yeast Kluyveromyces lactis is inactivated upon starving cells of glucose by (1) transferring logarithmic phase glucose-grown cells to synthetic medium containing a nonglycolytic carbon source, and (2) upon transition of logarithmic phase glucose-grown cells to stationary phase. The steady-state accumulation of nonmetabolizeable 6-deoxyglucose and the apparent $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$ of transport of 6-deoxyglucose is the same in stationary phase cells and in logarithmic phase cells. The rate of transport is lower in the nongrowing cells. Restoration of activity requires energy and protein synthesis as well as inducer.     

Identification and Characterization of Epoxide Carboxylase Activity in Cell Extracts of Nocardia corallina B276

The metabolism of aliphatic epoxides (epoxyalkanes) by the alkene-utilizing actinomycete Nocardia corallina B276 was investigated. Suspensions of N. corallina cells grown with propylene as the carbon source readily degraded propylene and epoxypropane, while suspensions of glucose-grown cells did not. The addition of propylene and epoxypropane to glucose-grown cells resulted in a time-dependent increase in propylene- and epoxypropane-degrading activities that was prevented by the addition of rifampin and chloramphenicol. The expression of alkene- and epoxide-degrading activities was correlated with the high-level expression of several polypeptides not present in extracts of glucose-grown cells. Epoxypropane and epoxybutane degradation by propylene-grown cell suspensions of N. corallina was stimulated by the addition of CO₂ and inhibited by the depletion of CO₂. Cell extracts catalyzed the carboxylation of epoxypropane to form acetoacetate in a reaction that was dependent on the addition of CO₂, NAD⁺, and a reductant (NADPH or dithiothreitol). In the absence of CO₂, epoxypropane was isomerized by cell extracts to form acetone at a rate approximately 10-fold lower than the rate of epoxypropane carboxylation. Methylepoxypropane was found to be a time-dependent, irreversible inactivator of epoxyalkane-degrading activity. These properties demonstrate that epoxyalkane metabolism in N. corallina occurs by a carboxylation reaction forming β-keto acids as products and provide evidence for the involvement in this reaction of an epoxide carboxylase with properties and cofactor requirements similar to those of the four-component epoxide carboxylase enzyme system of the gram-negative bacterium Xanthobacter strain Py2 (J. R. Allen and S. A. Ensign, J. Biol. Chem. 272:32121–32128, 1997). The addition of epoxide carboxylase component I from Xanthobacter strain Py2 to methylepoxypropane-inactivated N. corallina extracts restored epoxide carboxylase activity, and the addition of epoxide carboxylase component II from Xanthobacter Py2 to active N. corallina extracts stimulated epoxide isomerase rates to the same levels observed with the purified Xanthobacter system. Antibodies raised against Xanthobacter strain Py2 epoxide carboxylase component I cross-reacted with a polypeptide in propylene-grown N. corallina extracts with the same molecular weight as component I but did not cross-react with glucose-grown extracts. Together, these results suggest a common pathway of epoxyalkane metabolism for phylogenetically distinct bacteria that involves CO₂ fixation and the activity of a multicomponent epoxide carboxylase enzyme system.     

Glucose-induced Crypticity Toward Succinate Metabolism in Saccharomyces lactis

Saccharomyces lactis grown on glucose adapted very slowly to growth on succinate. This initial inability of glucose-grown cells to grow on succinate was paralleled by their inability to oxidize succinate. The possibility that repression by glucose of respiratory chain components was responsible for these observations was examined. Glucose-grown cells were able to respire glucose, ethyl alcohol, and lactate and were able to initiate growth on ethyl alcohol as rapidly as succinate-grown cells. Respiratory enzyme levels were essentially the same in cells grown on succinate or on glucose. Spectroscopic analysis revealed that glucose-grown cells possessed a full complement of cytochrome bands. Since by these criteria glucose-grown S. lactis appears to possess a competent respiratory system, the penetration of succinate-2,3-(14)C into succinate- and glucose-grown cells was examined directly. Glucose-grown cells exhibited a strong permeability barrier to succinate. Comparison of glucose oxidation by S. lactis and by S. cerevisiae suggests that the crypticity to succinate does not depend upon a strong Crabtree effect in S. lactis.     

Characterization of an inducible citrate uptake system in Penicillium simplicissimum

When citrate was used as a sole source of carbon, citrate uptake by Penicillium simplicissimum increased 267-fold (if glucose-grown mycelium was adapted to citrate) or 1400-fold (if the fungus was grown on citrate) compared to glucose-grown mycelium. Inhibition of macromolecular synthesis prevented this stimulation of citrate uptake. Citrate uptake by glucose-grown mycelium was low (0.0015 nmol min(-1) (mg DW)(-1)) and most probably due to diffusion of undissociated citric acid. Citrate-adapted mycelium had a K(M) of 65 micromol l(-1) and a V(max) of 0.34 nmol min(-1) (mg DW)(-1). In citrate-grown mycelium K(M) was 318 micromol l(-1) and V(max) was 8.5 nmol min(-1) (mg DW)(-1). Citrate uptake was inhibited by sodium azide and uncouplers (TCS, 3,3',4',5-tetrachlorosalicylanilide; FCCP, carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone). Because of this we postulate that the induced citrate uptake must be an active transport process. The pH optimum of citrate uptake was between pH 6 and 7. EDTA and Mg2+, Mn2+, Cu2+, Zn2+, Fe2+, Ca2+ only weakly influenced the induced citrate uptake. The properties of citrate uptake by Aspergillus niger and P. simplicissimum are compared.     

Metabolic analysis of acetate accumulation during xylose consumption by<Emphasis Type="Italic"> Paenibacillus polymyxa</Emphasis>

Paenibacillus polymyxa ATCC 12321 produced more acetic acid and less butanediol from xylose than from glucose. The product yields from xylose were ethanol (0.72 mol/mol sugar), (R,R)-2,3-butanediol (0.31 mol/mol sugar), and acetate (0.38 mol/mol sugar) while those from glucose were ethanol (0.74 mol/mol sugar), (R,R)-2,3-butanediol (0.46 mol/mol sugar), and acetate (0.05 mol/mol sugar). Higher acetate kinase activity and lower acetate uptake ability were found in xylose-grown cells than in glucose-grown cells. Furthermore, phosphoketolase activity was higher in xylose-grown cells than in glucose-grown cells. In fed-batch culture on xylose, glucose feeding raised the butanediol yield to 0.56 mol/mol sugar and reduced acetate accumulation to 0.04 mol/mol sugar.     

Acetyl-coenzyme-A carboxylase of Candida lipolytica. 2. Regulation of cellular content and synthesis of the enzyme.

The level of acetyl-coenzyme-A carboxylase activity in Candida lipolytica undergoes large variations depending upon the carbon source on which the yeast is grown. Cells grown on n-alkanes or fatty acids exhibit a lower activity level than do cells grown on glucose. Among the n-alkanes and fatty acids tested, n-heptadecane, n-octadecane, oleic acid and linoleic acid reduce the enzyme activity to the lowest levels, which are 16-18% of the activity level in glucose-grown cells. Immunochemical titrations and Ouchterlony double-diffusion analysis with specific antibody as well as kinetic studies have indicated that the observed decrease in the level of acetyl-CoA carboxylase activity is due to a reduction in the cellular content of the enzyme. Furthermore, isotopic leucine incorporation studies with the use of the immunoprecipitation technique have demonstrated that the relative rate of synthesis of the enzyme in oleic-acid-grown cells is diminished to 12% of that in glucose-grown cells. Evidence has also been obtained to support the view that the enzyme in this yeast is not degraded at a rate high enough to contribute to the marked decrease in the cellular content of the enzyme. Thus, it is concluded that the reduction in acetyl-CoA carboxylase content in fatty-acid-grown cells is due to diminished synthesis of the enzyme.     

A shift to 50°C provokes death in distinct ways for glucose- and oleate-grown cells of <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis>

Based on the observation that shocks provoked by heat or amphiphilic compounds present some similarities, this work aims at studying whether cells grown on oleate (amphiphilic pre-stress) acquire a tolerance to heat shock. In rich media, changing glucose for oleate significantly enhanced the cell resistance to the shock, however, cells grown on a minimal oleate medium lost their ability to grow on agar with the same kinetic than glucose-grown cells (more than 7-log decrease in 18 min compared with 3-log for oleate-grown cells). Despite this difference in kinetics, the sequence of events was similar for oleate-grown cells maintained at 50°C with a (1) loss of ability to form colonies at 27°C, (2) loss of membrane integrity and (3) lysis (observed only for some minimal-oleate-grown cells). Glucose-grown cells underwent different changes. Their membranes, which were less fluid, lost their integrity as well and cells were rapidly inactivated. But, surprisingly, their nuclear DNA was not stained by propidium iodide and other cationic fluorescent DNA-specific probes but became stainable by hydrophobic ones. Moreover, they underwent a dramatic increase in membrane viscosity. The evolution of lipid bodies during the heat shock depended also on the growth medium. In glucose-grown cells, they seemed to coalesce with the nuclear membrane whereas for oleate-grown cells, they coalesced together forming big droplets which could be released in the medium. In some rare cases of oleate-grown cells, lipid bodies were fragmented and occupied all the cell volume. These results show that heat triggers programmed cell death with uncommon hallmarks for glucose-grown cells and necrosis for methyl-oleate-grown cells.