Biomedical subjects

H J Knackmuss

Publications and source records attributed to H J Knackmuss.

At least 37 records · Page 2Linked to original sources

PubMed1994

Aerobic biodegradation of 3-aminobenzoate by gram-negative bacteria involves intermediate formation of 5-aminosalicylate as ring-cleavage substrate.

The aerobic metabolism of 3-aminobenzoate by bacteria was studied. Bacterial strains degrading 3-aminobenzoate were obtained by enrichment with 3-aminobenzoate (strain Ia3) or 5-aminosalicylate (strains BN9 and 5AS1). During growth with 3-aminobenzoate, strain Ia3 and strain 5AS1 transiently accumulated 5-aminosalicylate in the culture broth. In the presence of inhibitors of 5-aminosalicylate 1,2-dioxygenase, resting cells of all three strains converted 3-aminobenzoate to stoichiometric amounts of 5-aminosalicylate. 5-Aminosalicylate 1,2-dioxygenase activity was induced in all strains after growth with 3-aminobenzoate or 5-aminosalicylate, but not after growth in complex media.

Aminobenzoates↗

PubMed1994

Enantioselective hydrolysis of racemic naproxen nitrile and naproxen amide to S-naproxen by new bacterial isolates.

Bacteria were enriched from soil samples with succinate as a carbon source and racemic naproxen nitrile [2-(6-methoxy-2-naphthyl)propionitrile] as sole source of nitrogen. Since naproxen nitrile was only poorly soluble in water media amended with different water-immiscible organic phases were used for the enrichments. With pristane (2,6,10,14-tetramethylpentadecane) as the organic phase two bacterial strains were isolated (strain C3II and strain MP50) which were identified as rhodococci. Cells of both strains converted naproxen nitrile via naproxen amide to naproxen. From racemic naproxen nitrile Rhodococcus sp. C3II formed S-naproxen amide and subsequently S-naproxen. Racemic naproxen amide was hydrolysed to S-naproxen. Rhodococcus sp. MP50 converted racemic naproxen nitrile predominantly to R-naproxen amide and racemic naproxen amide to S-naproxen. With both strains racemic naproxen amide was converted to S-naproxen with an enantiomeric excess > 99% at a conversion rate up to 80% of the theoretical value. In strain C3II the enzymes which hydrolysed naproxen nitrile and naproxen amide were present only at a low constitutive level. In contrast, in Rhodococcus sp. MP50 these activities were induced when grown in the presence of various nitriles.

Amides↗

PubMed1994

Inability of muconate cycloisomerases to cause dehalogenation during conversion of 2-chloro-cis,cis-muconate.

The conversion of 2-chloro-cis,cis-muconate by muconate cycloisomerase from Pseudomonas putida PRS2000 yielded two products which by nuclear magnetic resonance spectroscopy were identified as 2-chloro- and 5-chloromuconolactone. High-pressure liquid chromatography analyses showed the same compounds to be formed also by muconate cycloisomerases from Acinetobacter calcoaceticus ADP1 and Pseudomonas sp. strain B13. During 2-chloro-cis,cis-muconate turnover by the enzyme from P. putida, 2-chloromuconolactone initially was the major product. After prolonged incubation, however, 5-chloromuconolactone dominated in the resulting equilibrium. In contrast to previous assumptions, both chloromuconolactones were found to be stable at physiological pH. Since the chloromuconate cycloisomerases of Pseudomonas sp. strain B13 and Alcaligenes eutrophus JMP134 have been shown previously to produce the trans-dienelactone (trans-4-carboxymethylene-but-2-en-4-olide) from 2-chloro-cis,cis-muconate, they must have evolved the capability to cleave the carbon-chlorine bond during their divergence from normal muconate cycloisomerases.

4-Butyrolactone↗

PubMed1994

Degradation of fluorene by Brevibacterium sp. strain DPO 1361: a novel C-C bond cleavage mechanism via 1,10-dihydro-1,10-dihydroxyfluoren-9-one.

Angular dioxygenation has been established as the crucial step in dibenzofuran degradation by Brevibacterium sp. strain DPO 1361 (V. Strubel, K. H. Engesser, P. Fischer, and H.-J. Knackmuss, J. Bacteriol. 173:1932-1937, 1991). The same strain utilizes biphenyl and fluorene as sole sources of carbon and energy. The fluorene degradation sequence is proposed to be initiated by oxidation of the fluorene methylene group to 9-fluorenol. Cells grown on fluorene exhibit pronounced 9-fluorenol dehydrogenase activity. Angular dioxygenation of the 9-fluorenone thus formed yields 1,10-dihydro-1,10-dihydroxyfluoren-9-one (DDF). A mechanistic model is presented for the subsequent C-C bond cleavage by an NAD(+)-dependent DDF dehydrogenase, acting on the angular dihydrodiol. This enzyme was purified and characterized as a tetramer of four identical 40-kDa subunits. The following Km values were determined: 13 microM for DDF and 65 microM for 2,3-dihydro-2,3-dihydroxybiphenyl. The enzyme also catalyzes the production of 3-(2'-carboxyphenyl)catechol, which was isolated, and structurally characterized, in the form of the corresponding lactone, 4-hydroxydibenzo-(b,d)-pyran-6-one. Stoichiometry analysis unequivocally demonstrates that angular dioxygenation constitutes the principal pathway in Brevibacterium sp. strain DPO 1361.

Alcohol Oxidoreductases↗

PubMed1994

Identification of a hydride-Meisenheimer complex as a metabolite of 2,4,6-trinitrotoluene by a Mycobacterium strain.

A bacterial strain, Mycobacterium sp. strain HL 4-NT-1, enriched with 4-nitrotoluene as its sole source of nitrogen, was able to metabolize 2,4,6-trinitrotoluene under aerobic conditions. The dark red-brown metabolite, which accumulated in the culture fluid, was identified as a hydride-Meisenheimer complex by comparison with an authentic synthetic sample.

Biotransformation↗

PubMed1993

Purification and properties of 2'-hydroxybenzalpyruvate aldolase from a bacterium that degrades naphthalenesulfonates.

2'-Hydroxybenzalpyruvate aldolase catalyzes the cleavage of 2'-hydroxybenzalpyruvate to salicylaldehyde and pyruvate. This reaction is part of the degradative pathways for naphthalene and naphthalenesulfonates by bacteria. 2'-Hydroxybenzalpyruvate aldolase has been purified to homogeneity from a bacterium that degrades naphthalenesulfonates (strain BN6). The enzyme has a molecular weight of about 120,000 and is composed of identical subunits with a molecular weight of about 38,500. Thus the enzyme appears to exist as a trimeric oligomer. The NH2-terminal amino acid sequence did not show significant homology to other published amino acid sequences. Extensive loss of enzyme activity occurred when the enzyme was incubated with 2'-hydroxybenzalpyruvate in the presence of sodium borhydride. This suggested the intermediate formation of a stable Schiff base between enzyme and substrate. 2'-Hydroxybenzalpyruvate aldolase was inhibited by p-chloromercuribenzoate and by the reaction product salicylaldehyde. The enzyme converted 2'-hydroxybenzalpyruvate, 2',4'- and 2',6'-dihydroxybenzalpyruvate.

Aldehyde-Lyases↗

PubMed1993

Degradation of 2,4-dihydroxybenzoate by Pseudomonas sp. BN9.

The aerobic degradation of 2,4-dihydroxybenzoate by Pseudomonas sp. BN9 was studied. Intact cells of Pseudomonas sp. BN9 grown with 2,4-dihydroxybenzoate oxidized 2,4-dihydroxybenzoate but not salicylate. Cell-free extracts of Pseudomonas sp. BN9 converted 2,4-dihydroxybenzoate after the addition of NAD(P)H. A partially purified protein fraction converted 2,4-dihydroxybenzoate with NADH to 1,2,4-trihydroxybenzene. 1,2,4-Trihydroxybenzene was converted by a 1,2-dioxygenase to maleylpyruvate, which was reduced by a NADH-dependent enzyme to 3-oxoadipate. 2,4-Dihydroxybenzoate 1-monooxygenase, 1,2,4-trihydroxybenzene 1,2-dioxygenase and maleylpyruvate reductase were induced in Pseudomonas sp. BN9 after growth with 2,4-dihydroxybenzoate.

Aerobiosis↗

PubMed1993

Metabolism of 2-chloro-4-methylphenoxyacetate by Alcaligenes eutrophus JMP 134.

2-Chloro-4-methylphenoxyacetate is not a growth substrate for Alcaligenes eutrophus JMP 134 and JMP 134-1. It is, however, being transformed by enzymes of 2,4-dichlorophenoxyacetic acid metabolism to 2-chloro-4-methyl-cis,cis-muconate, which is converted by enzymatic 1,4-cycloisomerization to 4-carboxymethyl-2-chloro-4-methylmuconolactone as a dead end metabolite. Chemically, only 3,6-cycloisomerization occurs, giving rise to both diastereomers of 4-carboxychloromethyl-3-methylbut-2-en-4-olide. Those lactones harboring a chlorosubstituent on the 4-carboxymethyl side chain were surprisingly stable under physiological as well as acidic conditions.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1993

Syntrophic interactions during degradation of 4-aminobenzenesulfonic acid by a two species bacterial culture.

During synthrophic growth of Hydrogenophaga palleronii (strain S1) and Agrobacterium radiobacter (strain S2) with 4-aminobenzene sulfonate (4ABS) only strain S1 desaminates 4ABS by regioselective 3,4-dioxygenation. The major part of the metabolite catechol-4-sulfonate (4CS) is excreted and further metabolized by strain S2. Although both organisms harbour activities of protocatechuate pathways assimilation of the structural analog 4CS requires first of all enzyme activities with broader substrate specificity: protocatechuate 3,4-dioxygenase and carboxymuconate cycloisomerase activities were identified which in addition to the natural substrates also convert 4CS and 3-sulfomuconate respectively. 4-Carboxymethyl-4-sulfobut-2-en-4-olide (4SL) was identified as a metabolite. Its further metabolism requires a desulfonating enzyme which eliminates sulfite from (4SL) and generates maleylacetate. Convergence with the 3-oxoadipate pathway is catalyzed by a maleyl acetate reductase, which was identified in cell-free extracts of both organisms S1 and S2. Characteristically, only strain S1 can oxidize sulfite and thus contributes to the interdependence of the two bacteria during growth with 4ABS.

Biodegradation, Environmental↗

PubMed1993

Bacterial metabolism of 5-aminosalicylic acid: enzymic conversion to L-malate, pyruvate and ammonia.

5-Aminosalicylate (5AS) was converted to L-malate, pyruvate and ammonia by cell-free extracts from Pseudomonas sp. BN9 in the presence of glutathione. In the absence of glutathione, 5AS was oxidized to the ring-fission product cis-4-amino-6-carboxy-2-oxo-hexa-3,5-dienoate (cis-ACOHDA). Glutathione catalysed the spontaneous isomerization of cis-ACOHDA to its trans-isomer. The same reaction was catalysed by light and by acidic conditions. trans-ACOHDA was enzymically deaminated to fumarylpyruvate (trans-2,4-dioxo-5-hexenoate). The trans-ACOHDA hydrolase was induced after growth of Pseudomonas sp. BN9 with 5AS, but not after growth with acetate or nutrient broth. At the fumarylpyruvate stage, the metabolism of 5AS converged with a pathway described for the degradation of gentisate. Fumarylpyruvate was cleaved by Pseudomonas sp. BN9 to fumarate and pyruvate.

Acids↗

PubMed1993

5-hydroxyquinoline-2-carboxylic Acid, a dead-end metabolite from the bacterial oxidation of 5-aminonaphthalene-2-sulfonic Acid.

5-Aminonaphthalene-2-sulfonate (5A2NS) is converted by strain BN6 into 5-hydroxyquinoline-2-carboxylate (5H2QC). The authenticity of this new compound is confirmed by nuclear magnetic resonance and mass spectrometry. Its formation is explained by a spontaneous cyclization of the hypothetical metabolite 6'-amino-2'-hydroxybenzalpyruvate. The formation of 5H2QC as a dead-end product of 5A2NS prevents NADH regeneration so that 5A2NS oxidation is limited by the internal NADH pool.

Journal Article↗

PubMed1993

Dienelactone hydrolase from Pseudomonas cepacia.

Dienelactone hydrolases have previously been shown to play a crucial role in chlorocatechol degradation via the modified ortho cleavage pathway. Recently, the enzymes induced in 4-fluorobenzoate-utilizing bacteria have been classified into three groups on the basis of their specificity towards cis- and trans-dienelactone. The dienelactone hydrolase and the 3-oxoadipate enol-lactone hydrolase from Pseudomonas cepacia have now been purified to apparent homogeneity and characterized with respect to molecular mass and amino acid composition. The dienelactone hydrolase has a distinct preference for cis-dienelactone and did not convert the trans isomer or muconolactone, 3-oxoadipate enol-lactone, or 4-fluoromuconolactone to a significant extent. In properties like amino acid composition, pH optimum of activity, and lack of inhibition by p-chloromercuribenzoate, the P. cepacia dienelactone hydrolase differed substantially from 3-oxoadipate enol-lactone hydrolases and other dienelactone hydrolases.

Amino Acid Sequence↗

PubMed1992

Bacterial metabolism of 5-aminosalicylic acid. Initial ring cleavage.

The metabolism of 5-aminosalicylate (5AS) by a bacterial strain, Pseudomonas sp. BN9, was studied. Intact cells of Pseudomonas sp. BN9 grown with 5AS oxidized 5AS and 2,5-dihydroxybenzoate (gentisate), whereas cells grown with gentisate oxidized only the growth substrate of all substituted salicylates tested. Cell extracts from Pseudomonas sp. BN9 catalysed the stoichiometric reaction of 1 mol of oxygen with 1 mol of 5AS to a metabolite with an intense u.v.-absorption maximum at 352 nm (pH 8.0). This metabolite was accumulated under neutral conditions, but was rapidly destroyed at acid pH. It was identified by m.s. and acid-catalysed deamination to fumarylpyruvate (trans-2,4-dioxohept-5-enedioic acid) as cis-4-amino-6-carboxy-2-oxohexa-3,5-dienoate, thus demonstrating direct cleavage of the monohydroxylated substrate 5AS to a non-aromatic ring-fission product. The enzyme responsible for conversion of 5AS was shown to be Fe(II)-dependent and to be distinct from gentisate 1,2-dioxygenase in strain BN9.

Aminosalicylic Acids↗

PubMed1992

Degradation of 2,4-dinitrophenol by two Rhodococcus erythropolis strains, HL 24-1 and HL 24-2.

Two Rhodococcus erythropolis strains, HL 24-1 and HL 24-2, were isolated from soil and river water by their abilities to utilize 2,4-dinitrophenol (0.5 mM) as the sole source of nitrogen. Although succinate was supplied as a carbon and energy source during selection, both isolates could utilize 2,4-dinitrophenol also as the sole source of carbon. Both strains metabolized 2,4-dinitrophenol under concomitant liberation of stoichiometric amounts of nitrite and 4,6-dinitrohexanoate as a minor dead-end metabolite.

2,4-Dinitrophenol↗

PubMed1992

Initial hydrogenation during catabolism of picric acid by Rhodococcus erythropolis HL 24-2.

Rhodococcus erythropolis HL 24-2, which was originally isolated as a 2,4-dinitrophenol-degrading bacterium, could also utilize picric acid as a nitrogen source after spontaneous mutation. During growth, the mutant HL PM-1 transiently accumulated an orange-red metabolite, which was identified as a hydride-Meisenheimer complex of picric acid. This complex was formed as the initial metabolite and further converted with concomitant liberation of nitrite. 2,4,6-Trinitrocyclohexanone was identified as a dead-end metabolite of the degradation of picric acid, indicating the addition of two hydride ions to picric acid.

Biodegradation, Environmental↗

PubMed1991

Metabolism of naphthalene by the biphenyl-degrading bacterium Pseudomonas paucimobilis Q1.

Pseudomonas paucimobilis Q1 originally isolated as biphenyl degrading organism (Furukawa et al. 1983), was shown to grow with naphthalene. After growth with biphenyl or naphthalene the strain synthesized the same enzyme for the ring cleavage of 2,3-dihydroxybiphenyl or 1,2-dihydroxynaphthalene. The enzyme, although characterized as 2,3-dihydroxybiphenyl dioxygenase (Taira et al. 1988), exhibited considerably higher relative activity with 1,2-dihydroxynaphthalene. These results demonstrate that this enzyme can function both in the naphthalene and biphenyl degradative pathway.

Biodegradation, Environmental↗

PubMed1991

Catabolism of 1,3-dinitrobenzene by Rhodococcus sp. QT-1.

The 1,3-dinitrobenzene-degrading Rhodococcus strain QT-1 was isolated under nitrogen limiting conditions from contaminated soil samples. Experimental data indicate tha 1,3-dinitrobenzene is metabolized via 4-nitrocatechol. Both compounds were oxidized by resting cells and nitro groups were completely eliminated as nitrite. Strain QT-1 utilizes both 1,3-dinitrobenzene and 4-nitrocatechol as source of nitrogen in the absence as well as in the presence of high amounts of ammonia. Growth on 4-nitrocatechol does not induce the enzyme(s) for the initial oxidation of 1,3-dinitrobenzene.

Biodegradation, Environmental↗

PubMed1991

Mineralization of the sulfonated azo dye Mordant Yellow 3 by a 6-aminonaphthalene-2-sulfonate-degrading bacterial consortium.

Under anaerobic conditions the sulfonated azo dye Mordant Yellow 3 was reduced by the biomass of a bacterial consortium grown aerobically with 6-aminonaphthalene-2-sulfonic acid. Stoichiometric amounts of the aromatic amines 6-aminonaphthalene-2-sulfonate and 5-aminosalicylate were generated and excreted into the medium. After re-aeration of the culture, these amines were mineralized by different members of the bacterial culture. Thus, total degradation of a sulfonated azo dye was achieved by using an alternating anaerobic-aerobic treatment. The ability of the mixed bacterial culture to reduce the azo dye was correlated with the presence of strain BN6, which possessed the ability to oxidize various naphthalenesulfonic acids. It is suggested that strain BN6 has a transport system for naphthalenesulfonic acids which also catalyzes uptake of sulfonated azo dyes. These dyes are then gratuitously reduced in the cytoplasm by unspecific reductases.

Aerobiosis↗