Biology subjects

Khozin-Goldberg, I.

Publications and source records attributed to Khozin-Goldberg, I..

2 recordsLinked to original sources

bioRxiv2024

Chemoproteomic profiling of serine hydrolases reveals the dynamic role of lipases in Phaeodactylum tricornutum

Phaeodactylum tricornutum is a model oleaginous pennate diatom, widely investigated for the accumulation of triacylglycerols (TAG) in lipid droplets during nitrogen (N) starvation. However, lipid droplet breakdown, TAG catabolism, and remobilization upon N replenishment during growth restoration are less studied. Serine hydrolases (SH) constitute a diverse family encompassing proteases, amidases, esterases, and lipases. In this report, we adopted a chemoproteomic approach called Activity-Based Protein Profiling (ABPP) to explore the repertoire of active serine hydrolases to elucidate the mechanisms of lipid metabolism in P. tricornutum (strain Pt4). A superfamily-wide profile of serine hydrolases revealed a differentially active proteome (activome) during N starvation and after nutrient replenishment. We report 30 active serine hydrolases, which were broadly categorized into metabolic serine hydrolases and serine proteases. Lipases appeared to be the major metabolic linchpins prevalent during lipid remobilization. Global transcriptomics analysis provided a complementary insight into the gene expression level of the detected serine hydrolases. It revealed putative phospholipases as central players in membrane lipid turnover and remodeling involved in cellular lipid homeostasis and TAG accumulation. TAG remobilization and lipid droplet breakdown were impaired in the presence of phenyl mercuric acetate (PMA), whose activity as an SH inhibitor was validated by competitive ABPP. Lipid species profiling corroborated the impairment in TAG degradation and the buildup of structural lipids in the presence of PMA after nutrient replenishment. Collectively, our functional proteome approach, coupled with the transcriptome and lipidome data, provides a comprehensive landscape of bona fide active serine hydrolases, including lipases in this model diatom.

biochemistry↗

bioRxiv2023

Cobalamin production in phototrophic and mixotrophic cultures of nine duckweed species (Lemnaceae)

To feed the rapidly increasing world population, food production will have to double while the amount of water and arable land remain unchanged. Therefore, we must transition to environmentally sustainable, but just as nutritious diets by 2050. This will require drastic reduction in animal-based foods and increasing plant-based foods. Plant- based diets are more sustainable and healthier, with but one exception, plants are low in cobalamin (vitamin B12). Only a few plant and fungi species contain cobalamin, and some of the cobalamin forms present in algae and mushrooms are not available to humans. Recently, the smallest known plant, the edible duckweed Wolffia globosa Mankai, was shown to contain high concentrations of bioavailable cobalamin. We hypothesized that the production of bioavailable cobalamin is not unique to W. globosa Mankai but is common to other duckweed species. We also hypothesized that cobalamin production depends on the conditions under which the duckweed is grown. To test our hypotheses, we cultivated nine duckweed species under mixotrophic and phototrophic conditions, then measured the concentration and identified the bioavailability of cobalamin using biological and analytical methods. Our results showed that all duckweed species tested produce bioavailable cobalamin while pseudocobalamin (the non-available form of cobalamin) was not detected. We also found that mixotrophic conditions enhanced duckweed growth but reduced cobalamin concentrations. Our results establish duckweed species as a novel source of plant-derived bioavailable cobalamin and highlight the effect of growth conditions on production. More research is needed to identify the bacteria responsible for the production of cobalamin in duckweed and to optimize the conditions for cobalamin production.

plant biology↗