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A Habenicht

Publications and source records attributed to A Habenicht.

12 recordsLinked to original sources
PubMed2005

Jumping nanodroplets.

Flat gold nanostructures on inert substrates like glass or graphite were illuminated by single intensive laser pulses with fluences above the gold melting threshold. The liquid structures produced in this way are far from their equilibrium shape, and a dewetting process sets in. On a time scale of a few nanoseconds, the liquid contracted toward a sphere. During this contraction, the center of mass moved upward, which could lead to detachment of droplets from the surface due to inertia. The resulting velocities were on the order of 10 meters per second for droplets with radii in the range of 100 nanometers.

Journal Article↗
PubMed1999

Xylose utilisation: cloning and characterisation of the Xylose reductase from Candida tenuis.

Xylose reductases catalyse the initial reaction in the xylose utilisation pathway, the NAD(P)H+H+ dependent reduction of xylose to xylitol. In this work, the xylose reductase gene from Candida tenuis CBS 4435 was cloned and successfully expressed in E. coli. From the purified and partially sequenced protein primers were deduced for PCR. The fragment obtained was used for Southern blot analysis and screening of a subgenomic library. The clone containing the open reading frame was sequenced; the gene consisted of 969 nucleotides coding for a 322 amino acids protein with a molecular mass of 36 kDa. Putative regulatory signals were identified with the help of a Saccharomyces cerevisiae regulatory sequence database. In order to express the xylose reductase in E. coli, the gene was placed under positive and negative control. At low temperatures, the xylose reductase was expressed in soluble and active form up to about 10% of the soluble protein; with rising temperatures formation of visible inclusion bodies occurred. In refolding experiments we were able to recover the major portion of xylose reductase activity from the pellet fraction.

Aldehyde Reductase↗
PubMed1999

Xylose utilisation: cloning and characterisation of the xylitol dehydrogenase from Galactocandida mastotermitis.

We cloned and successfully expressed the gene for xylitol dehydrogenase from Galactocandida mastotermitis in Escherichia coli. The amino acid sequence revealed that the enzyme belongs to the superfamily of zinc containing, medium-chain alcohol dehydrogenases. The enzyme catalyses the second step in the xylose utilising pathway converting xylose to xylulosephosphate. Xylulose-phosphate is further degraded by the transaldolase and transketolase reactions of the pentose phosphate pathway. The purified xylitol dehydrogenase from G. mastotermitis was subjected to partial amino acid sequence analysis. The resulting amino acid information was then used to construct oligonucleotide probes for PCR amplification. The PCR product was used to screen a genomic library. The identified xdh gene includes one short intron at its 5' end. Putative regulatory signals were identified with the help of Saccharomyces cerevisiae regulatory sequence databases. An intronless xdh transcript, cloned by RT-PCR, was actively expressed in pBTac1 at 37 degrees C to approximately 8% of the soluble E. coli protein. Furthermore, the kinetic parameters were determined and conditions were found to stabilise the soluble and active protein.

Amino Acid Sequence↗
PubMed1998

Molecular evolution of hydantoinases.

The complete amino acid sequence of the hydantoinase from Arthrobacter aurescens DSM 3745 has been derived by automated Edman degradation. This is the first ever reported amino acid sequence of a non-ATP-dependent hydantoinase, which hydrolyzes 5'-monosubstituted hydantoin derivatives L-selectively. A homology search performed in protein and nucleic acid databases retrieved only distantly related proteins. All of these are members of the recently described protein superfamily of amidohydrolases related to ureases (Holm and Sander, Proteins 28: 72-82, 1997). Phylogenetic analysis revealed that the novel hydantoinase forms a new branch separate from other hydantoin cleaving enzymes like dihydropyrimidinases (EC 3.5.2.2) and allantoinases (EC 3.5.2.5). Our results suggests that the enzymes of this protein superfamily have evolved from a common ancestor and therefore are the product of divergent evolution. We show further that the enclosed gene families developed very early in evolution, probably prior to the formation of the three domains, Archaea, Eukarya and Bacteria. Hydantoinases related to ATP-dependent N-methylhydantoinases (EC 3.5.2.14) or 5-oxoprolinases (EC 3.5.2.9) do not belong to this superfamily.

Amidohydrolases↗
PubMed1997

Sequence of the non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase from Nicotiana plumbaginifolia and phylogenetic origin of the gene family.

A cDNA-library has been constructed from Nicotiana plumbaginifolia seedlings, and the non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (GapN, EC 1.2.1.9) was isolated by plaque hybridization using the cDNA from pea as a heterologous probe. The cDNA comprises the entire GapN coding region. A putative polyadenylation signal is identified. Phylogenetic analysis based on the deduced amino acid sequences revealed that the GapN gene family represents a separate ancient branch within the aldehyde dehydrogenase superfamily. It can be shown that the GapN gene family and other distinct branches of the superfamily have its phylogenetic origin before the separation of primary life-forms. This further demonstrates that already very early in evolution, a broad diversification of the aldehyde dehydrogenases led to the formation of the superfamily.

Aldehyde Dehydrogenase↗
PubMed1997

The non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase: biochemistry, structure, occurrence and evolution.

The non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase catalyses the irreversible reaction of glyceraldehyde-3-phosphate to 3-phosphoglycerate by the reduction of NADP to NADPH. This is in contrast to the extensively analysed phosphorylating glyceraldehyde-3-phosphate dehydrogenases which catalyse the reversible reaction of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate. Sequence analysis revealed that the non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase is not related to the phosphorylating glyceraldehyde-3-phosphate dehydrogenases but a member of the aldehyde dehydrogenase superfamily. The aldehyde dehydrogenases are of ancient origin and they have already existed in the progenote as indicated by phylogenetic analysis. Thus the non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase can be found in all three domains, archaea, bacteria and eukarya. The catalytic mechanism of the non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase and the other aldehyde dehydrogenases resembles a thioester mechanism involving the universally conserved cysteine 298 (pea GAPN). The cofactor of the aldehyde dehydrogenases is bound in a new mode to a structure described as beta-alpha,beta-fold.

Amino Acid Sequence↗
PubMed1994

Non-phosphorylating GAPDH of higher plants is a member of the aldehyde dehydrogenase superfamily with no sequence homology to phosphorylating GAPDH.

Non-phosphorylating glyceraldehyde 3-phosphate dehydrogenase (GAPDH, NADP-specific, EC 1.2.1.9) operates in the cytosol of autotrophic eukaryotes where it generates NADPH for biosynthetic processes from photosynthetic glyceraldehyde 3-phosphate exported from the chloroplast by the phosphate translocator. Here we report the first cloning and characterization of cDNAs encoding complete polypeptide chains of nonphosphorylating GAPDH from pea and maize by using oligonucleotide probes derived from amino acid sequences determined for the purified enzyme. Unexpectedly, nonphosphorylating GAPDH cannot be aligned with the well-known sequences of phosphorylating GAPDH, but shares about 30% amino acid identity with various specialized and non-specialized aldehyde dehydrogenases (ALDHs) of eubacteria and eukaryotes. A phylogenetic analysis of this ALDH superfamily reveals a complex evolutionary pattern with numerous major branches carrying genes from eubacteria, eukaryotes, or both, encoding enzymes that are specific or non-specific for particular aldehyde substrates. This topology suggests a concomitant emergence of multiple substrate specificities from non-specialized ALDH during an early evolutionary phase of intense metabolic diversification. Although unrelated at the sequence level, non-phosphorylating aldehyde dehydrogenases and phosphorylating GAPDH resemble one another with respect to catalytic hydride transfer and covalent thiol ester formation. Whether or not this reflects an ancestral relationship can only be decided when crystallographic data for ALDH enzymes have become available.

Amino Acid Sequence↗
PubMed1993

Molecular cloning of the large subunit of glutathione synthetase from Xenopus laevis embryos.

We have isolated a cDNA clone from a Xenopus laevis tadpole cDNA library which probably codes for the large subunit of glutathione synthetase. The corresponding protein comprises 474 amino acids and shows a significant homology with the large subunit of glutathione synthetase of Schizosaccharomyces pombe. RNase protection experiments revealed that the gene is transcribed during oogenesis and that zygotic expression starts after midblastula transition. Transcripts are also detected in various adult tissues suggesting an ubiquitous distribution of the corresponding protein.

Amino Acid Sequence↗
PubMed1977

Improved assessment of plasma lipoprotein patterns. III. Direct measurement of lipoproteins after gel-electrophoresis.

Based on a previously described technique [Clin. Chem. 19, 737 (1973)] of precipitating plasma lipoproteins with polyanions after their electrophoretic separation in gels, a new method is presented for measuring normal plasma lipoproteins densitometrically. The method is fast and easy; the CV for beta-, pre-beta-, and alpha-lipoproteins was less than 5% in one series. Results are linearly related to concentration up to 10 g of total lipoprotein per liter. No unusual equipment is required. Standardization is done with the aid of a commercially available filter. Total plasma cholesterol and cholesterol calculated from quantified lipoprotein fractions were highly (r = 0.963) correlated.

Adult↗
PubMedDate not supplied

A new role for nicotine: selective inhibition of thromboxane formation by direct interaction with thromboxane synthase in human promyelocytic leukaemia cells differentiating into macrophages.

Thromboxane, one of the major oxygenated arachidonic acid metabolites of human macrophages, is the most potent vasoconstricting and proaggregatory molecule known. In addition, thromboxane has been shown to be related to host defence mechanisms. We studied the effects of nicotine and its major metabolites on thromboxane formation using cultured macrophage-like cells (HL-60), microsomal assays and purified thromboxane synthase. In intact cells, nicotine, cotinine and methylnicotine at submicromolar concentrations inhibited the rate of conversion of both arachidonic acid and the unstable endoperoxide prostaglandin H2 into thromboxane but not into other eicosanoids. This indicates that nicotine selectively inhibits thromboxane synthase at concentrations that are readily observed in the circulation of smokers. Microsomal assays revealed that nicotine decreased the maximal velocity of thromboxane synthase without affecting the apparent affinity of the enzyme for its substrate. In contrast, no effect of nicotine on kinetic parameters of prostaglandin H synthase or prostacyclin synthase could be observed. Difference spectra, using purified thromboxane synthase, revealed that nicotine directly interacts with the enzyme, presumably by binding the nitrogen of the nicotine ring structure to the iron of the cytochrome P-450 component of thromboxane synthase.

6-Ketoprostaglandin F1 alpha↗