1,721,007 research outputs found
Biosynthetic Pathways in Marine Invertebrates as Untapped Resource of Biotechnological Applications
No full textMarineinvertebrates have been emerging as a very promising source of both natural products and enzymatic activities. In this contribution, we have tried to provide a general overview of the present knowledge of the enzymatic transformations and biosynthetic pathways in marine molluscs, suggesting that marine enzymes have great, yet unexplored diversity in both mechanism and structure. We hope that the extraordinary mechanism and catalytic reactivity discussed throughout the manuscript may serve as an inspiration in searching for novel biocatalytic properties
Polyketide origin of 3-alkylpyridines in the marine mollusc Haminoea orbignyana
No full textThe paper reports the biosynthesis of the main alkylpyridine alkaloids, haminol-1 (1) and -2 (2), in the Mediterranean
mollusc Haminoea orbignyana. Experiments were carried out by in vivo incorporation of [1,2-13C2 acetate]. Data give full account
for a polyketide origin of haminols in the Mediterranean molluscs, showing the biosynthesis of these 3-alkylpyridine alkaloids by
elongation with acetate of a starter unit of nicotinic acid
Shaping the Polypropionate Biosynthesis in the solar powered mollusc Elysia viridis
No full textPolypropionates that incorporate pyrones are a family of polyketides
featuring the chemistry of a few marine molluscs capable
of phototrophic CO2 fixation as a result of storing viable symbiotic
chloroplasts in their bodies. The role and origin of these molecules
is poorly investigated, although the unusual biological
ACHTUNGTRENUNGactivities and chemistry of these natural products have recently
received renewed interest. Here, we report the results of in vivo
studies on production of g-pyrone-containing polypropionates in
the Mediterranean mollusc Elysia viridis. Biosynthesis of the metabolites
in the sacoglossan is shown to proceed through condensation
of eight intact C3 units by polyketide synthase assembly.
LC–MS and NMR spectroscopic studies demonstrate that the
process involves a pyrone tetraene (10) as key intermediate,
whereas the levels of the final polypropionates (6, 7 and 9) are
related to each other and show a significant dependence upon light conditions
Lipase-mediated production of defensive toxins in the marine mollusc Oxynoe olivacea
No full textMetabolites related to caulerpenyne (1), a toxic sesquiterpene featured by two enol-acetate residues, play a major
role in the chemical defence of both algae of the genus Caulerpa and a few molluscs of the order Sacoglossa. Here
we report the direct evidence that cell-free preparations of Oxynoe olivacea, a Mediterranean sacoglossan, transform
efficiently the algal metabolite 1 to oxytoxin-2 (3), the main defensive metabolite of the mollusc. The process
implies two distinct hydrolytic activities, here named LIP-1 and LIP-2, able to operate either hydrolysis of the acetyl
residue at C-1 or concerted elimination of the acetyl groups at C-4 and C-13. Incubation experiments with tissue
homogenates of O. olivacea or with commercially available lipases suggest a two-step mechanism that involves,
in vitro, an unstable metabolite characterized as preoxytoxin-2 (4). The course of the entire process can be easily
monitored by reverse phase HPLC/ESI-MS, as well as by NMR measurements, which provides direct evidence of
the enzymatic mechanism leading to the formation of this last compound (4). In agreement with the literature, both
fresh and frozen tissues of Mediterranean Caulerpa prolifera also have the capability to transform 1 into aldehydic
derivatives, namely oxytoxin-1 (2) and oxytoxin-2 (3), through hydrolysis of the acetyl groups. However, differently
from experiments with mollusc homogenates, the conversion is not complete and caulerpenyne (1) can be detected in
the algal suspension for a few hours. HPLC/ESI-MS monitoring of this transformation suggests that the hydrolytic
route involves different activities in the mollusc and seaweed
Placidenes C-F, novel γ-pyrone propionates from the Mediterranean Sacoglossan Placida dendritica
No full textFour new R-pyrone-containing propionates (5-8) and an unprecedented hydroperoxide 9 have been isolated
from the mantle extract of Placida dendritica, a Mediterranean sacoglossan that lives upon the green
alga Bryopsis plumosa. The new metabolites co-occur with the related compounds 1-4, which have been
described in previous studies of the mollusc. The presence of 9 opens intriguing perspectives on the
ecological role of placidenes. This paper reports the isolation and structural elucidation of the new
compounds 5-9
Biosynthesis in Opisthobranch Molluscs: general outline in the light of recent use of stable isotopes
No full textThe use of stable isotopes has been recently introduced in the biosynthetic studies of metabolites produced by opisthobranch molluscs. This methodology offers numerous advantages since it avoids the complex and tedious manipulations of potentially dangerous radioactive compounds and gives unequivocal evidence for the incorporation. In these studies, high field NMR spectroscopy is a particularly useful tool to localize the labeled atoms in the molecule. This chapter updates the biosynthetic studies on opisthobranch molluscs with particular attention to the recent experiments with precursors labeled with stable isotopes. Opisthobranchs are able to biosynthesize de novo a wide array of chemical skeletons including polyketides, polypropionates, acetogenins, and terpenoids. The studies regarding this latter class is proposed in the light of the recent debate about classical and independent mevalonate pathway
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