No abstract

A dibenzothiophene (DBT)-degrading bacterium, Rhodococcus erythropolis D-1, which utilized DBT as a sole source of sulfur, was isolated from soil. DBT was metabolized to 2-hydroxybiphenyl (2-HBP) by the strain, and 2-HBP was almost stoichiometrically accumulated as the dead-end metabolite of DBT degradation. DBT degradation by this strain was shown to proceed as DBT-* DBT sulfone-2-HBP. DBT at an initial concentration of 0.125 mM was completely degraded within 2 days of cultivation. DBT at up to 2.2 mM was rapidly degraded by resting cells within only 150 min. It was thought this strain had a higher DBTdesulfurizing ability than other microorganisms reported previously.

No abstract

Polyvinyl alcohol (PVA)-utilizing cultures were obtained from various sources. They were mixed cultures even after cyclical transfer to liquid and plate media with PVA as a sole source of carbon. Component bacteria were isolated from the several mixed cultures, and it was shown that PVA was utilized symbiotically by two bacterial members which could not utilize PVA in each respective pure culture. From a mixed culture, strains VM15, VM15A (Pseudomonasputida) and VM15C (Pseudomonas sp.) were isolated as members essential for PVA utilization. VM15C was the predominant strain in the mixed-culture population and produced PVA-degrading enzyme. The culture supernatant of VM15A enabled VM15C to grow on PVA. VM15A was presumed to supply VM15C with a unique growth stimulant which was distinct from usual growth factors.

Sm(Fe1−xMx)12 ternary compounds based on the tetragonal ThMn12 structure where M is Ti, Si, V, Cr, and Mo were investigated. M atoms have a preference for site occupation. Ti atoms occupy the 8i or 8j site and Cr atoms occupy the 8i site. Curie temperatures on Sm(M,Fe)12 compounds are around 590 K except for the SmMo2Fe10 compound (Tc=483 K). The SmTiFe11 and SmSi2Fe10 compounds have a high saturation magnetization and magnetic anisotropy.

A novel enzyme, formaldehyde dismutase, was purified and crystallized from the cell extract of an isolated bacterium, Pseudomonas putida F 61. The enzyme catalyzes the dismutation of aldehydes and alcohol: aldehyde oxidoreduction in the absence of an exogenous electron acceptor. The enzyme is composed of four identical subunits with a M, of 44000. Each subunit contains 1 mol NAD(H) and 2 mol zinc/mol. The ratio of NAD+ and NADH in a crystalline preparation of the enzyme was about 7: 3. The enzyme-bound coenzyme was completely reduced and oxidized on the addition of a large amount of an alcohol and an aldehyde respectively. Both the oxidized and reduced enzymes catalyzed the dismutation reaction to the same extent. Steady-state kinetics of the enzyme were investigated using an oxidoreduction reaction between an alcohol and p-nitroso-N,N-dimethylaniline. The enzyme obeys a ping-pong mechanism and is competitively inhibited by an alcoholic substrate analogue, pyrazole, but not coenzyme analogues, such as AMP, N-methylnicotinamide. These results indicate that NAD(H) binds firmly (but not covalently) at each active site. The enzyme-bound NAD(H) was reduced and oxidized only by the added second substrates, alcohol and aldehyde respectively, and not by exogenous electron acceptors [including NAD(H)].In the preceding studies [I -31 we found a novel enzyme, which was given the trivial name of formaldehyde dismutase, in an isolated bacterium, Pseudomonas putida F61. This enzyme catalyzed the dismutation of aldehydes (including formaldehyde), leading to the formation of equimolar amounts of the corresponding alcohols and acids. Preferable substrates,for the reaction were aldehydes that are hydrated to a great extent, such as formaldehyde, acetaldehyde and methylglyoxal. A variety of non-hydrated aldehydes was also reduced through the cross-dismutation with the hydrated aldehydes. Thus, the dismutation and cross-dismutation reactions can be seen as coupled oxidoreduction of an aldehyde (RCHO) and an 'alcohol' [RCH(OH),] formed through the hydration. Furthermore, this enzyme catalyzes the oxidoreduction of a natural alcohol and an aldehyde, leading to the exchange of the alcohol and aldehyde species. Analogous reactions with limited substrates have been reported to be catalyzed by native horse liver alcohol dehydrogenase in the presence of NAD [4-61, and by the dehydrogenase covalently bound an NAD analogue in the absence of an exogenous coenzyme [7, 81. However, formaldehyde dismutase, which is a naturally occurring bacterial enzyme, is distinct from these native and modified alcohol dehydrogenases in that it shows no requirement of an electron acceptor and there is no enhancement of its activity on the addition of an excess amount of NAD'. The oxidoreduction in the dismutation reaction is mediated by a non-dissociable coenzyme of this enzyme. In this work we report that the crystalline enzyme contains nonCorrespondence to N. Kato,

A 57 kbp SphI fragment containing the polyvinyl alcohol (PVA) dehydrogenase gene pvaA and its 19 kbp 5'-flanking region was cloned from the PVAdegrading bacterium Pseudomonas sp. VM15C. The pvaB gene, encoding oxidized PVA hydrolase, was found in the region upstream of pvaA. Sequence data and expression studies indicated that pvaA and B constitute an operon in the order pvaBA. The pvaB gene encoded a protein of 379 amino acid residues (40 610 Da), and a lipoprotein signal sequence and the lipase consensus sequence, Gly-X-Ser-X-Gly, characteristic of the active-site serine region in serine hydrolases, were detected in the deduced amino acid sequence. The pvaB product with the pvaA product constituted an enzyme system for the cleavage of PVA molecules. The pvaA product introduced β-diketone groups into the PVA molecule, and the pvaB product hydrolysed these β-diketone groups in oxidized PVA. The pvaB product also hydrolysed 4,6-nonanedione at a low rate, but not acetylacetone or 5-nonanone. It was completely inhibited by PMSF and was concluded to be a serine hydrolase. There were no proteins showing high similarity to the pvaB product in the databases, but minor similarity to a number of serine hydrolases including polyhydroxyalkanoate depolymerases was apparent.

Oxidized polyvinyl alcohol hydrolase (OPH) and polyvinyl alcohol dehydrogenase were found to be constitutively present in the periplasm of Sphingomonas sp. strain 113P3 (formerly Pseudomonas sp. 113P3). The OPH was purified to homogeneity with a yield of 40 % and a 5?9-fold increase in specific activity. The enzyme was a homodimer consisting of 35 kDa subunits. Its activity was inhibited by PMSF, Hg 2+ and Zn 2+. The enzyme hydrolysed oxidized polyvinyl alcohol (oxidized PVA) and p-nitrophenyl acetate (PNPA), but did not hydrolyse any of the mono-or diketones tested. K m and V max values for oxidized PVA and PNPA were 0?2 and 0?3 mM, and 0?1 and 3?4 mmol min "1 mg "1 , respectively. The gene for OPH was cloned and sequenced. Sequencing analysis revealed that the open reading frame consisted of 1095 bp, corresponding to a protein of 364 amino acids residues, encoding a signal peptide and a mature protein of 34 and 330 amino acids residues, respectively. The presence of a serine-hydrolase motif (a lipase box; Gly-X-Ser-X-Gly) strongly suggested that the enzyme belongs to the serine-hydrolase family. The protein exhibited homology with OPH of the Pseudomonas sp. strain VM15C (63 % identity) and the polyhydroxybutyrate depolymerases from Mesorhizobium loti, Rhizobium sp. and Sinorhizobium meliloti (29-32 % identity). The oph gene was expressed in Escherichia coli under the control of the lac promoter. The recombinant protein had the same molecular mass and N-terminal amino acid sequence as the purified OPH from strain 113P3.