Biosynthesis of α-linolenic acid by desaturation of oleic and linoleic acids in several organs of higher and lower plants and in algae

The biosynthesis of α-linolenic acid by successive desaturations of oleic and linoleic acids has been shown to occur in the leaves, roots and seeds of many higher plants. The age and the physiological state of the plant organs are extremely important. This route occurs also in several lower plants including algae. It is concluded that the desaturation pathway is the major route for the biosynthesis of α-linolenic acid in plants.     

Investigation of algae and yeast for α-tocopherol and α-tocopherolquinone content

Five species of yeast and nine species of algae were analyzed for their content of α-tocopherol and α-tocopherolquinone. No α-tocopherol or α-tocopherolquinone was found in any of the yeasts examined. However, several of the algae contained α-tocopherol and α-tocopherolquinone. A brine water alga, Stichococcus bacillaris, contained the largest amount of α-tocopherol (134·2 μg/g dry weight) and a brown marine alga, Macrocystis integrifolia, contained the largest amount of α-tocopherolquinone (11·9 μg/g dry weight). None of these organisms would appear to be as suitable as Euglena gracilis for studies of the biosynthesis of α-tocopherol and α-tocopherolquinone.     

Biosynthesis of peptides containing α-aminoadipic acid and cysteine in extracts of a Cephalosporium sp

1. Three intracellular peptides found in small amount in a Cephalosporium sp. were rapidly labelled when dl-[(14)C]valine was added to a shaken suspension of the organism. More (14)C was incorporated into peptide P3, delta-(l-alpha-aminoadipyl)-l-cysteinyl-d-valine, than into peptide P2 (containing alpha-aminoadipic acid, cysteine, valine and glycine) or peptide P1 (containing beta-hydroxyvaline in place of the valine in peptide P2). 2. Peptides P3 and P2, but not peptide P1 were formed in a broken-cell system from the Cephalosporium sp. in the presence of delta-(l-alpha-aminoadipyl)-l-cysteine and dl-[(14)C]valine. No synthesis was observed in the presence of delta-(d-alpha-aminoadipyl)-l-cysteine or of dl-alpha-amino[(14)C]adipic acid and l-cysteinyl-l-valine or l-cysteinyl-d-valine. 3. The biosynthesis of these peptides was catalysed by the particulate fraction of the broken-cell system, whereas that of glutathione was catalysed by the supernatant fraction. 4. These results are discussed in relation to penicillin N and cephalosporin C biosynthesis.     

Biosynthesis of mimosine: Incorporation of serine and of α-aminoadipic acid

Serine serves as a precursor of the alanyl side-chain of mimosine. Activity from α-aminoadipic acid is incorporated into the γ-pyridone nucleus. Pipecolic acid and 5-hydroxypipecolic acid occur in Mimosa pudica.     

Recent progress of algae and blue–green algae-assisted synthesis of gold nanoparticles for various applications

Bioprocess and Biosystems Engineering - The hazardous effects of current nanoparticle synthesis methods have steered researchers to focus on the development of newer environmentally friendly and...     

Biosynthesis,cDNA and amino acid sequences of a precursor of conglutin δ, a sulphur-rich protein from Lupinus angustifolius

The biosynthesis of conglutin has been studied in developing cotyledons of Lupinus angustifolius L. Precursors of conglutin formed the major sink for [³⁵S]-cysteine incorporated by developing lupin cotyledons, and these precursors were rapidly sequestered into the endoplasmic reticulum. The sequence of a cDNA clone coding for one such precursor of conglutin was determined. The structure of the precursor polypeptide for conglutin predicted from the cDNA sequence contained an N-terminal leader peptide of 22 amino acids directly preceding a subunit polypeptide of M _r 4520, together with a linking region of 13 amino acids and a subunit polypeptide of M _r 9558 at the C-terminus. The amino acid sequence predicted from the cDNA sequence showed minor variations from that established by sequencing of the protein purified from mature dried seeds (Lilley and Inglis, 1986). These were consistent with the existence of a multi-gene family coding for conglutin . Comparison of the sequences of conglutin with those of other 2S storage proteins showed that the cysteines involved in internal disulphide bridges between the mature subunits of conglutin , were maintained throughout this family of proteins but that little else was conserved either at the protein or DNA level.     

Is there an osmotic regulatory mechanism in algae and higher plants?

Under water-stress conditions the amounts of various polyols and also of the imino acid proline are found to increase significantly in different algae and higher plants. These substances have been interpreted until now to act osmotically by increasing the concentration in the cell, thus causing water reflux and balancing osmotic pressure difference from outside the cell to inside.A new concept is described, which proposes that the regulatory function of these accumulating substances is conducted by two mechanisms quite different from osmotic regulation. It is assumed that these regulatory pathways are connected with the hydrophobic groups of biopolymers in the cell cytoplasm. (1) Polyols can replace water molecules by means of their water like OH-groups and thus participate in the hydrophobically enforced water structure. (2) Proline is postulated to associate via its hydrophobic phot with hydrophobic side chains, thereby converting them into hydrophilic groups by exposure the carboxylic and imino group versus water molecules. The advantage is due to the fact that water associated with hydrophilic groups is bound via hydrogen bonding forces, in contrary to hydrophobic groups. In addition, the number of water molecules adjoining hydrophilic groups is far less than those involved with hydrophobic residues. By means of these two alternative mechanisms complete hydration of the biopolymers is maintained, even with a reduced number of available water molecules.     

Biosynthesis of D-glucaric acid in mammals: a free-radical mechanism?

In the presence of iron salts and hydrogen peroxide, D-glucuronic acid was converted into D-glucaric acid. The reaction was strongly inhibited by free-radical scavengers and is ascribed to the action of the hydroxyl radical. The formation of D-glucarate was dependent upon pH and occurred in the presence of some iron-complexing agents. The first product of oxidation was a lactone that was a strong inhibitor of beta-D-glucuronidase and assumed to be D-glucaro-1,5-lactone. Microsomal preparations in the presence of NADPH also produced D-glucarate from D-glucuronic acid, presumably due to formation of hydrogen peroxide, and the product was an inhibitor of beta-D-glucuronidase. Superoxide did not produce D-glucarate from D-glucuronate. The cytochrome P450 system is more likely than \"glucuronolactone dehydrogenase\" to be responsible for the production of D-glucaric acid in vivo.     

Origin of sucrose metabolism in higher plants: when,how and why?

Since the discovery of sucrose biosynthesis, considerable advances have been made in understanding its regulation and crucial role in the functional biology of plants. However, important aspects of this metabolism are still an enigma. Studies in cyanobacteria and the publication of the sequences of several complete genomes have recently significantly increased our knowledge of the structures of proteins involved in sucrose metabolism and given us new insights into their origin and further evolution.     

Relationship between transport and metabolism of α-naphthaleneacetic acid, β-naphthaleneacetic acid and α-decalylacetic acid in segments of Coleus

Summary Transportand metabolism of -naphthaleneacetic acid -naphthaleneacetic acid, and -decalylacetic acid, all labelled with ¹⁴C in the carboxyl, group, were studied. Only -naphthaleneacetic acid is transported in a polar way. Most of the radioactivity in the tissue is in a low molecular form, either free or as immobilization products. The immobilization of -naphthaleneacetic acid is similar to that of -naphthaleneacetic acid. Immobilization of -decalylacetic acid is typically different. Bioassays showed -naphthaleneacetic acid as the sole biologically active component. It is concluded that stereo requirements necessary for biological activity are also required for polar auxin transport. It is further concluded that the observed specificity of the transport system is not related to the formation of immobilization products.     

Biosynthesis and disposition of γ-guanidinobutyric acid in mammalian tissues

Transamidinase of kidney and pancreas was shown to catalyze the formation of γ-guanidinobutyric acid from γ-aminobutyric acid and arginine. The enzyme was also shown to be present in brain. Glycine was about ten times more active than γ-aminobutyric acid. A number of amino acids were tested for activity with purified hog kidney transamidinase. In addition to γ-aminobutyric acid, β-alanine, δ-aminovaleric, and lysine all had demonstrable activity.γ-Guanidinobutyric acid was found in all tissues of the rat. Following the intraperitoneal injection of γ-guanidinobutyric acid, no increase was observed in the brain concentration indicating that at least in brain, γ-guanidinobutyric acid arises mainly through synthesis and not as a result of dietary intake.     

Effects of the potential allelochemical α-asarone on growth,physiology and ultrastructure of two unicellular green algae

The effects of the natural phenylpropanoid -asarone on growth pattern, photosynthesis, respiration and cell structure of two microalgae have been investigated. In cultures ofAnkistrodesmus braunii -asarone decreases in the medium and induces a lag in growth. Both phenomena were dependent on the number of cells inoculated. By contrast, in cultures ofSelenastrum capricornutum a constant decrease of the growth rate at all inocula was observed and only a slight decrease of -asarone in the medium occurred. In both algae -asarone caused an initial inhibition of photosynthesis, followed by a resumption of control values. The respiratory rate ofA. braunii was not significantly affected by -asarone, whereas inS. capricornutum respiration lowered to 60% of the control in the first 48 h and subsequently rose to values exceeding the controls by 20%. Ultrastructural observations carried out 24 and 72 h after the addition of -asarone showed modifications of cell wall inA. braunii, an increase in the number of mithocondrial profiles per cell section inS. capricornutum, and an accumulation of electron-dense deposits in the vacuoles of both algae.Author for correspondence     

Endoplasmic reticulum and microtubule formation in dividing cells of higher plants—a postulate

Summary In spite of the increase in volume of literature on the fine structure of events during division in cells of higher plants, the presence of any kind of a centriole or centriole-like structure has not been demonstrated. However, recent studies have contained data which point to a relationship between membranous elements (usually smooth endoplasmic reticulum) and spindle microtubules in polar regions of dividing cells. These previously reported data, together with data in this present work, are combined into the formulation of an hypothesis relative to the possible role of membranes, particularly smooth endoplasmic reticulum, as cell centers in the assembly and disposition of spindle microtubules in dividing cells of higher plants.This work was supported in part by the Training Grant DS00184 from the National Institutes of Health.     

Biosynthesis and cell-wall deposition of a pectin–xyloglucan complex in pea

Golgi-enriched enzyme preparations prepared from etiolated pea epicotyls incorporated [U–¹⁴C]galactose from UDP-[U–¹⁴C]galactose into the 1,4--galactan sidechains of a pectin–xyloglucan complex. This complex could bind to paper and was degraded both by pectin-degrading enzymes and by a xyloglucan-specific endoglucanase. Gel permeation chromatography was used to assess the molecular size of the complex and of enzymically-degraded, galactan-containing fragments of it. Etiolated pea stems were labelled with [U–¹⁴C]sucrose for 1 h, and the newly-synthesised cell wall polysaccharides were extracted with EDTA or NaOH and fractionated by ion-exchange chromatography. The NaOH-extracted, acidic radioactive polysaccharides obtained in this way were also degraded both by pectin-degrading enzymes and by xyloglucan-specific endoglucanase. Analysis of the radioactive sugar composition indicated that neutral sugars characteristic of both pectin and xyloglucan were present. Analysis of the total non-radioactive, neutral sugar composition of the NaOH-extracted, acidic cell-wall polysaccharides indicated that pectin–xyloglucan complexes were a general feature of the cell wall in this tissue     

Studies on carbohydrate-metabolizing enzymes. The hydrolysis of α-glucosides, including nigerose, by extracts of alfalfa and other higher plants

1. Enzyme preparations from 11 plant sources, from yeast and from the protozoan Tetrahymena pyriformis show nigerase activity, which, in most preparations, was 70–90% of that towards maltose. 2. These enzyme preparations also hydrolysed isomaltose, but there was a wide variation in relative maltase to isomaltase activity. 3. The maltase and nigerase activities of alfalfa and tomato preparations could not be differentiated by heat inactivation or inhibitor methods. However, with turanose used as a competitive inhibitor, evidence suggesting that maltose and nigerose are hydrolysed at different catalytically active sites in the alfalfa preparation was obtained. 4. It is probable that the alfalfa α-glucosidase exists as a mixture of isoenzymes.     

Chloroplast sulfate transport in green algae – genes,proteins and effects

This review summarizes evidence at the molecular genetic, protein and regulatory levels concerning the existence and function of a putative ABC-type chloroplast envelope-localized sulfate transporter in the model unicellular green alga Chlamydomonas reinhardtii. From the four nuclear genes encoding this sulfate permease holocomplex, two are coding for chloroplast envelope-targeted transmembrane proteins (SulP and SulP2), a chloroplast stroma-targeted ATP-binding protein (Sabc) and a substrate (sulfate)-binding protein (Sbp) that is localized on the cytosolic side of the chloroplast envelope. The sulfate permease holocomplex is postulated to consist of a SulP–SulP2 chloroplast envelope transmembrane heterodimer, flanked by the Sabc and the Sbp proteins on the stroma side and the cytosolic side of the inner envelope, respectively. The mature SulP and SulP2 proteins contain seven transmembrane domains and one or two large hydrophilic loops, which are oriented toward the cytosol. The corresponding prokaryotic-origin genes (SulP and SulP2) probably migrated from the chloroplast to the nuclear genome during the evolution of Chlamydomonas reinhardtii. These genes, or any of its homologues, have not been retained in vascular plants, e.g. Arabidopsis thaliana, although they are encountered in the chloroplast genome of a liverwort (Marchantia polymorpha). The function of the SulP protein was probed in antisense transformants of C. reinhardtii having lower expression levels of the SulP gene. Results showed that cellular sulfate uptake capacity was lowered as a consequence of attenuated SulP gene expression in the cell, directly affecting rates of de novo protein biosynthesis in the chloroplast. The antisense transformants exhibited phenotypes of sulfate-deprived cells, displaying slow rates of light-saturated oxygen evolution, low levels of Rubisco in the chloroplast and low steady-state levels of the Photosystem II D1 reaction center protein. The role of the chloroplast sulfate transport in the uptake and assimilation of sulfate in Chlamydomonas reinhardtii is discussed along with its impact on the repair of Photosystem II from a frequently occurring photo-oxidative damage and H₂-evolution related metabolism in this green alga.     

Biosynthesis and degradation of α-tomatine in developing tomato fruits

Fruits of tomato incorporated [2-¹⁴C]mevalonic acid lactone into the steroidal glycoalkaloid α-tomatine. Young fruits showed the greatest alkaloid-synthesizing ability but this decreased as the fruits developed. Analysis of sap exuded from fruit stalks and also application of[4-¹⁴C]cholesterol to leaves confirmed that tomatine is not transported into fruits from vegetative organs. Accumulation of this alkaloid in fruits thus appears entirely due to synthesis. Excised fruits of all developmental stages degraded injected [¹⁴C]tomatine and rates were directly related to fruit age. The pattern of accumulation/decline in fruit tomatine may be explicable on the basis of changing capacity for synthesis/degradation during development. Label from injected [¹⁴C]tomatine was present mainly in chlorophylls and carotenoids where it increased with time as that in tomatine decreased. The significance of the relationship between tomatine disappearance and carotenoid development is briefly discussed. The aglycone tomatidine was not detected in green fruits but a Δ¹⁶-5α-pregnenolone-like compound was.