Degradation of some phenols and hydroxybenzoates by the imperfect ascomycetous yeastsCandida parapsilosis andArxula adeninivorans: evidence for an operative gentisate pathway

The imperfect ascomycetous yeastsCandida parapsilosis andArxula adeninivorans degraded 3-hydroxybenzoic acid via gentisate which was the cleavage substrate. 4-Hydroxybenzoic acid was metabolized via protocatechuate. No cleavage enzyme for the latter was detected. In stead of this NADH- and NADPH-dependent monooxygenases were present. In cells grown at the expense of hydroquinone and 4-hydroxygenzoic acid, enzymes of the hydroxyhydroquinone variant of the 3-oxoadipate pathway were demonstrated, which also took part in the degradation of 2,4-dihydroxybenzoic acid byC. parapsilosis.Abbreviations HHQ Hydroxyhydroquinone (1,2,4-trihydroxybenzene) - GSH reduced Glutathione     

Purification and characterization of delta helicase from fetal calf thymus.

A DNA helicase (delta helicase) which partially copurifies with DNA polymerase delta has been highly purified from fetal calf thymus. delta helicase differs in physical and enzymatic properties from other eukaryotic DNA helicases described thus far. The enzyme has an apparent mass of 57 kDa by gel filtration and is associated with polypeptides of 56 and 52 kDa by SDS-polyacrylamide gel electrophoresis. Photo-cross-linking of the purified enzyme with [alpha-32P]ATP resulted in labeling of a polypeptide of approximately 58 kDa, suggesting that the active site is present on the larger polypeptide. Unwinding of a partial duplex requires a nucleoside triphosphate which can be either ATP or dATP but not a nonhydrolyzable analogue of ATP. Other ribo- and deoxyribonucleoside triphosphates have little or no activity as cofactors. delta helicase also has DNA-dependent ATPase activity which has a relatively low Km for ATP (40 microM). delta helicase binds to single-stranded DNA but has little or no affinity for double-stranded DNA or single-stranded RNA. Similar to replicative DNA helicases from prokaryotes and the herpes simplex virus type 1 helicase-primase, delta helicase translocates in the 5'-3' direction along the strand to which it is bound and preferentially unwinds DNA substrates with a forklike structure.     

Inhibition of xanthine oxidase by uric acid and its influence on superoxide radical production.

The inhibition of xanthine oxidase by its reaction product, uric acid, was studied by steady state kinetic analysis. Uric acid behaved as an uncompetitive inhibitor of xanthine oxidase with respect to the reducing substrate, xanthine. Under 50 microM xanthine and 210 microM oxygen, the apparent K(i) for uric acid was 70 microM. Uric acid-mediated xanthine oxidase inhibition also caused an increase in the percentage of univalent reoxidation of the enzyme (superoxide radical production). Steady-state rate equations derived by the King-Altman method support the formation of an abortive-inhibitory enzyme-uric acid complex (dead-end product inhibition). Alternatively, inhibition could also depend on the reversibility of the classical ping-pong mechanism present in xanthine oxidase-catalyzed reactions.     

Growth effects of nagilactone E on cultured cells of lettuce

Nagilactone E, a norditerpene dilactone isolated from a gymnosperm, Podocarpus nagi (Podocarpaceae), was able to stimulate the growth of cultured cells of Lactuca sativa cv. Grand Rapids at 0.1 g ml^-1 but not at 0.01 or 1 g ml^-1. Cell wet weight/unit time and cell number/unit wet weight were increased when they were recorded at the end of the 14-day incubation period. Also, the population of cells treated with that concentration of nagilactone E had a higher percentage of cells with shorter cell length compared to the control (untreated).     

Preliminary study of the distribution of the toxic elements As,Cd, and Hg in human hair and tissues by RNAA

In order to study the relationships between trace element concentrations of hair and internal body burdens, a radiochemical NAA technique has been used for determination of the elements As, Cd, and Hg in autopsy samples of liver, kidney-cortex, lung, and hair from 24 male persons who died by accident. High significant positive correlations were observed between the As concentration in hair and in kidney-cortex, and between Cd and Zn concentrations in kidney-cortex. The contents of Cd, both for lung and kidney-cortex, were related to the smoking habits of the subjects.

     

A modular domain of NifU,a nitrogen fixation cluster protein,is highly conserved in evolution

HnifU, a gene exhibiting similarity tonifU genes of nitrogen fixation gene clusters, was identified in the course of expressed sequence tag (EST) generation from a human fetal heart cDNA library. Northern blot of human tissues and polymerase chain reaction (PCR) using human genomic DNA verified that the hnifU gene represented a human gene rather than a microbial contaminant of the cDNA library. Conceptual translation of the hnifU cDNA yielded a protein product bearing 77% and 70% amino acid identity to NifU-like hypothetical proteins fromHaemophilus influenzae andSaccharomyces cerevisiae, respectively, and 40–44% identity to the N-terminal regions of NifU proteins from several diazatrophs (i.e., nitrogen-fixing organisms). Pairwise determination of amino acid identities between the NifU-like proteins of nondiazatrophs showed that these NifU-like proteins exhibited higher sequence identity to each other (63–77%) than to the diazatrophic NifU proteins (40–48%). Further, the NifU-like proteins of non-nitrogenfixing organisms were similar only to the N-terminal region of diazatrophic NifU proteins and therefore identified a novel modular domain in these NifU proteins. These findings support the hypothesis that NifU is indeed a modular protein. The high degree of sequence similarity between NifU-like proteins from species as divergent as humans andH. influenzae suggests that these proteins perform some basic cellular function and may be among the most highly conserved proteins. Correspondence to: C.-C. Liew     

Characterization and expression of the plasmid-borne bedD gene from Pseudomonas putida ML2, which codes for a NAD+-dependent cis-benzene dihydrodiol dehydrogenase.

The catabolic plasmid pHMT112 in Pseudomonas putida ML2 contains the bed gene cluster encoding benzene dioxygenase (bedC1C2BA) and a NAD+-dependent dehydrogenase (bedD) required to convert benzene into catechol. Analysis of the nucleotide sequence upstream of the benzene dioxygenase gene cluster (bedC1C2BA) revealed a 1,098-bp open reading frame (bedD) flanked by two 42-bp direct repeats, each containing a 14-bp sequence identical to the inverted repeat of IS26. In vitro translation analysis showed bedD to code for a polypeptide of ca. 39 kDa. Both the nucleotide and the deduced amino acid sequences show significant identity to sequences of glycerol dehydrogenases from Escherichia coli, Citrobacter freundii, and Bacillus stearothermophilus. A bedD mutant of P. putida ML2 in which the gene was disrupted by a kanamycin resistance cassette was unable to utilize benzene for growth. The bedD gene product was found to complement the todD mutation in P. putida 39/D, the latter defective in the analogous cis-toluene dihydrodiol dehydrogenase. The dehydrogenase encoded by bedD) was overexpressed in Escherichia coli and purified. It was found to utilize NAD+ as an electron acceptor and exhibited higher substrate specificity for cis-benzene dihydrodiol and 1,2-propanediol compared with glycerol. Such a medium-chain dehydrogenase is the first to be reported for a Pseudomonas species, and its association with an aromatic ring-hydroxylating dioxygenase is unique among bacterial species capable of metabolizing aromatic hydrocarbons.     

中国单头螨属一新种(蜱螨亚纲：叶螨科)

中国单头螨属一新种（蜱螨亚纲：叶螨科）谭瑞成,鲁素玲（湖南省林业科学研究所长沙４１０００４）（新疆石河子农学院新疆８３２００３）单头螨属ＡｐｌｏｎｏｂｉａＷＯｍｅｒｓｌｅｙ,１９４０前足体背毛３对,后半体背毛１０对,全部或部分背毛着生在明显结节Ｌ,背...     

菠菜BADH单抗细胞株及其应用初探

用菠菜甜菜碱醛脱氢酶 ( BADH)免疫巴比西 ( BALB/c)小鼠 ,将其脾细胞与骨髓瘤细胞 SP2 /O-Ag1 4融合 ,在 1 92孔中 ,有约 1 4 %孔生长的杂交瘤细胞 ,用间接酶联免疫方法 ( ELISA)检测表现为阳性。选择其中 2 G3和 2 D10 细胞系 ,用有限稀释法进行克隆化培养 ,约 2 0 %克隆化细胞为强阳性。选择其中 2 G3- H3细胞株注射到 BALB/c小鼠腹腔中诱导腹水 ,腹水的单抗效价为 1∶ 1 0 3。应用 BADH单抗检查了大麦、水稻、高粱、小麦幼苗的叶片和根的粗提物 ,均呈阳性反应 ,表明 BADH除在光合组织中存在外 ,在非光合组织中也可能存在。讨论了非光合组织 BADH的意义