The effect of selenium enrichment on baker's yeast proteome

Abstract

The use of regular yeast (RY) and selenium-enriched yeast (SEY) as dietary supplement is of interest because the Nutritional Prevention of Cancer (NPC) trial revealed that SEY but not RY decreased the incidence of prostate cancer (PC). Using two-dimensional difference in gel electrophoresis (2D-DIGE) -tandem mass spectrometry (MS/MS) approach, we performed proteomic analysis of RY and SEY to identify proteins that are differentially expressed as a result of selenium enrichment. 2D-DIGE revealed 96 candidate protein spots that were differentially expressed (p≤0.05) between SEY and RY. The 96 spots were selected, sequenced by LC/MS/MS and 37 proteins were unequivocally identified. The 37 identified proteins were verified with ProteinProphet software and mapped to existing Gene Ontology categories. Furthermore, the expression profile of 5 of the proteins with validated or putative roles in the carcinogenesis process, and for which antibodies against human forms of the proteins are available commercially were verified by western analysis. This study provides evidence for the first time that SEY contains higher levels of Pyruvate Kinase, HSP70, and Elongation factor 2 and lower levels of Eukaryotic Translation Initiation Factor 5A-2 and Triosephosphate Isomerase than those found in RY.

Biochemical Comparison of Commercial Selenium Yeast Preparations

“…SeMet containing peptides were detected in Adh1 from products 2, 3 and SELM-1, but the overall abundance of the Adh1 protein was significantly higher in product 3 compared to SELM-1. Proteins with Se modifications including Ahp1, Bmh1, Eno1, Eno2, Sip18 and Mmf1 were also identified in previous studies on Se yeast [16,25,50,51] thus corroborating the results presented in Table 1. Three different isoforms of glyceraldehyde-3-phosphate dehydrogenase (Tdh1, Tdh2 and Tdh3) were also identified.…”

“…For example, Tdh3 was identified in two products but at opposing abundance levels. As glyceraldehyde-3-phosphate dehydrogenase is involved in oxidation-reduction pathways, differential expression may be due to stress imposed by Se salt addition during fermentation, thus highlighting that a range of divergent manufacturing methods may used to generate Seenriched yeast products [16,39] resulting in inherent differences between preparations. It is clear that bioavailability of SeMet will be dependent not only on the abundance of a particular Se-containing protein but also on the position of SeMet residues within the protein; therefore, consideration must be given to the strain-specific deposition of Se into individual protein and peptide-containing fractions [55].…”

“…It is also worth noting that the water extraction used in this study is vastly different from volatile conditions encountered in the GI tract where conditions will solubilise some proteins and destabilise others [59]. Therefore, the extent to which the active forms of yeast proteins identified can be transported intact across the intestinal barrier, and the biological effect of such proteins or corresponding peptides must be determined in preclinical animal models before any definitive conclusions can be made on potential beneficial health effects [16]. Nevertheless, knowledge of a group of proteins that respond to Se supplementation will be useful in the assessment of a particular metabolic status [60].…”

“…LC-MS/MS was used to identify and quantify individual proteins present in the soluble extracts. Protein identities were validated using UniProt, and Gene Ontology classification was performed to define the potential biological role of the identified proteins and their relevance to animal health [16]. Characterisation of Se yeast in this way provides a unique fingerprint of origin and accounts for fate of Se during the production process, which is paramount importance for regulatory and safety agencies [17].…”

Evaluation of sodium selenite effects on the potential probiotic Saccharomyces cerevisiae UFMG A-905: A physiological and proteomic analysis

“…Generally, this enzyme directs DHAP towards GAP, thus improving the flow through the glycolytic pathway and producing more ATP. El-Bayoumy et al (2012) have reported that the expression of this enzyme is repressed by Se; although the mechanism involved in this decrease is still unclear, the authors suggested that Se might disrupt glycolysis. It is reasonable to conclude that TPI1 down-regulation is in some way linked to the use of DHAP for glycerol biosynthesis instead of shifting it towards glycolysis.…”