Dolichol: a curriculum cognitionis

1992 ◽  
Vol 70 (6) ◽  
pp. 377-381 ◽  
Author(s):  
Frank W. Hemming
Keyword(s):  
Biosynthetic Pathway ◽  
Side Chain ◽  
Plant Tissues ◽  
Animal Tissues ◽  
Dolichyl Phosphate ◽  
Putative Precursor ◽  
Eukaryotic Organisms ◽  
Derivatives Of ◽  
Long Chain

Dolichols were first described about 30 years ago when animal tissues were being examined for the presence of a putative precursor to the polyisoprenoid side chain of ubiquinone. These long-chain 2,3-dihydro-polycis-isoprenoid alcohols are found in all eukaryotic organisms. In many plant tissues they are accompanied by families of other polyisoprenoid alcohols that are usually similar molecules and possess an unsaturated α-isoprene residue. Analogy with the role of bactoprenyl phosphates in the synthesis of bacterial wall glycans led to the discovery that the mono- and di-phosphates of dolichols function as cofactors in protein N-glycosylation, involving the formation of glycosylated derivatives of dolichol as intermediates. Variation of the concentration of dolichyl phosphate was shown to be one way of controlling protein N-glycosylation. This can be achieved by modification of the relative activities of dolichol kinase and dolichol phosphate phosphatase. Modulation of the biosynthetic pathway, still not fully understood, of dolichyl phosphate may also be an important factor. Several disease conditions involve aberrations in these pathways.Key words: dolichols, polyisoprenoid alcohols, N-glycosylation, O-mannosylation.

scholarly journals The breakdown and synthesis of starch by an enzyme system from pea seeds

1940 ◽  
Vol 128 (853) ◽  
pp. 421-450 ◽  
Keyword(s):  
Higher Plants ◽  
Enzyme System ◽  
Animal Tissues ◽  
Outstanding Achievement ◽  
Intermediary Role ◽  
Pea Seeds ◽  
Extensive Body ◽  
Phosphorylated Sugars ◽  
Derivatives Of

The gradual elucidation of the intermediary role of phosphorylated sugars in the breakdown of carbohydrate by the enzymes of yeast and certain animal tissues forms an outstanding achievement in the field of the biochemistry of carbohydrates. It is attractive to suppose that the rapid interconversions of carbohydrates which occur in the higher plants may depends also upon the formation of labile phosphorylated derivatives of sugars. It cannot be claimed, however, that this view is supported by any extensive body of facts. Since so far as the higher plants are concerned, only fragmentary observations have been recorded on the occurrence and nature of phosphorylated sugars; relatively little is known may be present to act upon such esters. Investigations to be described in this and subsequent communications are directed towards various aspects of this metabolic problem. In the present paper it is proposed to consider a system of enzymes extracted from mature pea seeds which illustrates one type of mechanism by which phosphoric ester are formed in vegetable tissues. Further, the study of this system has disclosed the mechanism by which starch is synthesized in the plant.

scholarly journals Hexapeptide Derivatives of Glycopeptide Antibiotics: Tools for Mechanism of Action Studies

2002 ◽  
Vol 46 (8) ◽  
pp. 2344-2348 ◽  
Author(s):  
Norris E. Allen ◽  
Deborah L. LeTourneau ◽  
Joe N. Hobbs ◽  
Richard C. Thompson
Keyword(s):  
Micrococcus Luteus ◽  
Membrane Vesicles ◽  
Antibacterial Activities ◽  
Mechanisms Of Action ◽  
Side Chain ◽  
Bacterial Membrane ◽  
Glycopeptide Antibiotics ◽  
Bacterial Membranes ◽  
Derivatives Of

ABSTRACT Hexapeptide (des-N-methylleucyl) derivatives of LY264826 were prepared in order to examine further the role of N-substituted hydrophobic side chains in defining the mechanisms of action of semisynthetic glycopeptide antibiotics. The hexapeptide of LY264826 binds to the cell wall intermediate analog l-Lys-d-Ala-d-Ala with a 100-fold lower affinity than LY264826 and inhibits Micrococcus luteus almost 200-fold more poorly than LY264826 does. Alkylation of the 4-epi-vancosamine moiety of the disaccharide significantly enhanced the antibacterial activity of the hexapeptide. Alkylation did not affect the binding affinity for d-alanyl-d-alanine residues; however, it did enhance dimerization 7,000-fold and enhanced binding to bacterial membrane vesicles noticeably compared with the levels of dimerization and binding for the unsubstituted hexapeptide. The findings from this study complement those presented in an earlier report (N. E. Allen, D. L. LeTourneau, and J. N. Hobbs, Jr., J. Antibiot. 50:677-684, 1997) and are consistent with the conclusion that the enhanced antibacterial activities of semisynthetic glycopeptide antibiotics derive from the ability of the hydrophobic side chain to markedly affect both dimerization and binding to bacterial membranes.

Tissue fixation and staining with osmium tetroxide: the role of phenolic compounds.

1978 ◽  
Vol 26 (2) ◽  
pp. 138-140 ◽  
Author(s):  
A J Nielson ◽  
W P Griffith
Keyword(s):  
Phenolic Compounds ◽  
Electron Density ◽  
Normal Tissue ◽  
Osmium Tetroxide ◽  
Direct Interaction ◽  
Plant Tissues ◽  
Tissue Fixation ◽  
Chelate Complexes ◽  
Animal Tissues

It has been postulated that phenol-containing areas of plant and animal tissues were osmiophilic, but proof of direct interaction between osmium tetroxide and phenolic materials, or the nature of such reactions, has been lacking. We find that, under conditions similar to those of normal tissue fixation, osmium tetroxide reacts rapidly with those phenols containing o-dihydroxy groups (including such species found in plant tissues) to give very stable chelate complexes. We conclude that these complexes are responsible for the observed electron-density in phenol-containing areas of tissue treated with osmium tetroxide, so that such phenols are indeed osmiophilic.

scholarly journals Biosynthetic Pathway of Pseudomonas aeruginosa 4-Hydroxy-2-Alkylquinolines

2005 ◽  
Vol 187 (11) ◽  
pp. 3630-3635 ◽  
Author(s):  
Florian Bredenbruch ◽  
Manfred Nimtz ◽  
Victor Wray ◽  
Michael Morr ◽  
Rolf Müller ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biosynthetic Pathway ◽  
Gas Chromatography Mass Spectrometry ◽  
Signal Molecules ◽  
Resonance Spectroscopy ◽  
Bacterial Communication ◽  
Homoserine Lactones ◽  
Feeding Experiments ◽  
Derivatives Of

ABSTRACT The role of intercellular communication in the regulation of bacterial multicellular behavior has received widespread attention, and a variety of signal molecules involved in bacterial communication have been discovered. In addition to the N-acyl-homoserine lactones, 4-hydroxy-2-alkylquinolines (HAQs), including the Pseudomonas quinolone signal, have been shown to function as signal molecules in Pseudomonas aeruginosa. In this study we unraveled the biosynthetic pathway of HAQs using feeding experiments with isotope-labeled precursors and analysis of extracted HAQs by gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy. Our results show that the biosynthesis of various HAQ metabolites is directed via a common metabolic pathway involving a “head-to-head” condensation of anthranilic acid and β-keto fatty acids. Moreover, we provide evidence that the β-keto-(do)decanoic acids, crucial for the biosynthesis of the heptyl and nonyl derivatives of the 4-hydroxyquinolines in P. aeruginosa, are at least in part derived from a common pool of β-hydroxy(do)decanoic acids involved in rhamnolipid biosynthesis.

N6-(Δ2-Isopentenyl)adenosine: Its Conversion to Inosine, Catalyzed By Adenosine Aminohydrolases From Chicken Bone Marrow and Calf Intestinal Mucosa

1971 ◽  
Vol 49 (6) ◽  
pp. 623-630 ◽  
Author(s):  
Ross H. Hall ◽  
Syed N. Alam ◽  
B. D. McLennan ◽  
Claude Terrine ◽  
Jean Guern
Keyword(s):  
Bone Marrow ◽  
Intestinal Mucosa ◽  
Enzyme Preparation ◽  
Biological Behavior ◽  
Side Chain ◽  
Animal Tissues ◽  
Chicken Bone ◽  
Measurable Rate ◽  
Isopentenyl Adenosine ◽  
Derivatives Of

N6-(Δ2-Isopentenyl)adenosine, a component of tRNA, displays biological activity in both plant and animal systems. As part of a study of the biological behavior of this nucleoside, its degradation in animal tissues has been studied. An enzyme that catalyzes conversion of this nucleoside to inosine has been partially purified from chicken bone marrow. The enzyme preparation also catalyzes conversion of adenosine to inosine at about 40 times the rate of conversion of N6-(Δ2-isopentenyl)adenosine. A series of analogues of this nucleoside has been tested as substrates. The Δ3-isomer, n-pentyl, isopentyl, and furfuryl derivatives are readily cleaved. Hydroxylated derivatives of the Δ2-isopentenyl side chain, however, do not serve as substrates. Adenosine aminohydrolase from calf intestinal mucosa also catalyzes conversion of N6-(Δ2-isopentenyl)adenosine to inosine, although in order to obtain a measurable rate, the concentration of enzyme must be about 1000 times that needed to catalyze conversion of adenosine.

The role of silicon in forages: A quantitative X-Ray study

1987 ◽  
Vol 45 ◽  
pp. 416-417
Author(s):  
Janet H. Woodward ◽  
D. E. Akin
Keyword(s):  
Sodium Acetate ◽  
Dry Matter ◽  
Acetate Buffer ◽  
Plant Tissues ◽  
Sodium Acetate Buffer ◽  
X Ray ◽  
Dry Matter Digestibility ◽  
Percent Composition

Silicon (Si) is distributed throughout plant tissues, but its role in forages has not been clarified. Although Si has been suggested as an antiquality factor which limits the digestibility of structural carbohydrates, other research indicates that its presence in plants does not affect digestibility. We employed x-ray microanalysis to evaluate Si as an antiquality factor at specific sites of two cultivars of bermuda grass (Cynodon dactvlon (L.) Pers.). “Coastal” and “Tifton-78” were chosen for this study because previous work in our lab has shown that, although these two grasses are similar ultrastructurally, they differ in in vitro dry matter digestibility and in percent composition of Si.Two millimeter leaf sections of Tifton-7 8 (Tift-7 8) and Coastal (CBG) were incubated for 72 hr in 2.5% (w/v) cellulase in 0.05 M sodium acetate buffer, pH 5.0. For controls, sections were incubated in the sodium acetate buffer or were not treated.

Absolute configuration at C(20) of the derivatives of 21-nor-5α-cholane-20,24-diol

1980 ◽  
Vol 45 (9) ◽  
pp. 2443-2451
Author(s):  
Vladimír Pouzar ◽  
Miroslav Havel
Keyword(s):  
Absolute Configuration ◽  
Side Chain ◽  
Chemical Correlation ◽  
The Absolute ◽  
Derivatives Of

Derivatives of 21-nor-5α-cholane-20,24-diol XI and XIX were prepared by stepwise construction of the side-chain in the position 17β. Their absolute configuration at C(20) was determined on the basis of chemical correlation with the derivatives of 21-nor-5α-cholan-20-ol, XVI and XXIV. The absolute configuration of alcohols XVI and XXIV was determined from the ratio of the yields in which they are formed during the reduction of ketone X and using the benzoate rule. To compounds XI-XVIII the configuration 20R and to compounds XIX-XXVI the configuration 20S has been assigned.

The role of secondary alcoholic groups of D-galacturonan in its degradation with exo-D-galacturonanase

1980 ◽  
Vol 45 (2) ◽  
pp. 427-434 ◽  
Author(s):  
Kveta Heinrichová ◽  
Rudolf Kohn
Keyword(s):  
Acetyl Derivative ◽  
Competitive Inhibitor ◽  
Hydroxyl Groups ◽  
Pectic Acid ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
The Individual ◽  
Degradation Degree ◽  
Derivatives Of

The effect of exo-D-galacturonanase from carrot on O-acetyl derivatives of pectic acid of variousacetylation degree was studied. Substitution of hydroxyl groups at C(2) and C(3) of D-galactopyranuronic acid units influences the initial rate of degradation, degree of degradation and its maximum rate, the differences being found also in the time of limit degradations of the individual O-acetyl derivatives. Value of the apparent Michaelis constant increases with increase of substitution and value of Vmax changes. O-Acetyl derivatives act as a competitive inhibitor of degradation of D-galacturonan. The extent of the inhibition effect depends on the degree of substitution. The only product of enzymic reaction is D-galactopyranuronic acid, what indicates that no degradation of the terminal substituted unit of O-acetyl derivative of pectic acid takes place. Substitution of hydroxyl groups influences the affinity of the enzyme towards the modified substrate. The results let us presume that hydroxyl groups at C(2) and C(3) of galacturonic unit of pectic acid are essential for formation of the enzyme-substrate complex.

scholarly journals Impact of Environmental Factors on Stilbene Biosynthesis

Plants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 90
Author(s):  
Alessio Valletta ◽  
Lorenzo Maria Iozia ◽  
Francesca Leonelli
Keyword(s):  
Environmental Factors ◽  
Biosynthetic Pathway ◽  
In Planta ◽  
Organ Cultures ◽  
Related Plant ◽  
Valuable Compounds ◽  
Stilbene Compounds ◽  
Stilbene Biosynthesis ◽  
Abiotic Environmental Factors

Stilbenes are a small family of polyphenolic secondary metabolites that can be found in several distantly related plant species. These compounds act as phytoalexins, playing a crucial role in plant defense against phytopathogens, as well as being involved in the adaptation of plants to abiotic environmental factors. Among stilbenes, trans-resveratrol is certainly the most popular and extensively studied for its health properties. In recent years, an increasing number of stilbene compounds were subjected to investigations concerning their bioactivity. This review presents the most updated knowledge of the stilbene biosynthetic pathway, also focusing on the role of several environmental factors in eliciting stilbenes biosynthesis. The effects of ultraviolet radiation, visible light, ultrasonication, mechanical stress, salt stress, drought, temperature, ozone, and biotic stress are reviewed in the context of enhancing stilbene biosynthesis, both in planta and in plant cell and organ cultures. This knowledge may shed some light on stilbene biological roles and represents a useful tool to increase the accumulation of these valuable compounds.

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