Search results for "Biosynthesis"

Erratum to “3D-Structure and function of strictosidine synthase – The key enzyme of monoterpenoid indole alkaloid biosynthesis” [Plant Physiol. Bioch…

2008

Revisiting delta-6 desaturase regulation by C18 unsaturated fatty acids, depending on the nutritional status.

2009

Dietary polyunsaturated fatty acids (PUFA) play a key role in regulating delta-6 desaturase (D6D), the key enzyme for long-chain PUFA biosynthesis. Nevertheless, the extent of their effects on this enzyme remains controversial and difficult to assess. It has been generally admitted that C18 unsaturated fatty acids (UFAs) regulate negatively delta-6 desaturase (D6D). This inhibition has been evidenced in regard to a high glucose/fat free (HG/FF) diet used in reference. However, several nutritional investigations did not evidence any inhibition of desaturases when feeding fatty acids. Because the choice of the basal diet appeared to be of primary importance in such experiments, our goal was t…

Herbicidally Active Derivatives of Aminomethylenebis-Phosphonic Acid-Mode of Action and Structure - Activity Relationship

1996

Abstract: (N-pyridylamino)methylenebisphosphonates exhibit strong herbicidal activity which may be reversed by supplementation of the growth media with aromatic amino acids. They appeare to be the inhibitors of aromatic amino acids biosynthesis acting as inhibitors of DAHP synthase the first enzyme of shikimate pathway. Over 40 analogues of these acids were synthesized in order to determine the structure-activity relationship.

Biological Activities of Natural Sesquiterpene Lactones and the Effect of Synthetic Sesquiterpene Derivatives on Insect Juvenile Hormone Biosynthesis

1998

Three natural sesquiterpene lactones have been assayed for their biological activity on locust (Locusta migratoria) nymphs. Since results obtained in vivo pointed to disruptions on juvenile hormone (JH)-regulated physiology, we tested the sesquiterpene lactones and a family of synthetic sesquiterpene derivatives for their ability to disturb the rate of JH biosynthesis by locust corpora allata (CA) in vitro. All the active compounds in vitro share a basic sesquiterpene double-ring structure as well as substituents with different chemical complexities. Compounds that shared an eudesmane base with different oxidation states on C3 and C12 carbon atoms were tested as JH biosynthesis inhibitors. …

Mode of action of herbicidal derivatives of aminomethylenebisphosphonic acid. Part II. Reversal of herbicidal action by aromatic amino acids

1997

The herbicidal action of N-pyridylaminomethylenebisphosphonic acids is accompanied by an impairment of anthocyanin biosynthesis. This suggests that they might act as inhibitors of some steps in aromatic amino acid biosynthesis. Herbicidal effects were reversed by aromatic amino acids using both bacterial and plant models, a finding that strongly supports this hypothesis. Structural features of these compounds suggest the sixth enzyme in the shikimate pathway 5-enol-pyruvoylshikimate-3-phosphate (EPSP) synthase as a possible target, since a strong structural similarity exists between aminomethylenebisphosphonic acid and an inhibitor of EPSP synthase, the herbicide glyphosate. This is, howeve…

Addition of reducing agent dithiothreitol improves 4-decanolide synthesis by the genus Sporidiobolus.

2000

Two species of the genus Sporidiobolus, S. johnsonii and S. ruinenii, were used to study the effect of the reducing agent, dithiothreitol (DTT), on 4-decanolide production using ricinoleic acid as the substrate. The results indicate that the addition of DTT into the cultures significantly enhanced 4-decanolide biosynthesis by the two species.

Enzymatic Biosynthesis of Vomilenine, a Key Intermediate of the Ajmaline Pathway, Catalyzed by a Novel Cytochrome P 450-Dependent Enzyme from Plant C…

1995

Abstract Microsomal preparations from Rauwolfia serpentina Benth. cell suspension cultures cata­lyze a key step in the biosynthesis of ajmaline -the enzymatic hydroxylation of the indole alkaloid vinorine at the allylic C-21 resulting in vomilenine. Vomilenine is an important branch-point intermediate, leading not only to ajmaline but also to several side reactions of the biosynthetic pathway to ajmaline. The investigation of the taxonomical distribution of the enzyme indicated that vinorine hydroxylase is exclusively present in ajmaline-producing plant cells. The novel enzyme is strictly dependent on NADPH2 and O2 and can be inhibited by typical cytochrome P450 inhibitors such as cytochrom…

Enzymatic biosynthesis of raumacline

1995

Abstract The indole alkaloid, raumacline, is biosynthesized from ajmaline, when the latter was fed to cell suspensions of Rauwolfia serpentina . Formation in catalysed by two enzymes, a cell wall-bound peroxidase followed by a NADPH 2 -dependent reductase. The first enzyme cleaves ajmaline oxidatively leading to a C-21 epimeric mixture of 21-hydroxyraumacline, a novel alkaloid, which, in turn, is reduced under formation of raumacline. The peroxidase reaction is not specific for Rauwolfia cells whereas the reductase is present exclusively in Rauwolfia cell suspensions. The reductase has been purified to homogeneity. The enzyme is highly substrate specific, only accepting 21-hydroxyraumacline…

Mechanism of the Antiretroviral Effect of dsRNA

1994

The development of AIDS seems to be linked to an impairment of processes which are induced or activated by double-stranded RNA (dsRNA), such as the biosynthesis of interferon (IFN), production of 2′,5′-oligoadenylate (2-5A), ribonuclease L (RNase L) activity and different cell-mediated immune functions. A restriction of available bioactive dsRNA (or of dsRNA-dependent enzymes) may play an important role in the disease progression. The results summarized in this review show that defects in dsRNA-dependent pathways exhibited by AIDS patients can be reversed, at least in part, by exogenously supplied dsRNA.

Determination of the stability of protein pools from the cell wall of fungi.

2002

Stability of the protein populations present in the cell wall of three ascomycetous fungi Candida albicans, Saccharomyces cerevisiae and Yarrowia lipolytica was investigated. Cell wall proteins were either labeled with biotin or radiolabeled with amino acids, and chased for a period of time representing several generations. Proteins linked by non-covalent or covalent bonds were separated and their turnover was analyzed. No significant turnover took place during the chase period, and in fact radioactive proteins were accumulated in the wall during the period possibly by transfer through the secretory pathway. This transfer did not involve de novo protein synthesis; it was inhibited by azide,…