Multiple forms of Pseudomonas multivorans glucose-6-phosphate and 6-phosphogluconate dehydrogenases: differences in size, pyridine nucleotide specificity, and susceptibility to inhibition by adenosine 5'-triphosphate

Pseudomonas cepacia mutants blocked in the Entner-Doudoroff pathway

Pseudomonas cepacia mutants deficient in either 6-phosphogluconate (6PGA) dehydratase (Edd-) or 2-keto-3-deoxy-6-phosphogluconate (KDPG) aldolase (Eda-) failed to utilize glucose or gluconate despite the prominence of of 6-phosphogluconate dehydrogenase (6PGAD) ii this bacterium and the potential for utilizing the pentose shunt suggested by its growth on ribitol and xylose. The Eda- strains grew normally on glucuronic acid, indicating that in P. cepacia its degradation does not depend upon KDPG aldolase as it does in Escherichia coli. Both 6PGA dehydratase and KDPG aldolase were inducible enzymes, with 6PGA rather than gluconate the apparent inducer. Edd- as well as Eda- strains were sensitive to growth inhibition by glucose, gluconate, fructose, and related carbohydrates when these substrates were present in combination with alternate carbon sources such as citrate or phthalate, presumably as a consequence of accumulation and toxicity of 6PGA, KDPG, or both. Edd- mutants were somewhat less sensitive to such inhibition than were Eda- strains. Certain derivatives of the Edd- strains we examined were able to utilize gluconate despite their deficiency of 6PGA dehydratase. Such mutants formed higher levels of 6PGAD than did the wild type. It is likely that the elevated levels of 6PGAD in these strains prevents accumulation of toxic levels of 6PGA that would otherwise result from a block in he Entner-Doudoroff pathway. The results suggest that P. cepacia can mutate to grow slowly on gluconate utilizing only the pentose shunt.

Purification and properties of glucose-6-phosphate dehydrogenase (NADP+/NAD+) and 6-phosphogluconate dehydrogenase (NADP+/NAD+) from methanol-grown Pseudomonas C

Glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate:NADPH+ 1-oxidoreductase, EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate:NADP+ 2-oxidoreductase, EC 1.1.1943) have been purified from methanol-grown Pseudomonas C. Glucose-6-phosphate dehydrogenase exhibits activity with either NADP+ or NAD+ as coenzymes, V NADP+ = 0.96 V NAD+.Km values of 22, 290, and 250 microns are obtained for NADP+, NAD+ and glucose 6-phosphate (NADP+ as the coenzyme), respectively. ATP inhibits Glc-6P dehydrogenase activity with NAD+ as coenzyme and to a less extent the activity with DANP+. In the presence of MgCl2, ATP inhibition of Blc-6P dehydrogeanse activity is abolished. 6-Phosphogluconate dehydrogenase has a dual specificity for both NADP+ or NAD+ as coenzymes, V NADP+ = 1.66 V NAD+.Km values of 20, 500 and 100 microns are obtained for NADP+, NAD+ and 6-phosphogluconate (NADP+ as the coenzyme), respectively. With NAD+ as the coenzyme ATP inhibits 6-phosphogluconate dehydrogeanse activity, while with NADP+ as the coenzyme, activity was less affected. The possible role of these enzymes in the metabolism of one-carbon (C1)-compounds in Pseudomonas C is discussed and compared with other methylotrophic microorganisms.

Response of Pseudomonas cepacia to beta-Lactam antibiotics: utilization of penicillin G as the carbon source

Pseudomonas cepacia utilized penicillin G as the sole source of carbon and energy. We report here an unexplained correlation between lysine auxotrophy and beta-lactamase deficiency, resulting in loss of capacity to utilize penicillin.

Pseudomonas cepacia mutants blocked in the direct oxidative pathway of glucose degradation

Glucose dehydrogenase-deficient strains of Pseudomonas cepacia grew normally with glucose as carbon source, indicating that the direct pathway of glucose oxidation does not play an essential role in this bacterium.

Branched chain amino acid aminotransferase isoenzymes of Pseudomonas cepacia

Pseudomonas cepacia grew rapidly using a mixture of all three branched chain amino acids as carbon source, but failed to use individual branched chain amino acids as sole carbon source. Extracts of bacteria grown on branched chain amino acids had between 2- and 3-fold higher levels of alpha-ketoglutarate-dependent branched chain amino acid aminotransferase activity than extracts of glucose-grown bacteria. The increase in enzyme activity was due to the presence of a second aminotransferase not detected in extracts of glucose-grown bacteria. The enzyme, which presumably plays a role in branched chain amino acid degradation, had an apparent molecular weight (mol.wt.) of 75,000. The other aminotransferase was formed constitutively and apparently functions in synthesis of branched chain amino acids. It was more stable than the 75,000 mol.wt. enzyme, and was purified to homogeneity and found to be a 180,000 mol.wt. oligomer containing 6 subunits of approximately 30,000 mol.wt. Antiserum prepared against the purified enzyme inhibited its activity but failed to influence the activity of the 75,000 mol.wt. aminotransferase, suggesting that the two isoenzymes are encoded by different genes.

Purification and properties of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase from a methanol-utilizing yeast, Candida boidinii

Glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP oxidoreductase, EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate: NADP oxidoreductase, EC 1.1.1.44) were purified approx. 1700 fold and 330 fold, respectively, from Candida boidinii grown on methanol. The final enzyme preparations were homogeneous as judged by polyacrylamide gel electrophoresis. The molecular weights of the enzymes were estimated to be 118 000 and 110 000, respectively. Both enzymes are composed of two probably identical subunits and the molecular weights of the polypeptide chains were calculated to be 61 000 and 58 000, respectively. From a consideration of enzyme activities and types of inhibition by different metabolites the role of these two enzymes in glucose- and methanol-metabolism is discussed.

Mannitol and fructose catabolic pathways of Pseudomonas aeruginosa carbohydrate-negative mutants and pleiotropic effects of certain enzyme deficiencies

Mutant strains of Pseudomonas aeruginosa PAO were isolated on the basis of their inability to utilize mannitol as sole carbon source for growth. Four linkage groups (I through IV) among these mutant strains were resolved by two-factor crosses using the general transducing phage F116, and the strains appeared to contain point mutations as evidenced by ability to give rise to spontaneous revertants with wild phenotype on mannitol minimal agar. Group I strains were affected only in ability to grow on mannitol; all were deficient in inducible mannitol dehydrogenase activity, and all but one were deficient in inducible mannitol transport activity. Fructokinase was induced in group I strains and in wild-type bacteria during growth in the presence of mannitol but not fructose, indicating the presence of a pathway specific for endogenously generated fructose. Cells grown on fructose contained phosphoenolpyruvate:fructose-1-phosphotransferase activity, and mannitol-grown cells contained a lower level of this activity. Group II mutants were deficient in constitutive phosphoglucoisomerase, failed to grow on mannitol, grew very slowly on glycerol and fructose, but grew normally on glucose and gluconate. Group III strains were deficient in both nicotinamide adenine dinucleotide- and nicotinamide adenine dinucleotide phosphate-linked glucose-6-phosphate dehydrogenase activities that reside in a single enzyme species. 6-Phosphogluconate appeared to be the inductive effector for this enzyme, which was not required for aerobic growth on glucose or gluconate. A single mannitol-negative mutant in group IV also failed to grow on glycerol and glucose, but no biochemical lesion was identified.

Characterization of the fatty acid-sensitive glucose 6-phosphate dehydrogenase from Pseudomonas cepacia

The adenosone 5'-triphosphate-insensitive glucose 6-phosphate dehydrogenase from Pseudomonas cepacia has been found to be strongly inhibited by long-chain fatty acids and their acyl coenzyme A esters, suggesting that an important role of this isoenzyme might be to provide reduced nicotinamide adenine dinucleotide phosphate for reductive steps in fatty acid synthesis. The enzyme, which has been redesignated the fatty acid-sensitive glucose 6-phosphate dehydrogenase, has been purified to homogeneity using affinity chromatography with nicotinamide adenine dinulceotide phosphate-substituted Sepharose as a key step in the purification. The purified preparations were used to study the immunological properties and subunit composition of the enzyme and its relationship to the adenosine 5'-triphosphate-sensitive glucose 6-phosphate dehydrogenase present in extracts of P. cepacia. Although both enzymes were found to be composed of similar size subunits of about 60,000 daltons, immunological studies failed to demonstrate any antigenic similarity between them. Studies of the sedimentation behavior of the fatty acid-sensitive enzyme in sucrose gradients indicated that its apparent molecular weight is increased in the presence of glucose 6-phosphate and suggest that it may exist in an aggregated state in vivo. Palmitoyl coenzyme A, which strongly inhibited the enzyme, failed to influence its sedimentation behavior.

Cyclic adenosine 3',5'-monophosphate levels and activities of adenylate cyclase and cyclic adenosine 3',5'-monophosphate phosphodiesterase in Pseudomonas and Bacteroides

A modified Gilman assay was used to determine the concentrations of cyclic adenosine 3',5'-monophosphate (cAMP) in rapidly filtered cells and in the culture filtrates of Pseudomonas aeruginosa, Escherichia coli K-12, and Bacteroides fragilis. In P. aeruginosa cultures, levels of cAMP in the filtrate increased with the culture absorbance (3.5 to 19.8 X 10(-9) M) but did not vary significantly with the carbon source used to support growth. Intracellular concentrations (0.8 to 3.2 X 10(-5) M) were substantially higher and did not vary appreciably during growth or with carbon source. Sodium cAMP (5 mM) failed to reverse the catabolite repression of inducible glucose-6-phosphate dehydrogenase (EC 1.1.1.49) synthesis caused by the addition of 10 mM succinate. Exogenous cAMP also had no discernible effect on the catabolite repression control of inducible mannitol dehydrogenase (EC 1.1.1.67). P. aeruginosa was found to contain both soluble cAMP phosphodiesterase (EC 3.1.4.17) and membrane-associated adenylate cyclase (EC 4.6.1.1) activity, and these were compared to the activities detected in crude extracts of E. coli. B. fragilis crude cell extracts contain neither of these enzyme activities, and little or no cAMP was detected in cells or culture filtrates of this anaerobic bacterium.

D-glucose-6-phosphate dehydrogenase (Entner-Doudoroff enzyme) from Pseudomonas fluorescens. Purification, properties and regulation

1. The existence of two different D-glucose-6-phosphate dehydrogenases in Pseudomonas fluorescens has been demonstrated. Based on their different specificity and their different metabolic regulation one enzyme is appointed to the Entner-Doudoroff pathway and the other to the hexose monophosphate pathway. 2. A procedure is described for the isolation of that D-glucose-6-phosphate dehydrogenase which forms part of the Entner-Doudoroff pathway (Entner-Doudoroff enzyme). A 950-fold purification was achieved with an overall yield of 44%. The final preparation, having a specific activity of about 300 mumol NADH formed per min per mg protein, was shown to be homogeneous. 3. The molecular weight of the Entner-Doudoroff enzyme has been determined to be 220000 by gel permeation chromatography, and that of the other enzyme (Zwischenferment) has been shown to be 265000. 4. The pI of the Entner-Doudoroff enzyme has been shown to be 5.24 and that of the Zwischenferment 4.27. The Entner-Doudoroff enzyme is stable in the range of pH 6 to 10.5 and shows its maximal activity at pH 8.9. 5. The Entner-Doudoroff enzyme showed specificity for NAD+ as well as for NADP+ and exhibited homotropic effects for D-glucose 6-phosphate. It is inhibited by ATP which acts as a negative allosteric effector. Other nucleoside triphosphates as well as ADP are also inhibitory. 6. The enzyme catalyzes the transfer of the axial hydrogen at carbon-1 of beta-D-glucopyranose 6-phosphate to the si face of carbon-4 of the nicotinamide ring and must be classified as B-side stereospecific dehydrogenase.

Purification and characterization of the two 6-phosphogluconate dehydrogenase species from Pseudomonas multivorans

The two species of 6-phosphogluconate dehydrogenase (EC 1.1.1.43) from Pseudomonas multivorans were resolved from extracts of gluconate-grown bacteria and purified to homogeneity. Each enzyme comprised between 0.1 and 0.2% of the total cellular protein. Separation of the two enzymes, one which is specific for nicotinamide adenine dinucleotide phosphate and the other which is active with nicotinamide adenine dinucleotide or nicotinamide adenine dinucleotide phosphate was facilitated by the marked difference in their respective isoelectric points, which were at pH 5.0 and 6.9. Comparison of the subunit compositions of the two enzymes indicated that they do not share common peptide chains. The enzyme active with nicotinamide adenine dinucleotide was composed of two subunits of about 40,000 molecular weight, and the nicotinamide adenine dinucleotide phosphate-specific enzyme was composed of two subunits of about 60,000 molecular weight. Immunological studies indicated that the two enzymes do not share common antigenic determinants. Reduced nicotinamide adenine dinucleotide phosphate strongly inhibited the 6-phosphogluconate dehydrogenase active with nicotinamide adenine dinucleotide by decreasing its affinity for 6-phosphogluconate. Guanosine-5'-triphosphate had a similar influence on the nicotinamide adenine dinucleotide phosphate-specific 6-phosphogluconate dehydrogenase. These results in conjunction with other data indicating that reduced nicotinamide adenine dinucleotide phosphate stimulates the conversion of 6-phosphogluconate to pyruvate by crude bacterial extracts suggest that in P. multivorans, the relative distribution of 6-phosphogluconate into the pentose phosphate and Entner-Doudoroff pathways might be determined by the intracellular concentrations of reduced nicotinamide adenine dinucleotide phosphate and purine nucleotides.

Purification and characterization of the Pseudomonas multivorans glucose-6-phosphate dehydrogenase active with nicotinamide adenine dinucleotide

The Pseudomonas multivorans glucose-6-phosphate dehydrogenase (EC 1.1.1.49) active with nicotinamide adenine dinucleotide, which is inhibitable by adenosine-5'-triphosphate, was purified approximately 1,000-fold from extracts of glucose-grown bacteria, and characterized with respect to subunit composition, response to different inhibitory ligands, and certain other properties. The enzyme was found to be an oligomer composed of four subunits of about 60,000 molecular weight. Reduced nicotinamide adenine dinucleotide phosphate, but not reduced nicotinamide adenine dinucleotide, was found to be a potent inhibitor of its activity. The range of concentrations of reduced nicotinamide adenine dinucleotide phosphate over which inhibition occurred was about 100-fold lower than that for adenosine-5'-triphosphate. The data suggest that reduced nicotinamide adenine dinucleotide phosphate may play an important role in regulation of hexose phosphate metabolism in P. multivorans. Antisera prepared against the purified enzyme strongly inhibited its activity, but failed to inhibit the activity of the nicotinamide adenine dinucleotide phosphate-specific glucose-6-phosphate dehydrogenase which is also present in extracts of this bacterium. Immunodiffusion experiments confirmed the results of the enzyme inhibition studies, and failed to support the idea that the two glucose-6-phosphate dehydrogenase species from P. multivorans represent different oligomeric forms of the same protein.

Glucolysis in Pseudomonas putida: physiological role of alternative routes from the analysis of defective mutants

A number of mutants in which glucolysis is impaired have been isolated from Pseudomonas putida. The study of their behavior shows that this organism possesses a single glucolytic pathway with physiological significance. The first step of the pathway consists in the oxidation of glucose into gluconate. Two proteins with glucose dehydrogenase activity appear to exist in P. putida but the reasons for this duplicity are not clear. The process continues with the formation of 2-ketogluconate which is in turn converted into gluconate-6-phosphate. This is proved by the fact that mutants unable to form gluconate-6-phosphate from 2-ketogluconate show extremely slow growth on glucose or gluconate (generation times are increased more than 100 times). Other possible routes for the conversion of glucose into gluconate-6-phosphate, the glucose-6-phosphate pathway, or the direct phosphorylation of the gluconate formed by glucose oxidation are only minor shunts in P. putida. The Entner-Doudoroff enzymes, which catalyze the conversion of gluconate-6-phosphate into pyruvate and triosephosphate, appear to be essential to grow on glucose and also on gluconate and 2-ketogluconate. A significative role of the pentose route in the catabolism of these substrates is not apparent from this study. In contrast, P. putida strains showing no activity of the Entner-Doudoroff enzymes grow readily on fructose, although there is evidence that this hexose is at least partially catabolized via gluconate-6-phosphate.