Highlights d AdipoAtlas provides a reference lipidome of human white adipose tissue d 1,636 and 737 lipids were identified and quantified by tissue tailored LC-MS lipidomics d AdipoAtlas demonstrates prominent differences between subcutaneous and visceral tissue depots d Obesity leads to the remodeling of sphingo-, ether-, and neutral lipid metabolism

Oxidized phospholipids (oxPLs) have been recently recognized as important mediators of various and often controversial cellular functions and stress responses. Due to the low concentrations in vivo, oxPL detection is mostly performed by targeted mass spectrometry. Although significantly improving the sensitivity, this approach does not provide a comprehensive view on oxPLs required for understanding oxPL functional activities. While capable of providing information on the diversity of oxPLs, the main challenge of untargeted lipidomics is the absence of bioinformatics tools to support high-throughput identification of previously unconsidered, oxidized lipids. Here, we present LPPtiger, an open-source software tool for oxPL identification from data-dependent LC-MS datasets. LPPtiger combines three unique algorithms to predict oxidized lipidome, generate oxPL spectra libraries, and identify oxPLs from tandem MS data using parallel processing and a multi-scoring identification workflow.

In the FeGP cofactor of [Fe]‐hydrogenase, low‐spin FeII is in complex with two CO ligands and a pyridinol derivative; the latter ligates the iron with a 6‐acylmethyl substituent and the pyridinol nitrogen. A guanylylpyridinol derivative, 6‐carboxymethyl‐3,5‐dimethyl‐4‐guanylyl‐2‐pyridinol (3), is produced by the decomposition of the FeGP cofactor under irradiation with UV‐A/blue light and is also postulated to be a precursor of FeGP cofactor biosynthesis. HcgC and HcgB catalyze consecutive biosynthesis steps leading to 3. Here, we report an in vitro biosynthesis assay of the FeGP cofactor using the cell extract of the ΔhcgBΔhcgC strain of Methanococcus maripaludis, which does not biosynthesize 3. We chemically synthesized pyridinol precursors 1 and 2, and detected the production of the FeGP cofactor from 1, 2 and 3. These results indicated that 1, 2 and 3 are the precursors of the FeGP cofactor, and the carboxy group of 3 is converted to the acyl ligand.

Lipids are dynamic constituents of biological systems, rapidly responding to any changes in physiological conditions. Thus, there is a large interest in lipid-derived markers for diagnostic and prognostic applications, especially in translational and systems medicine research. As lipid identification remains a bottleneck of modern untargeted lipidomics, we developed LipidHunter, a new open source software for the high-throughput identification of phospholipids in data acquired by LC-MS and shotgun experiments. LipidHunter resembles a workflow of manual spectra annotation. Lipid identification is based on MS/MS data analysis in accordance with defined fragmentation rules for each phospholipid (PL) class. The software tool matches product and neutral loss signals obtained by collision-induced dissociation to a user-defined white list of fatty acid residues and PL class-specific fragments. The identified signals are tested against elemental composition and bulk identification provided via LIPID MAPS search. Furthermore, LipidHunter provides information-rich tabular and graphical reports allowing to trace back key identification steps and perform data quality control. Thereby, 202 discrete lipid species were identified in lipid extracts from rat primary cardiomyocytes treated with a peroxynitrite donor. Their relative quantification allowed the monitoring of dynamic reconfiguration of the cellular lipidome in response to mild nitroxidative stress. LipidHunter is available free for download at https://bitbucket.org/SysMedOs/lipidhunter .

In the biosynthesis of the iron-guanylylpyridinol (FeGP) cofactor, 6-carboxymethyl-5-methyl-4hydroxy-2-pyridinol ( 1) is 3-methylated to form 2, then 4-guanylylated to form 3, and converted into the full cofactor. HcgA-G proteins catalyze the biosynthetic reactions. Herein, we report the function of two radical S-adenosyl methionine enzymes, HcgA and HcgG, as uncovered by in vitro complementation experiments and the use of purified enzymes. In vitro biosynthesis using the cell extract from the Methanococcus maripaludis ΔhcgA strain was complemented with HcgA or precursors 1, 2 or 3. The results suggested that HcgA catalyzes the biosynthetic reaction that forms 1. We demonstrated the formation of 1 by HcgA using the 3 kDa cell extract filtrate as the substrate. Biosynthesis in the ΔhcgG system was recovered by HcgG but not by 3, which indicated that HcgG catalyzes the reactions after the biosynthesis of 3. The data indicated that HcgG contributes to the formation of CO and completes biosynthesis of the FeGP cofactor.