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PubMed1972

Isolation, identification, and characterization of a lipoate-degrading pseudomonad and of a lipoate catabolite.

A strain of bacteria that can degrade lipoic acid was isolated from soil. The bacterium, adapted to use 0.4% dl-lipoate as the sole organic substrate to supply carbon, sulfur, and energy, was identified morphologically and physiologically as a strain of Pseudomonas putida. Degradation of 1,6-(14)C-lipoic acid, synthesized from 1,6-(14)C-adipic acid, was evidenced by: (i) loss of approximately 50% of the total radioactivity from the medium after bacterial growth; (ii) appearance of (14)C-degradation products upon paper and thin-layer chromatography of the culture medium; and (iii) oxygraphically measured utilization of O(2) by cells in the presence of lipoate or other oxidizable substrates. Analyses of the benzene extract of culture medium by infrared, nuclear magnetic resonance, and mass spectrometry, and by gas-liquid chromatography after desulfuration, have characterized bisnorlipoic acid, or 4,6-dithiohexanoic acid, as the major catabolite present in the medium. beta-Oxidation of the side chain is thus proven to be a pathway employed by the pseudomonad to degrade lipoic acid.

Acetates↗
PubMed1972

Mutant of Escherichia coli with derepressed levels of the biotin biosynthetic enzymes.

A cross-feeding technique was used to isolate a mutant of Escherichia coli K-12 that excretes 1,000 times more biotin into the growth medium than the parent strain. The mutant has high levels of the biotin biosynthetic enzymes even when grown in the presence of biotin. Desthiobiotin synthetase, the level of which was used as a measure of the biosynthetic activity of the biotin pathway, is not repressed by biotin at the concentration 250,000 times that sufficient to repress the enzyme in the wild type. The mutant gene is cotransducible with argC located at 77 min on the E. coli chromosome.

Acetates↗
PubMed1976

Lysine catabolism in Rhizoctonia leguminicola and related fungi.

The catabolism of lysine was studied in several yeasts and fungi. Results with cell-free extracts of Rhizoctonia leguminicola support a proposed pathway involving (D- and L-) EPSILON-N-acetyllysine, alpha-keto-epsilon-acetamidohexanoic acid, delta-acetamidovaleric acid, and delta-aminovaleric acid in the conversion of L-lysine to shortchain organic acids. Label from radioactive L-lysine was found to accumulate in D- and L-epsilon-N-acetyllysine, delta-acetamidovaleric acid, delta-aminovaleric acid, and glutaric acid in cultures of R. leguminicola, Neurospora crassa, Saccharomyces cerevisiae, and Hansenula saturnus, suggesting that the proposed omega-acetyl pathway of lysine catabolism is generalized among yeasts and fungi. In N. crassa, as is the case in R. leguminicola, the major precursor of L-pipecolic acid was the L-isomer of lysine; 15N experiments were consistent with delta1-piperideine-2-carboxylic acid as an intermediate in the transformation.

Caproates↗
PubMed1978

Chemoresponses of Chlamydomonas reinhardtii.

Cells of Chlamydomonas reinhardtii have been found to respond to chemicals in two ways: chemokinesis and chemotaxis. Several amino acids, fatty acids, and inorganic salts can stimulate these responses.

Amino Acids↗
PubMed1978

Role of the Escherichia coli aromatic amino acid aminotransferase in leucine biosynthesis.

Strains of Escherichia coli that lack the branched-chain amino acid amino-transferase because of mutations in the ilvE gene had no growth requirement for leucine when the cells contained the aromatic amino acid aminotransferase that is the product of the tyrB gene. The presence of leucine increased the generation time of these cells and decreased the specific activity of the aromatic amino acid aminotransferase. It is concluded that this enzyme functions efficiently in leucine biosynthesis and can be repressed by leucine as well as by tyrosine.

Caproates↗
PubMed1980

Enzymes involved in 3,5-diaminohexanoate degradation by Brevibacterium sp.

Cell-free extracts of Brevibacterium sp. L5 grown on DL-erythro-3,5-diaminohexanoate were found to contain a 3-keto-5-aminohexanoate cleavage enzyme that converts 3-keto-5-aminohexanoate and acetyl-coenzyme A (CokA) to 3-aminobutyryl-CoA and acetoacetate and a deaminase that coverts L-3-aminobutyryl-CoA to crotonyl-CoA. The cleavage enzyme has been purified extensively, and some of its properties have been determined for comparison with the 3-keto-6-acetamido-hexanoate cleavage enzyme of Pseudomonas sp. B4. The deaminase has been partially purified and characterized. Both the cleavage enzyme and the deaminase are induced by growth on 3,5-diaminohexanoate. The presence of these and other accessory enzymes in Brevibacterium sp. extracts accounts for the results of earlier tracer experiments which showed that C-1 and C-2 of 3-keto-5-aminohexanoate are converted mainly to acetoacetate and acetate, whereas C-3 to C-6 are converted mainly to 3-hydroxybutyrate or its coenzyme A thiolester. The enzymes observed in extracts of Brevibacterium sp. can account for the conversion of 3,5-diaminohexanoate to acetyl-CoA.

Amino Acids, Diamino↗
PubMed1981

Purification of a branched-chain keto acid dehydrogenase from Pseudomonas putida.

We purified branched-chain keto acid dehydrogenase to a specific activity of 10 mumol/min per mg of protein from Pseudomonas putida grown on valine. The purified enzyme was active with 2-ketoisovalerate, 2-ketoisocaproate, and 2-keto-3-methylvalerate in a ratio of 1.0:0.8:0.7 but showed no activity with either pyruvate or 2-ketoglutarate. There were four polypeptides in the purified enzyme (molecular weights, 49,000, 46,000, 39,000, and 37,000). The purified enzyme was deficient in the specific lipoamide dehydrogenase produced during growth on valine (molecular weight, 49,000). Branched-chain keto acid dehydrogenase required L-valine, oxidized nicotinamide adenine dinucleotide, coenzyme A, thiamine pyrophosphate, and magnesium chloride. A partially purified preparation catalyzed the oxidation of 2-keto-[1-14C]isovalerate to [14C]carbon dioxide, isobutyryl-coenzyme A, and reduced nicotinamide adenine dinucleotide in equimolar amounts. Both the Km and the Vmax for 2-ketoisovalerate were affected by the addition of L-valine to the assay mixture. However, only the Vmax values for oxidized nicotinamide adenine dinucleotide and coenzyme A were affected when L-valine was present. This suggested that valine acted by affecting the binding of branched-chain keto acids to subunit E1 of the complex.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1983

Bacterial formation and metabolism of 6-hydroxyhexanoate: evidence of a potential role for omega-oxidation.

Alkane-utilizing strains of Pseudomonas spp. were found to omega-oxidize hexanoate, 6-hydroxyhexanoate, and 6-oxohexanoate to adipic acid in 5, 30, and 90% molar yields, respectively, after induction with n-hexane. 6-Hydroxyhexanoate was identified as the immediate product of hexanoate omega-hydroxylation by whole cells and was further oxidized into adipic acid and an unexpected metabolite identified as 2-tetrahydrofuranacetic acid. This same metabolite, together with adipic acid, was also detected when similarly induced cells were incubated with hexanoate or 1,6-hexanediol, but not with 6-oxohexanoate (adipic semialdehyde). Cells grown on hexanoate and incubated with 6-hydroxyhexanoate were also found to accumulate 2-tetrahydrofuranacetic acid, which was not further degraded. Utilization of 6-hydroxyhexanoate for growth was restricted to those organisms also able to utilize adipate. Similar observations were made with 1,6-hexanediol serving as the carbon source and cells obtained from one organism, Pseudomonas aeruginosa PAO, grown either on 1,6-hexanediol or 6-hydroxyhexanoate, were found to be well induced for both 6-oxohexanoate and adipate oxidation. The results indicate that 6-hydroxyhexanoate and 1,6-hexanediol are susceptible to both beta- and omega-oxidative attack; however, the former pathway appears to be of no physiological significance since it generates 2-tetrahydrofuranacetic acid as a nonmetabolizable intermediate, making omega-oxidation via adipate the exclusive pathway for degradation.

Caproates↗
PubMed1987

Metabolism of gallate and phloroglucinol in Eubacterium oxidoreducens via 3-hydroxy-5-oxohexanoate.

The pathway for the anaerobic catabolism of gallic acid by Eubacterium oxidoreducans was studied by using both in vivo and cell-free systems. Cells grown with gallate and crotonate, but with no formate or H2, excreted pyrogallol and phloroglucinol into the medium. Gallate was decarboxylated by crude cell extracts, with pyrogallol as the only detectable product. Whole cells converted pyrogallol to phloroglucinol. A phloroglucinol reductase catalyzed the conversion of phloroglucinol to dihydrophloroglucinol when NADPH was used as the source of electrons. Both formate dehydrogenase (EC 1.2.1.43) and hydrogenase (EC 1.18.99.1) were present in cell extracts of gallate-formate-grown cells. These two enzymes were both NADP linked. Since either H2 or formate is required for cell growth with gallate or phloroglucinol, these results suggest that the oxidation of the reduced substrate may be indirectly linked to the reduction of phloroglucinol. A dihydrophloroglucinol hydrolase was present, which hydrolyzed dihydrophloroglucinol to 3-hydroxy-5-oxohexanoate. This six-carbon ring cleavage product then presumably can be broken down by a series of reactions similar to beta-oxidation. These reactions cleaved the six-carbon acid to 3-hydroxybutyryl-coenzyme A yielding acetate and butyrate as end products. A number of key enzymes involved in beta-oxidation and substrate-level phosphorylation were demonstrated in cell extracts.

Caproates↗
PubMed1993

Alpha-keto acids are novel siderophores in the genera Proteus, Providencia, and Morganella and are produced by amino acid deaminases.

Growth promotion and iron transport studies revealed that certain alpha-keto acids generated by amino acid deaminases, by enterobacteria of the Proteus-Providencia-Morganella group (of the tribe Proteeae), show significant siderophore activity. Their iron-binding properties were confirmed by the chrome azurol S assay and UV spectra. These compounds form ligand-to-metal charge transfer bands in the range of 400 to 500 nm. Additional absorption bands of the enolized ligands at 500 to 700 nm are responsible for color formation. Siderophore activity was most pronounced with alpha-keto acids possessing an aromatic or heteroaromatic side chain, like phenylpyruvic acid and indolylpyruvic acid, resulting from deamination of phenylalanine and tryptophan, respectively. In addition, alpha-keto acids possessing longer nonpolar side chains, like alpha-ketoisocaproic acid or alpha-ketoisovaleric acid and even alpha-ketoadipic acid, also showed siderophore activity which was absent or negligible with smaller alpha-keto acids or those possessing polar functional groups, like pyruvic acid, alpha-ketobutyric acid, or alpha-ketoglutaric acid. The fact that deaminase-negative enterobacteria, like Escherichia coli and Salmonella spp., could not utilize alpha-keto acids supports the view that specific iron-carboxylate transport systems have evolved in members of the tribe Proteeae and are designed to recognize ferric complexes of both alpha-hydroxy acids and alpha-keto acids, of which the latter can easily be generated by L-amino acid deaminases in an amino acid-rich medium. Exogenous siderophores, like ferric hydroxamates (ferrichromes) and ferric polycarboxylates (rhizoferrin and citrate), were also utilized by members of the tribe Proteeae.

Amino Acids↗
PubMed2003

Conversion of Lactobacillus pentosus D-lactate dehydrogenase to a D-hydroxyisocaproate dehydrogenase through a single amino acid replacement.

The single amino acid replacement of Tyr52 with Leu drastically increased the activity of Lactobacillus pentosus NAD-dependent D-lactate dehydrogenase toward larger aliphatic or aromatic 2-ketoacid substrates by 3 or 4 orders of magnitude and decreased the activity toward pyruvate by about 30-fold, converting the enzyme into a highly active D-2-hydroxyisocaproate dehydrogenase.

Alcohol Oxidoreductases↗
PubMed2005

Gene cloning and molecular characterization of an extracellular poly(L-lactic acid) depolymerase from Amycolatopsis sp. strain K104-1.

We have isolated a polylactide or poly(L-lactic acid) (PLA)-degrading bacterium, Amycolatopsis sp. strain K104-1, and purified PLA depolymerase (PLD) from the culture fluid of the bacterium. Here, we cloned and expressed the pld gene encoding PLD in Streptomyces lividans 1326 and characterized a recombinant PLD (rPLD) preparation. We also describe the processing mechanism from nascent PLD to mature PLD. The pld gene encodes PLD as a 24,225-Da polypeptide consisting of 238 amino acids. Biochemical and Western immunoblot analyses of PLD and its precursors revealed that PLD is synthesized as a precursor (prepro-type), requiring proteolytic cleavage of the N-terminal 35-amino-acid extension including the 26-amino-acid signal sequence and 9-residue prosequence to generate the mature enzyme of 20,904 Da. The cleavage of the prosequence was found to be autocatalytic. PLD showed about 45% similarity to many eukaryotic serine proteases. In addition, three amino acid residues, H57, D102, and S195 (chymotrypsin numbering), which are implicated in forming the catalytic triad necessary for cleavage of amide bond of substrates in eukaryotic serine proteases, were conserved in PLD as residues H74, D111, and S197. The G193 residue (chymotrypsin numbering), which is implicated in forming an oxyanion hole with residue S195 and forms an important hydrogen bond for interaction with the carbonyl group of the scissile peptide bond, was also conserved in PLD. The functional analysis of the PLD mutants H74A, D111A, and S197A revealed that residues H74, D111, and S197 are important for the depolymerase and caseinolytic activities of PLD and for cleavage of the prosequence from pro-type PLD to form the mature one. The PLD preparation had elastase activity which was not inhibited by 1 mM elastatinal, which is 10 times higher than needed for complete inhibition of porcine pancreatic elastase. The rPLD preparation degraded PLA with an average molecular mass of 220 kDa into lactic acid dimers through lactic acid oligomers and finally into lactic acid. The PLD preparation bound to high polymers of 3-hydoxybutyrate, epsilon-caprolacton, and butylene succinate as well as PLA, but it degraded only PLA.

3-Hydroxybutyric Acid↗
PubMed1967

Function of the glyoxylate-condensing enzymes. I. Growth of Escherichia coli on n-valeric acid.

Growth of Escherichia coli E-26 on valeric acid results in the formation of a mutant population characterized by the ability to form constitutively several glyoxylate-condensing enzymes. This mutant also differs from the parent organism in the ability to effect rapid growth on a series of short-chain fatty acids. These mutants were utilized in postulating genetic relationships among the various glyoxylate-condensing activities and also in correlating the presence of these enzymes with the ability of the mutants to initiate growth quickly on short-chain fatty acids.

Acetates↗
PubMed1968

Anti-Pasteurella pestis factor. 3. Effects of fatty acids on Pasteurella pestis.

The bactericidal activity and the chemical and physical characteristics of lipid fractions of extracts from organs of normal mice and guinea pigs have been described previously. The present study describes the effects of commercially prepared fatty acids which are representative of those found in the extracts. Saturated fatty acids with 12, 14, and 16 carbon atoms and unsaturated fatty acids with more than one double bond were the most effective in killing Pasteurella pestis. Tweens 20 and 80, Spans 40 and 80, and some of the methyl esters of the fatty acids did not strongly inhibit P. pestis. It was concluded, therefore, that both the length of the carbon chain and the presence of the carboxyl group of the free fatty acids were important in their effects on P. pestis. Neither the very active lauric acid nor the relatively inactive oleic acid appeared to severely alter the morphology of P. pestis. Supernatant fluids from incubated mixtures of sodium laurate or sodium oleate and cells did not contain significantly greater concentrations of proteins or nucleic acids than did the controls. These observations do not preclude an alteration of the permeability of the cell walls.

Caproates↗
PubMed1969

Fidelity of initiation of protein synthesis after premature chain termination in polarity mutants.

beta-Isopropylmalate dehydrogenase, the product of the second cistron of the leucine operon in Salmonella typhimurium, produced by strains bearing nonsense or frameshift mutations in the first cistron of the operon was shown to be homogeneous as judged by electrophoretic and immunological techniques. Amino terminal analyses suggest that the enzyme produced by the mutant strains is identical with the wild-type enzyme. This view is supported by the observation that a nonsense mutant strain beta-isopropylmalate dehydrogenase copurifies with the wild-type enzyme. The results suggest that the uncoupling of normal chain termination and reinitiation does not interfere with the fidelity of subsequent polypeptide chain initiation in a polycistronic messenger ribonucleic acid.

Alcohol Oxidoreductases↗