Biology subjects

Skaugen, M.

Publications and source records attributed to Skaugen, M..

3 recordsLinked to original sources

bioRxiv2019

Seminal quality and global proteomic analysis of spermatozoa from captive Amazon squirrel monkeys (Saimiri collinsi Osgood, 1916) during the dry and rainy seasons

The squirrel monkey (Saimiri collinsi), a Neotropical primate endemic to the Amazon in Brazil, is used as a biological model for reproductive research on the genus Saimiri. Although this animal is known to exhibit reproductive seasonality, nothing is known about the differences in its seminal quality, sperm protein composition, or sperm protein profile between the breeding (dry) and non-breeding (rainy) seasons. Thus, the aims of this study were to evaluate the quality of S. collinsi semen during the dry and rainy seasons and to describe the global sperm proteomics and expression variations in the sperm proteins during the two seasons. Aside from the pH, there was no difference in the seminal quality between the dry and rainy seasons. The study approach based on bottom-up proteomics allowed the identification of 2343 proteins present in the sperm samples throughout these two seasons. Of the 79 proteins that were differentially expressed between the two seasons, 39 proteins that were related to spermatogenesis, sperm motility, capacitation, fecundation, and defense systems against oxidative stress were upregulated in the dry season. Knowledge on the sperm proteins provides crucial information for elucidating the underlying mechanisms associated with sperm functionality. Thus, our results help to advance our understanding of the reproductive physiology of S. collinsi, providing valuable information for the improvement of protocols used in assisted reproduction techniques for the conservation of endangered Saimiri species.

cell biology↗

bioRxiv2019

Proteome analysis of xylose metabolism in Rhodotorula toruloides during lipidproduction

BackgroundRhodotorula toruloides is a promising platform organism for production of lipids from lignocellulosic substrates. Little is known about the metabolic aspects of lipid production from the lignocellolosic sugar xylose by oleaginous yeasts in general and R. toruloides in particular. This study presents the first proteome analysis of the metabolism of R. toruloides during conversion of xylose to lipids.\n\nResultsR. toruloides cultivated on either glucose or xylose was subjected to comparative analysis of its growth dynamics, lipid composition, fatty acid profiles and proteome. The maximum growth and sugar uptake rate of glucose-grown R. toruloides cells were almost twice that of xylose-grown cells. Cultivation on xylose medium resulted in a lower final biomass yield although final cellular lipid content was similar between glucose- and xylose-grown cells. Analysis of lipid classes revealed the presence of monoacylglycerol in the early exponential growth phase as well as a high proportion of free fatty acids. Carbon source-specific changes in lipid profiles were only observed at early exponential growth phase, where C18 fatty acids were more saturated in xylose-grown cells. Proteins involved in sugar transport, initial steps of xylose assimilation and NADPH regeneration were among the proteins whose levels increased the most in xylose-grown cells across all time points. The levels of enzymes involved in the mevalonate pathway, phospholipid biosynthesis and amino acids biosynthesis differed in response to carbon source. In addition, xylose-grown cells contained higher levels of enzymes involved in peroxisomal beta-oxidation and oxidative stress response compared to cells cultivated on glucose.\n\nConclusionsThe results obtained in the present study suggest that sugar import is the limiting step during xylose conversion by R. toruloides into lipids. NADPH appeared to be regenerated primarily through pentose phosphate pathway although it may also involve malic enzyme as well as alcohol and aldehyde dehydrogenases. Increases in enzyme levels of both fatty acid biosynthesis and beta-oxidation in xylose-grown cells was predicted to result in a futile cycle. The results presented here are valuable for the development of lipid production processes employing R. toruloides on xylose-containing substrates.

microbiology↗

bioRxiv2016

Fenton-type chemistry by a copper enzyme: molecular mechanism of polysaccharide oxidative cleavage

The discovery of Lytic Polysaccharide Monooxygenases (LPMOs) has been instrumental for the development of economically sustainable lignocellulose biorefineries. Despite the obvious importance of these exceptionally powerful redox enzymes, their mode of action remains enigmatic and their activity and stability under process conditions are hard to control. By using enzyme assays, mass spectrometry and experiments with labeled oxygen atoms, we show that H2O2, and not O2 as previously thought, is the co-substrate of LPMOs. By controlling H2O2 supply, stable reaction kinetics and high enzymatic rates are achieved, the LPMOs work under anaerobic conditions, and the need for adding stoichiometric amounts of reductants is alleviated. These results offer completely new perspectives regarding the mode of action of these unique mono-copper enzymes, the enzymatic conversion of biomass in Nature, and industrial biorefining.

biochemistry↗