Search results for "Biosynthesi"

Biosynthesis of xanthurenic acid 8-O-beta-D-glucoside in Drosophila. Characterization of the xanthurenic acid:UDP-glucosyltransferase activity.

1990

Xanthurenic acid 8-glucoside is a side metabolite of the tryptophan-xanthommatin pathway in Drosophila. From 3-hydroxykynurenine, two biosynthetic pathways can be envisaged, one via xanthurenic acid, and another via 3-O-glucoside of 3-hydroxykynurenine. In this report evidence is presented to show that the synthesis takes place via xanthurenic acid. (a) We have demonstrated that the Drosophila melanogaster vermilion purple mutant (unable to synthesize 3-hydroxykynurenine) synthesizes xanthurenic acid 8-glucoside when fed with xanthurenic acid; and (b) the activities required for its synthesis via xanthurenic acid have been found (3-hydroxykynurenine transaminase and xanthurenic acid:UDP-glu…

Studies on the biosynthesis of paraherquamide. Construction of the amino acid framework

2001

Abstract It has been previously established in this laboratory that the β-methyl-β-hydroxyproline moiety of the potent anthelmintic agent paraherquamide A, is biosynthetically derived from l -isoleucine. The downstream events from l -Ile to paraherquamide A have now been investigated. The synthesis of [1- 13 C]-labeled l -β-methylproline is described by means of a Hoffman–Loeffler–Freytag reaction sequence from [1- 13 C]- l -Ile. This amino acid is shown to be a direct biosynthetic precursor to paraherquamide A by feeding and incorporation experiments in growing cultures of Penicillium fellutanum . Three tryptophan-containing dipeptides of l -β-methylproline have been constructed: [ 13 C 2 …

Diels-Alderase Catalyzing the Cyclization Step in the Biosynthesis of Spinosyn A

2015

The conversion of putative macrocyclic lactone into the tricyclic compound, as a key step in the biosynthesis of spinosyn A , has been theoretically investigated using DFT methods. The relatively low activation free energy computed for the cyclization process of the actual macrocyclic lactone (21.0 kcal/mol) furnishes a rationalization for a spontaneous ( i.e. nonenzymatically catalyzed) cyclization process in the biosynthesis of spinosyn A . A geometric analysis of putative macrocyclic lactone indicates that a slight strain on the lactone at the active site of the SpnF gene could decrease the activation free energy to ca . 16 kcal/mol. This nonspecific participation of the enzyme, which ac…

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…