APA variations revealed that the synthesis of AP was repressed over a PO43− threshold between 0.4 and 1 μM. As
lower PO43− concentrations are regularly observed during A. catenella blooms in Thau lagoon, a significant portion of P uptake by A. catenella cells in the field may come from organic compounds. “
“Carbonic anhydrase (CA) is a ubiquitous metalloenzyme responsible for accelerating the interconversion of CO2 and bicarbonate. Although CAs are involved in a broad range of biochemical processes involving carboxylation or decarboxylation reactions, they are of special interest due to their role in photosynthetic CO2 assimilation in marine phytoplankton, especially under low-CO2 conditions. Several phylogenetically independent classes of CAs have been identified in a variety of marine phytoplankton. Daporinad TWCA1, first discovered in Thalassiosira weissflogii (Grunow) G. Fryxell & Hasle, is the founding member of the δ-class of CAs; these appear to be extracellular enzymes, but are still relatively poorly characterized. MAPK Inhibitor Library To date, it has remained uncertain whether TWCA1 possesses true CA activity due to the difficulty in producing a functional protein in a heterologous expression system. Herein we describe the fusion of a full-length open reading frame of TWCA1 to the coding sequence of a self-splicing
intein in a pTWIN2 expression vector that has allowed successful production of a functional enzyme in Escherichia coli. Assay of the recombinant protein shows that TWCA1 is a catalytically active δ-CA possessing both CO2 hydration and esterase activity. “
“Dinoflagellates are prolific producers of polyketide this website secondary metabolites. Dinoflagellate polyketide synthases (PKSs) have sequence similarity to Type I PKSs, megasynthases that encode all catalytic domains on a single polypeptide. However, in dinoflagellate PKSs identified to date, each catalytic domain resides on a separate transcript, suggesting multiprotein complexes similar to Type II PKSs. Here, we provide evidence through coimmunoprecipitation
that single-domain ketosynthase and ketoreductase proteins interact, suggesting a predicted multiprotein complex. In Karenia brevis (C.C. Davis) Gert Hansen & Ø. Moestrup, previously observed chloroplast localization of PKSs suggested that brevetoxin biosynthesis may take place in the chloroplast. Here, we report that PKSs are present in both cytosol and chloroplast. Furthermore, brevetoxin is not present in isolated chloroplasts, raising the question of what chloroplast-localized PKS enzymes might be doing. Antibodies to K. brevis PKSs recognize cytosolic and chloroplast proteins in Ostreopsis cf. ovata Fukuyo, and Coolia monotis Meunier, which produce different suites of polyketide toxins, suggesting that these PKSs may share common pathways.