A novel fatty acid-binding protein-like carotenoid-binding protein from the gonad of the New Zealand sea urchin Evechinus chloroticus

Edible Sea urchins Echinus esculentus from Norwegian waters- Effect of season on nutritional quality and chemical contaminants

This study aimed to characterize Echinus esculentus gonads in terms of biometric parameters and nutritional quality at two sites in Mid-Norway at four different seasons. The chemical contamination of the gonads was also investigated for the first time through the evaluation of 28 macro- and trace elements and 32 components from the emerging and persistent group per- and polyfluoroalkyl substances (PFAS). The spawning period was determined in summer, given that the gonad index was the lowest in this season for both sites. Protein concentrations were constant (8%-10%). However, lipid contents (1%-3%) were noticed to be higher in gonads during autumn and winter. The gonads had high contents of PUFA mainly EPA and DHA, followed by SFA, and MUFA year around for both locations. E. esculentus gonads constitute a good source of fatty acids, macro, and trace elements. This species could also be a bioindicator for the monitoring of marine environments.

Microalgal protein AstaP is a potent carotenoid solubilizer and delivery module with a broad carotenoid binding repertoire

Carotenoids are lipophilic substances with many biological functions, from coloration to photoprotection. Being potent antioxidants, carotenoids have multiple biomedical applications, including the treatment of neurodegenerative disorders and retina degeneration. Nevertheless, the delivery of carotenoids is substantially limited by their poor solubility in the aqueous phase. Natural water-soluble carotenoproteins can facilitate this task, necessitating studies on their ability to uptake and deliver carotenoids. One such promising carotenoprotein, AstaP (astaxanthin-binding protein), was recently identified in eukaryotic microalgae, but its structure and functional properties remained largely uncharacterized. By using a correctly folded recombinant protein, here we show that AstaP is an efficient carotenoid solubilizer that can stably bind not only astaxanthin but also zeaxanthin, canthaxanthin, and, to a lesser extent, β-carotene, that is, carotenoids especially valuable to human health. AstaP accepts carotenoids provided as acetone solutions or embedded in membranes, forming carotenoid-protein complexes with an apparent stoichiometry of 1:1. We successfully produced AstaP holoproteins in specific carotenoid-producing strains of Escherichia coli, proving it is amenable to cost-efficient biotechnology processes. Regardless of the carotenoid type, AstaP remains monomeric in both apo- and holoform, while its rather minimalistic mass (~ 20 kDa) makes it an especially attractive antioxidant delivery module. In vitro, AstaP transfers different carotenoids to liposomes and to unrelated proteins from cyanobacteria, which can modulate their photoactivity and/or oligomerization. These findings expand the toolkit of the characterized carotenoid binding proteins and outline the perspective of the use of AstaP as a unique monomeric antioxidant nanocarrier with an extensive carotenoid binding repertoire.

Characterization under quasi-native conditions of the capsanthin/capsorubin synthase from Capsicum annuum L

Chromoplasts are typical plastids of fruits and flowers, deriving from chloroplasts through complex processes of re-organization and recycling. Since this transition leads to the production of reactive species, chromoplasts are characteristic sites for biosynthesis and accumulation of carotenoids and other antioxidants. Here, we have analysed the chromoplast membranes from Capsicum annuum L. fruits, finding a significant expression of the capsanthin/capsorubin synthase. This enzyme was isolated by a very mild procedure allowing its analyses under quasi-native conditions. The isolated complex appeared as a red coloured homo-trimer, suggesting the retention of at least one of the typical carotenoids from C. annuum. Moreover, the protein complex was co-purified with a non-proteinaceous fraction of carotenoid aggregates carrying a high molecular weight and separable only by Size Exclusion Chromatography. This last finding suggested a relationship between the carotenoids synthesis on chromoplast membranes, the presence, and storage of organised carotenoids aggregates typical for chromoplasts. Further MS analyses also provided important hints on the interactome network associated to the capsanthin/capsorubin synthase, confirming its functional relevance during ripening. Results are discussed in the frame of the primary role played by carotenoids in quenching the growing oxidative stress during fruits ripening.

Microsphere packages of carotenoids: intact sea urchin eggs tracked by Raman spectroscopy tools

The native carotenoid content and distribution in intact, freshly released eggs of sea urchin P. lividus are described using resonance Raman spectroscopy; NIR-Raman revealed the additional molecular carotenoid content.