Purification and Properties of Acetate Kinase from Acholeplasma laidlawii

Acetate kinase (EC 2.7.2.1) was purified from Acholeplasma laidlawii cytoplasm by a combination of ammonium sulfate fractionation, gel filtration, diethylaminoethyl-cellulose chromatography, and affinity chromatography on 8-(6-aminohexylamino)-adenosine 5'-triphosphate conjugated to Sepharose 4B. The enzyme was composed of polypeptide chains of about 50,000 molecular weight as estimated from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Under nondenaturating conditions, apparent molecular weights between 64,000 and 130,000 were obtained, depending upon mainly the ionic strength of the test solution. The enzyme had a narrow specificity for phosphate acceptor acids, whereas both purine and pyrimidine nucleoside triphosphates were suitable phosphate donors. Na(+) and K(+) inhibited both acetyl phosphate and adenosine 5'-triphosphate synthesis, and the latter was also inhibited by high concentrations of adenosine 5'-diphosphate and acetyl phosphate. This substrate inhibition was partially abolished by 0.5 M NaCl. The enzyme catalyzed the independent adenosine 5'-diphosphate<-->adenosine 5'-triphosphate and acetate<-->acetyl phosphate exchanges. The rate of the latter was enhanced by the addition of cosubstrate Mg(2+)-adenosine 5'-triphosphate. The high affinity for substrates, except for acetate, indicated that under physiological conditions the direction of the enzymic reaction favors adenosine 5'-triphosphate synthesis. Thus, a mechanism for adenosine 5'-triphosphate generation in mycoplasmas is suggested.     

Three deoxyribonucleic acid-dependent adenosine triphosphatases from Bacillus subtilis.

We have isolated from Bacillus subtilis three deoxyribonucleic acid (DNA)-dependent adenosine triphosphatases (ATPases) (gamma-phosphohydrolases). The enzymes were extensively purified, and their physicochemical and functional properties were determined. The three enzymes (ATPases I, II, and III) were shown to be different by several criteria. ATPases II and III showed an absolute requirement for single-stranded DNA as a cofactor, whereas ATPase I had some residual activity also with double-stranded DNA. They required Mg2+ and had a pH optimum of 6.5 to 7. Only adenosine 5'-triphosphate and deoxyadenosine 5'-triphosphate were hydrolyzed. The molecular weights of ATPases I, II, and III were 108,000, 115,000, and 148,000, respectively. Km values for adenosine 5'-triphosphate and DNA were also evaluated and shown to be different for each enzyme. All three enzymes formed physical complexes with single-stranded DNA. We present evidence that ATPases I and II might migrate along DNA during adenosine 5'-triphosphate hydrolysis. On the other hand, this effect was not observed with ATPase III, which exhibited the highest affinity for single-stranded DNA.     

Adenosine 5'-triphosphate formation in Thiobacillus ferrooxidans vesicles by H+ ion gradients comparable to those of environmental conditions.

Vesicles prepared from iron-grown Thiobacillus ferrooxidans, and subsequently loaded with adenosine 5'-diphosphate and inorganic phosphate, produced adenosine 5'-triphosphate when subjected to H+ gradients comparable to those in the cells' normal environment (i.e., an internal pH in the range of 6.0 to 8.0 with an optimum of 7.0 to 7.8 and an external pH in the range of 2.1 to 4.1 with an optimum of 2.8). Nigericin, dicyclohexylcarbodiimide, and pentachlorophenol decreased adenosine 5'-triphosphate synthesis. Valinomycin at concentrations of 2.5 and 5.0 micrograms/ml increased adenosine 5'-triphosphate formation by 25 and 30%, respectively.     

Genetic recombination in Nocardia mediterranei.

The regulation of macromolecular biosynthesis was studied in a temperature-sensitive mutant of Escherichia coli previously identified as containing a single mutation causing a thermolabile sn-glycerol-3-phosphate acyltransferase, the first enzyme of the pathway for phospholipid biosynthesis. When this mutant was shifted to a nonpermissive temperature, phospholipid synthesis, as well as ribonucleic acid, deoxyribonucleic acid, and protein synthesis, decreased in a coordinate manner, suggesting the existence of a common regulatory mechanism. During the same time that the rate of macromolecular synthesis was decreasing at the nonpermissive temperature, the intracellular concentration of adenosine 5'-triphosphate dropped dramatically and the concentration of adenosine monophosphate increased. The concentration of adenosine 5'-diphosphate dropped, but not as markedly. The decrease in macromolecular synthesis and the changes in the adenine nucleotide concentrations can now be attributed to a thermolabile adenylate kinase. The inactivation of adenylate kinase prevented the cell from converting adenosine 5'-monophosphate to adenosine 5'-diphosphate and consequently from making adenosine 5'-triphosphate. This in turn caused a decrease in the rate of macromolecular synthesis and cell growth. Adenylate kinase, therefore, is a key enzyme in controlling the rate of cell growth. The nature of the possible relationship between adenylate kinase and glycerol-3-phosphate acyltransferase is discussed.     

Histidine starvation and adenosine 5'-triphosphate depletion in chemotaxis of Salmonella typhimurium.

Starvation for histidine prevented tumbling in Salmonella typhimurium hisF auxotrophs, including constantly tumbling strains with an additional mutation in cheB or cheZ. However, histidine-starved cheZs hisF strains were not defective in flagellar function or the tumbling mechanism since freshly starved auxotrophs tumbled in response to a variety of repellents. Tumbling in histidine-starved S. typhimurium could be restored in 13 s by addition of adenine or in 4 min by addition of histidine. Chloramphenicol did not prevent restoration of tumbling by these substances. Assays of adenosine 5'-triphosphate were performed based upon previous demonstration of adenine depletion in hisF auxotrophs starved for histidine. The adenosine 5'-triphosphate concentration dropped rapidly during the course of starvation, falling to less than 5% of the initial level as the cells ceased tumbling entirely. The change to smooth motility was prevented by 2-thiazolealanine, which inhibits phosphoribosyltransferase, thereby preventing adenine depletion during histidine starvation. These results suggest that an adenosine 5'-triphosphate deficiency was responsible for the change in tumbling frequency.     

Effects of growth substrate and respiratory chain composition on bioenergetics in Acinetobacter sp. strain HO1-N.

The relationship between respiratory chain composition and efficiency of coupling phosphorylation to electron transport was examined in Acinetobacter sp. strain HO1-N. Cells containing only cytochrome o as a terminal oxidase displayed the same stoichiometries of adenosine 5'-triphosphate synthesis and proton extrusion as cells which contained both cytochromes o and d as terminal oxidases. In addition, CO inhibition and photo-relief of cytochromes o or d did not alter the efficiency of energy coupling. These findings indicate that adenosine 5'-triphosphate synthesis is coupled to electron transport through both cytochromes o and d in Acinetobacter.     

Some effects of uncouplers and inhibitors on growth and electron transport in rumen bacteria.

Uncouplers and inhibitors of electron transport affected growth and electron transport of rumen bacteria in various ways. Selenomonas ruminantium was not affected by inhibitor and uncoupler concentrations which affected growth and electron transport of Bacteroides ruminicola, B. succinogenes, and Butyrivibrio fibrisolvens. Inhibitors, when active, led to accumulation of reduced electron carriers before the site of action, but differences were found among organisms in the site of action of these inhibitors. Uncouplers reduced the glucose molar growth yields (Ygluc) of B. ruminicola, B. succinogenes, and B. fibrisolvens compared with those obtained without uncouplers. The extent of Ygluc reduction accompanying inhibitor exposure reflected electron transport chain structure. S. ruminantium appeared to obtain its adenosine 5'-triphosphate from substrate-level processes only. The other organisms studied appeared to obtain adenosine 5'-triphosphate both from substrate-level processes and from electron transport but differed in the amount of adenosine 5'-triphosphate obtained from glucose catabolism and in the proportions of adenosine 5'-triphosphate obtained from substrate-level reactions and electron transport.     

Purification, characterization, and regulation of a nicotinamide adenine dinucleotide-dependent lactate dehydrogenase from Actinomyces viscosus.

A nicotinamide adenine dinucleotide-specific L-(+)-lactate dehydrogenase (LDH) (EC 1.11.27) from Actinomyces viscosus T-6-1600 was purified approximately 110-fold by a combination of diethylaminoethyl-cellulose and 0.5 M Agarose A column chromatography. The ldh was stable at 26 C, but was quite labile at temperatures below 5 C. The enzyme had a molecular weight of 100,000 +/- 10,000 as determined by 0.5 M Agarose molecular exclusion chromatography and showed optimum activity between pH 5.5 and 6.2. The A. viscosus LDH exhibited homotropic interactions with its substrate, pyruvate, and its coenzyme, reduced nicotinamide adenine dinucleotide, indicating multiple binding sites on the enzyme for these ligands with some degree of cooperative interaction between them. The enzyme was under negative control by adenosine 5'-triphosphate, and its kinetic response to the negative effector was sigmoidal in nature. Inorganic phosphate reversed the inhibition exerted on the A. viscosus LDH by adenosine. The 5'-triphosphate thermal stability at 65 C of the LDH from A. viscosus was increased in the presence of its negative effector, adenosine 5'-triphosphate, but was markedly decreased in the presence of its coenzyme, reduced nicotinamide adenine dinucleotide. The glycolytic intermediate, fructose-1,6-diphosphate, had no effect on the catalytic activity of the A. viscosus LDH at saturating pyruvate concentrations. However, fructose-1,6-diphosphate was a potent positive effector at low substrate concentrations. Thus the A. viscosus LDH is under positive control by fructose-1,6-diphosphate and inorganic phosphate, but under negative control by adenosine 5'-triphosphate.     

Properties of the Bacillus licheniformis A5 glutamine synthetase purified from cells grown in the presence of ammonia or nitrate.

The glutamine synthetase from Bacillus licheniformis A5 was purified by using a combination of polyethylene glycol precipitation and chromatography on Bio-Gel A 1.5m. The resulting preparation was judged to be homogeneous by the criteria of polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, equilibrium analytical ultracentrifugation, and electron microscopic analysis. The enzyme is a dodecamer with a molecular weight of approximately 616,000, and its subunit molecular weight is 51,000. Under optimal assay conditions (pH 6.6, 37 degrees C) apparent Km values for glutamate, ammonia, and manganese.adenosine 5'-triphosphate (1:1 ratio) were 3.6, 0.4, and 0.9 mM, respectively. Glutamine synthetase activity was inhibited approximately 50% by the addition of 5 mM glutamine, alanine, glycine, serine, alpha-ketoglutarate, carbamyl phosphate, adenosine 5'-diphosphate, or inosine 5'-triphosphate to the standard glutamine synthetase assay system, whereas 5 mM adenosine 5'-monophosphate or pyrophosphate caused approximately 90% inhibition of enzyme activity. Phosphorylribosyl pyrophosphate at 5 mM enhanced activity approximately 60%. We were unable to detect any physical or kinetic differences in the properties of the enzyme when it was purified from cells grown in the presence of ammonia or nitrate as sole nitrogen source. The data indicate that B. licheniformis A5 contains one species of glutamine synthetase whose catalytic activity is not regulated by a covalent modification system.     

Diglyceride kinase in human platelets

Human platelets contain diglyceride kinase, an enzyme that catalyzes the phosphorylation of diacylglycerol by adenosine 5'-triphosphate to yield phosphatidic acid. The majority of the platelet enzyme is particulate-bound, and membrane fractions of platelet homogenates have a higher specific activity than granule fractions. Both deoxycholate and magnesium are necessary for optimal enzyme activity. The K(m) of the enzyme for adenosine 5'-triphosphate is 1.3 mm, and the apparent K(m) for diacylglycerol is 0.4 mm. The pH optimum is 6.6-6.8 in imidazole-HCl or maleate-NaOH buffer. The enzyme activity of platelets from normal subjects was similar to the activity from patients with renal and hepatic failure.     

Multiple forms of cytochrome b in Mycobacterium phlei: kinetics of reduction.

The kinetics of reduction of the b-type cytochromes in the electron transport particles (ETP) from Mycobacterium phlei were studied with nicotinamide adenine dinucleotide, reduced form (NADH) or succinate as electron donors. There appeared to be three active cytochromes b in the ETP,bS563 and bS559, which were reducible by either substrate, and bN563, which was reducible by NADH but not by succinate. In the presence of adenosine 5'-triphosphate, a substantial increase in b563 reduction was observed with succinate at anaerobiosis. This was followed by a decrease in absorption. Adenosine 5'-triphosphate did not effect an increase in cytochrome b563 reduction at transition with NADH, but the occurrence of a secondary decrease in absorption was reflected in a decrease in total enzymatic reduction. The adenosine 5'-triphosphate effect was altered in trypsin-treated ETP, and abolished by uncoupling agents or by removal of the coupling factor-latent adenosine triphosphatase. In the presence of a supernatant fraction obtained during the preparation of the ETP, b563 reduction with succinate was greatly increased. A smaller increase was observed with NADH. Cytochrome b reduction was also studied in ETP inhibited by 2-n-nonylhydroxyquinoline-N-oxide, which appears to inhibit at bS563. On the basis of these data the interrelationships among the b-type cytochromes can be described in relation to the M. phlei electron transport chain.     

Effect of zinc on adenine nucleotide pools in relation to aflatoxin biosynthesis in Aspergillus parasiticus.

The adenylic acid systems of Aspergillus parasiticus were studied in zinc-replete and zinc-deficient media. The adenosine 5'-triphosphate levels of the fungus were high during exponential phase and low during stationary phase in zinc-replete cultures. On the other hand, the levels of adenosine 5'-diphosphate and adenosine 5'-monophosphate were low during exponential phase of growth and high during stationary phase. The adenosine 5'-triphosphate levels during exponential phase may indicate higher primary metabolic activity of the fungus. On the other hand, high adenosine 5'-monophosphate levels during stationary phase may inhibit lipid formation and may enhance aflatoxin levels. The inorganic phosphorus content was low in a zinc-replete medium throughout the growth period, thereby favoring aflatoxin biosynthesis. The energy charge during the exponential phase was high but low during the stationary phase. In general the energy charge values were lower because of high adenosine 5'-monophosphate content.     

Source of energy for the Escherichia coli galactose transport systems induced by galactose

The beta-methyl-galactoside- and galactose-specific transport systems of Escherichia coli were shown by experiments involving inhibitors and the use of an adenosine triphosphatase mutant strain to utilize adenosine 5'-triphosphate or a related compound to drive active transport. These systems were shown to be unable to use the activated-membrane state. The galactose-specific transport system was shown to behave most like a member of the binding-protein class of transport systems by its response to osmotic shock and vesicle formation. These results extended to two sugar transport systems: the correlation between the source of energy and class of transport system found by Berger (1973) for amino acid transport systems. That is, binding-protein systems utilized adenosine 5'-triphosphate whereas membrane-bound systems utilized the activated-membrane state to drive active transport.     

Energetics of Microbacterium thermosphactum in glucose-limited continuous culture.

Microbacterium thermosphactum was grown at 25 degrees C in glucose-limited continuous culture under aerobic (greater than 120 microM oxygen) and anaerobic (less than 0.2 microM oxygen) conditions. The end products of the anaerobic metabolism of glucose were identified as L-lactate and ethanol. Together these compounds accounted for between 85 and 90% of the glucose utilized over the full range of growth rates studied. In addition, 4% of the glucose utilized was incorporated into cellular material. Under anaerobic conditions the molar growth yield was 40 g (dry weight) of cells per mol of glucose utilized, and the maintenance energy coefficient was 0.4 mmol of glucose utilized per g (dry weight) of cells per h. For cells grown under aerobic conditions in the corresponding values were 73 g/mol and 0.2 mmol/g per h, respectively. The molar growth yield with respect to adenosine 5'-triphosphate varied with the growth rate of the culture, and the true molar growth yield with respect to adenosine 5'-triphosphate was found to be 20 g/mol of adenosine 5'-triphosphate.     

Energetics of Microbacterium thermosphactum in glucose-limited continuous culture.

Microbacterium thermosphactum was grown at 25 degrees C in glucose-limited continuous culture under aerobic (greater than 120 microM oxygen) and anaerobic (less than 0.2 microM oxygen) conditions. The end products of the anaerobic metabolism of glucose were identified as L-lactate and ethanol. Together these compounds accounted for between 85 and 90% of the glucose utilized over the full range of growth rates studied. In addition, 4% of the glucose utilized was incorporated into cellular material. Under anaerobic conditions the molar growth yield was 40 g (dry weight) of cells per mol of glucose utilized, and the maintenance energy coefficient was 0.4 mmol of glucose utilized per g (dry weight) of cells per h. For cells grown under aerobic conditions in the corresponding values were 73 g/mol and 0.2 mmol/g per h, respectively. The molar growth yield with respect to adenosine 5'-triphosphate varied with the growth rate of the culture, and the true molar growth yield with respect to adenosine 5'-triphosphate was found to be 20 g/mol of adenosine 5'-triphosphate.     

Adenosine induction of rapid catabolism of adenine ribonucleotides and independent elevation of the ATP content in quiescent mouse fibroblasts

The influence of adenosine on the ribonucleotide metabolism in quiescent BALB/c 3T3 cells was studied. The cellular adenine ribonucleotides were labelled by pretreating the cells with [2-3H]-adenine. After addition of adenosine to the cell cultures, the amount and radioactivity of the cellular purine ribonucleotides and the radioactivity of the purine compounds in the medium were determined. It appeared that adenosine gave rise both to rapid catabolism of adenine ribonucleotides with inosine 5'-monophosphate (IMP) as an intermediate and to expansion of the cellular adenosine 5'-triphosphate (ATP) pool. The maximal rates and the apparent activation constants for the two processes have been determined. Experiments with varying concentrations of coformycin (an inhibitor of adenosine 5'-monophosphate [AMP] deaminase and adenosine deaminase) and of 5'-amino-5'-deoxyadenosine (an inhibitor of adenosine kinase), respectively, showed that each compound may almost completely inhibit the adenosine-induced catabolism. This effect can be obtained under conditions where there was little or no effect by the two inhibitors on the rate of expansion of the cellular ATP pool. These results may best be explained by assuming that the process of expansion of the ATP pool is independent of the induced catabolism of adenine ribonucleotides, even though both processes seem to depend on the phosphorylation of adenosine to AMP. The total increase in the pool size of ATP and of guanosine 5'-triphosphate (GTP), both caused by adenosine, seems not to have regulatory effect on adenine ribonucleotide catabolism.     

Is ATP a substrate for 15-lipoxygenase?

Lipoxygenases catalyze peroxidation of polyunsaturated fatty acids containing the 1-cis, 4-cis pentadiene structure. Linoleic (18:2), linolenic (18:3), and arachidonic (20:4) acids are the predominant substrates for this class of enzymes. Effects of 15-lipoxygenase on the hydrolysis of adenosine 5'-triphosphate were investigated in vitro using soybean lipoxygenase and adenosine 5'-[gamma-32P]triphosphate. The amount of inorganic phosphate released from adenosine 5'-triphosphate was dependent upon enzyme as well as substrate concentrations, pH, and the duration of incubation. The ATPase activity with a Vmax value of 3.3 mumol.mg protein-1.h-1 and a Km value of 5.9 mM was noted in the presence of different concentrations of ATP at pH = 7.4. Phenidone, a lipoxygenase inhibitor, had no effect on this reaction. These findings suggest that soybean lipoxygenase catalyzes the release of inorganic phosphate from ATP primarily via hydrolysis.     

Accumulation of arsenate, phosphate, and aspartate by Sreptococcus faecalis.

Uptake of arsenate and phosphate by Streptococcus faecalis 9790 is strictly dependent on concurrent energy metabolism and essentially unidirectional. targinine supports uptake only in presence of glycerol or related substances; glycerol is not directly involved in transport but depletes the cellular orthophosphate pool and thus relieves feedback inhibition of transport. Uptake of phosphate and arsenate is stimulated by K+ and by other permeant cations. The results suggest that electroneutrality is preserved by compensatory movement of either H+ or OH minus. Ionophores and N,N'-dicyclohexylcarbodiimide, which prevent establishment of a proton motive force, block the accumulation of thiomethylgalactoside and of threonine but not that of arsenate or phosphate. We conclude that arsenate accumulation requires adenosine 5'-triphosphate but is not driven by the proton-motive force. However, conditions and reagents that lower the cytoplasmic pH do inhibit accumulation of arsenate and phosphate, suggesting that uptake depends on the capacity of the cells to maintain a neutral or alkaline cytoplasm. We therefore propose that phosphate accumulation is an electroneutral exchange for OH driven by adenosine 5'-triphosphate or by a metabolite thereof. Accumulation of aspartate and glutamate also requires adenosine 5'-triphosphate but not the proton-motive force and may involve a similar mechanism.     

Adenosine is inherently favored as the branch-site RNA nucleotide in a structural context that resembles natural RNA splicing

We previously used in vitro selection to identify the 7S11 deoxyribozyme, which catalyzes formation of 2',5'-branched RNA using a branch-site adenosine nucleophile and a 5'-triphosphate electrophile. An unanswered question is whether the use of branch-site adenosine is inherently preferred or a chance event during the particular selection experiment. Here we have found that deoxyribozymes newly selected to use uridine as the branch-site RNA nucleotide in a structural context that resembles natural RNA splicing instead prefer a branch-site adenosine, although adenosine was never available during the selection itself. Our results support a chemical basis for nature's choice of the branch-site nucleotide, which is almost always adenosine in group II introns and the spliceosome.     

Methyl-coenzyme M, an intermediate in methanogenic dissimilation of C1 compounds by Methanosarcina barkeri.

Extracts of Methanosarcina barkeri possess a specific methyltransferase that catalyzes the transfer of the methyl group of methanol to 2-mercaptoethanesulfonic acid. Over a fourfold range in added 2-mercaptoethanesulfonic acid, the formation of 2-(methylthio)ethanesulfonic acid exhibited a 1:1 ratio to 2-mercaptoethanesulfonic acid added. This reaction required adenosine 5'-triphosphate; a maximal ratio (mole/mole) of 85 methyl groups was transferred per adenosine 5'-triphosphate added. The methyltransferase was found in extracts of methanol-grown cells as well as in extracts of hydrogen-grown cells. In extracts of cells grown on either substrate, 2-(methylthio)ethanesulfonic acid was formed from added methanol or methylamine but not from acetate.