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71.
A new bacterial alcohol dehydrogenase active on degraded lignin and several low molecular weight aromatic compounds 总被引:1,自引:0,他引:1
Jean Pelmont Catherine Tournesac Ahmed Mliki Michel Barrelle Claude Beguin 《FEMS microbiology letters》1989,57(1):109-114
A new intracellular bacterial dehydrogenase has been purified. It was active in the reversible reduction by NADH of conjugated carbonyl groups in partially degraded lignin. It was also active on various aromatic aldehydes such as vanillin, syringaldehyde and cinnamaldehyde, but had no effect on acetovanillone and lignin models carrying a conjugated ketone. It is proposed that this enzyme functions as a broadly specific lignin dehydrogenase at the level of aldehydic groups that are present in the lignin preparations. 相似文献
72.
Cysteine: Depolarization-Induced Release from Rat Brain In Vitro 总被引:3,自引:2,他引:1
Hans Jörg Keller Kim Quang Do Markus Zollinger Kaspar H. Winterhalter Michel Cuénod 《Journal of neurochemistry》1989,52(6):1801-1806
Compounds released on depolarization in a Ca2+-dependent manner from rat brain slices were screened to identify candidates for neuroactive substances. Lyophilized superfusates were analyzed by reversed-phase HPLC after derivatization with 9-fluorenyl N-succinimidyl carbonate. One of the compounds that showed an increase of concentration in superfusates in the presence of iodoacetamide was identified as the cysteine (Cys) derivative, S-carboxamidomethylcysteine, by fast atom bombardment mass spectrometry and other methods. This stable Cys derivative originates from endogenous, extracellular Cys. The finding led to a method for quantification of Cys in superfusates by immediate cooling of the superfusates to 0 degrees C and reaction of Cys with N-ethylmaleimide. Depolarization-induced Ca2+-dependent release of Cys was most prominent in the neocortex, followed by the mesodiencephalon, striatum, and cerebellum. This suggests that Cys is released from a neuronal compartment and might be involved in neurotransmission. 相似文献
73.
Véronique Guellec Chantal David Michel Branchard Jacques Tempé 《Plant Cell, Tissue and Organ Culture》1990,20(3):211-215
Genetically transformed grapevine (Vitis vinifera L.) roots were obtained after inocultation of in vitro grown whole plants (cv. Grenache) with Agrobacterium rhizogenes. The strain used contains two plasmids: the wild-type Ri plasmid pRi 15834 and a Ti-derived plasmid which carries a chimaeric neomycin phosphotrans-ferase gene (NPT II) and the nopaline synthase gene. Expression of the NPT II gene can confer kanamycin resistance to transformed plant cells. Slowly growing axenic root cultures derived from single root tips were obtained. Opine analysis indicated the presence of agropine and/or nopaline in established root cultures. For one culture, the presence of T-DNA was confirmed by dot-blot hybridization with pRi 15834 TL-DNA. Callogenesis was induced by subculturing root fragments on medium supplemented with benzylaminopurine and indoleacetic acid.Transformation of in vitro cultured grapevine cells has recently been reported (baribault T.J. et al., Plant Cell Rep (1989) 8: 137–140). In contrast with the results presented here, expession of the NPT II gene Conferred kanamycin resistance to Vitis vinifera calli that was sufficient for selection of trasformed cells.Abbreviations BAP
benzylaminopurine
- IAA
indoleacetic acid
- NAA
naphtaleneacetic acid
- NPT II
neomycin phosphostransferase II
- EDTA
ethylenediaminetetraacetic acid 相似文献
74.
Pascale Andre Christian Capo Anne Marie Benoliel Michel Buferne Pierre Bongrand 《Cell biochemistry and biophysics》1990,16(1-2):13-34
Fluorescent probes are widely used to study cell structure and function. However, few reports were devoted to a quantitative analysis of the intracellular distribution of fluorescent markers. In the present work, we describe the topographical changes of surface and cytoskeletal markers on individual cells subjected to adhesive or mechanical interaction. Conjugates were prepared with a cytotoxic T-lymphocyte clone and target cells. Specific antigens, membrane phospholipids, surface glycoconjugates, and polymerized actin were labeled with fluorescent antibodies or biochemical probes. The analysis of fluorescence distributions in conjugates demonstrated a selective reorganization of the plasma membrane with a gathering of some molecular species in the intercellular adhesion area. Furthermore, individual phagocytic cells were sucked into glass micropipets, then stained with fluorescent phallacidin to analyze the effect of mechanical efforts on the cytoskeleton organization. The concentration of polymerized actin was found to be similar in mechanicallyinduced protrusions and whole cells. It is concluded that adhesive interactions may result in marked cell polarization and formation of membrane zones with a particular biochemical composition. The submembranar cytoskeleton might play a role in this process. 相似文献
75.
The inhibitory effects of synthetic phenolic compounds on benzo(a)pyrene-induced neoplasia of the mouse forestomach have been measured by Wattenberg et al6 The efficiency of this inhibition has been estimated for each phenol, using R, the ratio of the number of tumors per mouse in the protected group over the number of tumours per mouse in the control group. We have observed a linear correlation between the chemoprotection efficiency R and the logarithm of the rate of quenching of singlet oxygen. k. by this family of phenols, log k being itself correlated with the one-electron oxidation potential of the phenols. These correlations suggest a charge transfer mechanism for the inhibition of neoplasia induced hy benzo(a)py-rene. The correlations described provide a theoretical basis for scaling the inhibitors of mutagenicity induced by polycyclic aromatic compounds in terms of their oxidation potentials 相似文献
76.
77.
78.
Dominique Le Grand Michel Solsona Renate Rosengarten francois Poumarat 《FEMS microbiology letters》1996,144(2-3):267-275
Abstract The variability of predominant Mycoplasma bovis surface antigens in the presence of specific immune pressure was analyzed in an in vitro assay to determine if M. bovis could escape immune destruction. We have shown that serum antibodies from immunized or experimentally infected calves and monoclonal antibodies which specifically react with previously characterized or as yet undefined major M. bovis membrane surface proteins cause repression of expression or shortening of the target protein, or induce switching to expression of an antigenically distinct variant protein. We have further demonstrated that removal of the inducing antibody results in reversion to the original phenotype. These results suggest that the level of expression and the length of M. bovis surface antigens in the host is modulated by cognate antibodies. According to the surface antigenic variation systems, random selection of preexisting variants resistant to antibody-mediated inhibition or direct regulation of gene expression may be means by which this organism evades host immune defences. 相似文献
79.
Signalling by protein kinase C isoforms in the heart 总被引:11,自引:0,他引:11
Understanding transmembrane signalling process is one of the major challenge of the decade. In most tissues, since Fisher and Krebs's discovery in the 1950's, protein phosphorylation has been widely recognized as a key event of this cellular function. Indeed, binding of hormones or neurotransmitters to specific membrane receptors leads to the generation of cytosoluble second messengers which in turn activate a specific protein kinase. Numerous protein kinases have been so far identified and roughly classified into two groups, namely serine/threonine and tyrosine kinases on the basis of the target amino acid although some more recently discovered kinases like MEK (or MAP kinase kinase) phosphorylate both serine and tyrosine residues.Protein kinase C is a serine/threonine kinase that was first described by Takai et al. [1] as a Ca- and phospholipid-dependent protein kinase. Later on, Kuo et al. [2] found that PKC was expressed in most tissues including the heart. The field of investigation became more complicated when it was found that the kinase is not a single molecular entity and that several isoforms exist. At present, 12 PKC isoforms and other PKC-related kinases [3] were identified in mammalian tissues. These are classified into three groups. (1) the Ca-activated -, -,and -PKCs which display a Ca-binding site (C2); (2) the Ca-insensitive -, -, -, -, and -PKCs. The kinases that belong to both of these groups display two cystein-rich domains (C1) which bind phorbol esters (for recent review on PKC structure, see [4]). (3) The third group was named atypical PKCs and include , , and -PKCs that lack both the C2 and one cystein-rich domain. Consequently, these isoforms are Ca-insensitive and cannot be activated by phorbol esters [5]. In the heart. evidence that multiple PKC isoforms exist was first provided by Kosaka et al. [6] who identified by chromatography at least two PKC-related isoenzymes. Numerous studies were thus devoted to the biochemical characterization of these isoenzymes (see [7] for review on cardiac PKCs) as well as to the identification of their substrates.This overview aims at updating the present knowledge on the expression, activation and functions of PKC isoforms in cardiac cells. (Mol Cell Biochem 157: 65–72, 1996) 相似文献
80.
The role of the N-terminus of the extrinsic 33 kDa protein of Photosystem II has been investigated by means of site-directed mutagenesis and cross-linking. Replacement of Asp-9 resulted in a dramatic increase in proteolytic sensitivity leading to the degradation of the protein forming a 31 kDa fragment with an undefined N-terminus. This fragment was unable to restore oxygen evolution. However, the variants of the 33 kDa protein which remained intact could reconstitute oxygen evolution as effectively as the wild-type protein. Cross-linking experiments with a water-soluble carbodiimide revealed that mutagenesis of residue D9 led to the disruption of an intramolecular salt bridge. Therefore we suggest that the N-terminus of the 33 kDa protein is necessary for maintaining the binding ability of the protein to Photosystem II but might not be involved in binding itself. 相似文献