摘要:

Sulfur removal from petroleum is important from the standpoint of the global environment because the combustion of sulfur compounds leads to the production of sulfur oxides, which are the source of acid rain. As the regulations for sulfur in fuels become more stringent, the existing chemical desulfurizations are coming inadequate for the “deeper desulfurization” to produce lower-sulfur fuels without new and innovative processes. Biodesulfurization is rising as one of the candidates. Several microorganisms were found to desulfurize dibenzothiophene (DBT), a representative of the organic sulfur compounds in petroleum, forming a sulfur-free compound, 2-hydroxybiphenyl. They are promising as biocatalysts in the microbial desulfurization of petroleum because without assimilation of the carbon content, they remove only sulfur from the heterocyclic compounds which is refractory to conventional chemical desulfurization. Both enzymological and molecular genetic studies are now in progress for the purpose of obtaining improved desulfurization activity of organisms. The genes involved in the sulfur-specific DBT desulfurization were identified and the corresponding enzymes have been investigated. From the practical point of view, it has been proved that the microbial desulfurization proceeds in the presence of high concentrations of hydrocarbons, and more complicated DBT analogs are also desulfurized by the microorganisms. This review outlines the progress in the studies of the microbial desulfurization from the basic and practical point of view.

ISSN:0916-8451    

DOI:10.1271/bbb.63.1

出版商:Japan Society for Bioscience, Biotechnology, and Agrochemistry    

年代:1999

数据来源: Taylor

摘要:

Resting cells ofAcetobacter pasteurianusLMG 1635 (ATCC 12874) show appreciable enantioselectivity (E=16-18) in the oxidative kinetic resolution of racemic 2,3-epoxy-1-propanol, glycidol. Distinctly lower values (E=7-9) are observed for the ferricyanide-coupled oxidation of glycidol by the isolated quinohemoprotein alcohol dehydrogenase, QH-ADH, which is responsible for the enantiospecific oxidation step in whole cells. The accuracy ofE-values from conversion experiments could be verified using complementary methods for the measurement of enantiomeric ratios. Effects of pH, detergent, the use of artificial electron acceptors, and the presence of intermediate aldehydes, could be accounted for. Measurements ofE-values at successive stages of the purification showed that the drop in enantioselectivity correlates with the separation of QH-ADH from the cytoplasmic membrane. It is argued that the native arrangement of QH-ADH in the membrane-associated complex favors the higherE-values. The consequences of these findings for the use of whole cells versus purified enzymes in biocatalytic kinetic resolutions of chiral alcohols are discussed.

ISSN:0916-8451    

DOI:10.1271/bbb.63.10

出版商:Japan Society for Bioscience, Biotechnology, and Agrochemistry    

年代:1999

数据来源: Taylor

摘要:

A genetically engineered fusion enzyme between rat P4501A1 and yeast P450 reductase in the microsomal fraction of the recombinant yeast AH22/pAFCR1 was purified. The purified enzyme showed a typical CO-difference spectrum of P4501A1 and a single band with an apparent molecular weight of 125,000 on sodium dodecyl sulfate polyacrylamide gel electrophoresis. This agreed with the molecular weight of 131,202 calculated from the amino acid sequence. The purified enzyme showed both 7-ethoxycoumarino-deethylase activity and horse heart cytochromecreductase activity in the presence of NADPH. The 7-ethoxycoumarino-deethylase activity depended on the species of lipid used for the reconstitution of the purified fusion enzyme although the purified enzyme showed the activity without reconstitution. The purified fusion enzyme had the Km value of 26 μMfor 7-ethoxycoumarin and the maximal turnover rate of 29 mol product/min/mol enzyme at 30°C.

ISSN:0916-8451    

DOI:10.1271/bbb.63.21

出版商:Japan Society for Bioscience, Biotechnology, and Agrochemistry    

年代:1999

数据来源: Taylor

摘要:

Apolipoprotein A-I (apo A-I) has an important role in the transport of cholesterol. This study describes the complete nucleotide and deduced amino acid sequence for apo A-I of LAP quail. A full length apo A-I cDNA clone for hyperlipidemia atherosclerosis prone (LAP) quail was isolated from a λgt10 liver cDNA library. The DNA sequence of LAP apo A-I cDNA was similar to that of normal Japanese quail. The deduced amino acid sequence of LAP apo A-I was hence identical to that of normal Japanese quail. LAP apo A-I mRNA is about 1.4 kilobases in length and expressed in a variety of tissues including small intestine, liver, lung, breast muscle, testis, and heart. Although the tissue distribution of apo A-I was similar between strains, LAP quail expressed more apo A-I mRNA than normal Japanese quail in all tissues examined. This tendency was pronounced with the small intestine. Although the concentration of serum apo A-I did not correlate with the tissue expression of mRNA, the observation may suggest that the increased apo A-I expression in LAP strain had some relevance to the susceptibility of this strain to the experimental atherosclerosis.

ISSN:0916-8451    

DOI:10.1271/bbb.63.29

出版商:Japan Society for Bioscience, Biotechnology, and Agrochemistry    

年代:1999

数据来源: Taylor

摘要:

The structures ofN-linked sugar chains of glycoproteins expressed in tobacco BY2 cultured cells are reported. Five pyridylaminated (PA-)N-linked sugar chains were derived and purified from hydrazinolysates of the glycoproteins by reversed-phase HPLC and size-fractionation HPLC. The structures of the PA-sugar chains purified were identified by two-dimensional PA-sugar chain mapping, ion-spray MS/MS analysis, and exoglycosidase digestions. The five structures fell into two categories; the major class (92.5% as molar ratio) was a xylose containing-type (Man3Fuc1Xyl1GlcNAc2(41.0%), GlcNAc2Man3Fuc1Xyl1GlcNAc2(26.5%), GlcNAc1Man3Fuc1Xyl1GlcNAc2(21.7%), Man3Xyl1GlcNAc2(3.3%)), and the minor class was a high-mannose type (Man5GlcNAc2(7.5%)). This is the first report to show that α(1→3) fucosylation ofN-glycans does occur but β(1→4) galactosylation of the sugar chains does not in the tobacco cultured cells.

ISSN:0916-8451    

DOI:10.1271/bbb.63.35

出版商:Japan Society for Bioscience, Biotechnology, and Agrochemistry    

年代:1999

数据来源: Taylor

摘要:

Fossil shellfish powder (FS) and Ezo giant scallop shell powder (EG) were rendered soluble with lactate and citrate under decompression (FSEx and EGEx, respectively) and we examined the effects of lactate-citrate solubilization of FS and EG on mineral absorption, tissue mineral contents, serum biochemical indices and bone mineral density (BMD) in ovariectomized (OVX) rats. The apparent absorption ratios of minerals tended to be high in the rats fed with the solubilized mineral sources, those in the FSEx group being significantly higher than in the FS group. There was no significant difference in the tibia mineral content among the OVX groups. BMD at the distal femoral diaphysis was significantly increased by FSEx and EGEx feeding. It is suggested that solubilization with lactate and citrate under decompression increased the solubility and bioavailability of calcium from such natural sources of shellfish calcium as FS and EG.

ISSN:0916-8451    

DOI:10.1271/bbb.63.40

出版商:Japan Society for Bioscience, Biotechnology, and Agrochemistry    

年代:1999

数据来源: Taylor

摘要:

Gluconobacter oxydansDSM 4025 effectively oxidizesL-sorbose to 2-keto-L-gulonic acid (2 KGA), an industrial precursor of vitamin C. From this microorganism, we purified the enzyme involved in this oxidation reaction. The enzyme is a unique quinoprotein dehydrogenase catalyzing not only the conversion ofL-sorbose toL-sorbosone, but also that ofL-sorbosone to 2 KGA. The molecular weight of the enzyme was about 135,000, consisting of two subunits with molecular weights of 64,500 and 62,500. As its prosthetic group, non-covalently bound PQQ was found. The dye-linked spectrophotometric enzyme assay showed that the optimum enzyme activity occurred in the pH range about 7.0-9.0, and the enzyme activity was inhibited by EDTA or EGTA. The enzyme showed extremely broad substrate specificity for primary and secondary alcohols, aldehydes, aldoses, ketoses, and other sugar alcohols, but not for methanol or formaldehyde. The cytochromecobtained from the soluble fraction of this strain was found to act as a physiological electron acceptor of the enzyme.

ISSN:0916-8451    

DOI:10.1271/bbb.63.46

出版商:Japan Society for Bioscience, Biotechnology, and Agrochemistry    

年代:1999

数据来源: Taylor

摘要:

The effects of superoxide dismutase (SOD) and catalase on the autoxidation rate ofL-ascorbic acid (ASA) in the absence of metal ion catalysts were examined. The stabilization of ASA by SOD was confirmed, and the enzyme activity of SOD, which scavenges the superoxide anion formed during the autoxidation of ASA, contributed strongly to this stabilization. The stabilization of ASA by catalase was observed for the first time; however, the specific enzyme ability of catalase would not have been involved in the stabilization of ASA. Such proteins as bovine serum albumin (BSA) and ovalbumin also inhibited the autoxidation of ASA, therefore it seems that non-specific interaction between ASA and such proteins as catalase and BSA might stabilize ASA and that the non-enzymatic superoxide anion scavenging ability of proteins might be involved.

ISSN:0916-8451    

DOI:10.1271/bbb.63.54

出版商:Japan Society for Bioscience, Biotechnology, and Agrochemistry    

年代:1999

数据来源: Taylor

摘要:

We cloned and analyzed the nucleotide sequence of a cDNA that encodes polyphenol oxidase (laccase) from the white-rot basidiomyceteSchizophyllum commune.The nucleotide sequence of the full-length cDNA contained a 1554-base open reading frame that encoded a polypeptide of 518 amino acid residues, including a putative signal peptide of 16 residues. It contained four highly similar regions that are conserved in the deduced amino acid sequences of other laccases, including the region thought to be involved in copper binding.Aspergillus sojaestrain 1860 (which has low protease levels) was transformed with the plasmid lacAL/pTPT, which contained the laccase gene under the control of the tannase promoter fromAspergillus oryzae. Laccase was secreted into the medium when transformants A1 and A2 were cultured in tannic acid-containing medium.

ISSN:0916-8451    

DOI:10.1271/bbb.63.58

出版商:Japan Society for Bioscience, Biotechnology, and Agrochemistry    

年代:1999

数据来源: Taylor

摘要:

A low-molecular-weight, high-alkaline pectate lyase (pectate transeliminase, EC 4.2.2.2) was found in an alkaline culture ofBacillussp. strain KSM-P15, purified to homogeneity, and crystallized. The enzyme had a relative molecular weight of approximately 20,300 as measured by sedimentation equilibrium, with a sedimentation coefficient (s20,w0) of 1.73S. It was a basic protein with an isoelectric point of pH 10.3, and the α-helical content was only 6.6%. In the presence of Ca2+ions, the enzyme degraded polygalacturonic acid in a random manner to yield 4,5-unsaturated oligo-galacturonides and had its optimal activity around pH 10.5 and 50-55°C. It also had a protopectinase-like activity on cotton fibers. TheN-terminal amino acid sequences of the intact protein (28 amino acids) and its two lysyl endopeptidase-cleaved peptide fragments (8 and 12 amino acids) had very low sequence similarity with pectate lyases reported to date. These results strongly suggest that the pectate lyase ofBacillussp. strain KSM-P15 may be a novel enzyme and belongs in a new family.

ISSN:0916-8451    

DOI:10.1271/bbb.63.65

出版商:Japan Society for Bioscience, Biotechnology, and Agrochemistry    

年代:1999

数据来源: Taylor