Effect of soy peptide on brewing beer

Wan

et al. 2014

Int J of Food Sci Tech

Soy protein isolate was hydrolysed with Alcalase, Papain, Flavorzyme and Protemax, respectively, and further fractioned by ultrafiltration. The resulting soy protein hydrolysates (SPH) and their ultrafiltration fractions were used to examine their effects on the growth and fermentation performances of brewer's yeast. Results showed that degree of hydrolysis, molecular weight distribution and amino acid composition of SPH significantly affected the growth, viability and fermentation performance of brewer's yeast. The SPH prepared from different proteolytic enzymes exhibited distinct growth-and fermentation-promoting activity for brewer's yeast. The SPH treated with Protemax for 9 h and with the molecular weight below 3 kDa showed the highest growth-promoting activity and induced more rapidly reducing sugar consumption and higher ethanol production. The relatively lower molecular weight and the hydrophilic and electropositive amino acid residues (Lys, His, Arg and Ile) in SPH might be responsible for its functionality, promoting the growth and fermentation of brewer's yeast.

Section: Resultsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 98%

Effects of soy protein hydrolysates on the growth and fermentation performances of brewer's yeast

Wan

et al. 2014

Int J of Food Sci Tech

“…For the yeast S. cerevisiae , Ptr2p is the major transporter involved in the uptake of di/tripeptides17181920. Because the uptake of amino acids in the peptide form is much faster than in the amino-acid form, peptide-based media can improve the growth of yeasts621. Although Ptr2p is an important protein for the fermentation industry, there is little information on the substrate preferences of Ptr2p22.…”

mentioning

confidence: 99%

Analysing the substrate multispecificity of a proton-coupled oligopeptide transporter using a dipeptide library

et al. 2013

Self Cite

Peptide uptake systems that involve members of the proton-coupled oligopeptide transporter (POT) family are conserved across all organisms. POT proteins have characteristic substrate multispecificity, with which one transporter can recognize as many as 8,400 types of di/tripeptides and certain peptide-like drugs. Here we characterize the substrate multispecificity of Ptr2p, a major peptide transporter of Saccharomyces cerevisiae, using a dipeptide library. The affinities (Ki) of di/tripeptides toward Ptr2p show a wide distribution range from 48 mM to 0.020 mM. This substrate multispecificity indicates that POT family members have an important role in the preferential uptake of vital amino acids. In addition, we successfully establish high performance ligand affinity prediction models (97% accuracy) using our comprehensive dipeptide screening data in conjunction with simple property indices for describing ligand molecules. Our results provide an important clue to the development of highly absorbable peptides and their derivatives including peptide-like drugs.

“…For example, soy peptides, the proteolytic products of soy proteins, can reduce serum lipid levels, scavenge free radicals, and reduce oxidative stress in mammalian cells (6)(7)(8). In yeast, soy peptides improve tolerance to freeze-thaw stress, repress the formation of lipid bodies (9), and accelerate ethanol fermentation (10,11). hPepT1 and hPepT2 are human peptide transporters expressed in the small intestine and the kidney, respectively (12).…”

mentioning

confidence: 99%

Functional Implications and Ubiquitin-Dependent Degradation of the Peptide Transporter Ptr2 in Saccharomyces cerevisiae

et al. 2014

The peptide transporter Ptr2 plays a central role in di-or tripeptide import in Saccharomyces cerevisiae. Although PTR2 transcription has been extensively analyzed in terms of upregulation by the Ubr1-Cup9 circuit, the structural and functional information for this transporter is limited. Here we identified 14 amino acid residues required for peptide import through Ptr2 based on the crystallographic information of Streptococcus thermophilus peptide transporter PepT st and based on the conservation of primary sequences among the proton-dependent oligopeptide transporters (POTs). Expression of Ptr2 carrying one of the 14 mutations of which the corresponding residues of PepT st are involved in peptide recognition, salt bridge interaction, or peptide translocation failed to enable ptr2⌬trp1 cell growth in alanyl-tryptophan (Ala-Trp) medium. We observed that Ptr2 underwent rapid degradation after cycloheximide treatment (half-life, approximately 1 h), and this degradation depended on Rsp5 ubiquitin ligase. The ubiquitination of Ptr2 most likely occurs at the N-terminal lysines 16, 27, and 34. Simultaneous substitution of arginine for the three lysines fully prevented Ptr2 degradation. Ptr2 mutants of the presumed peptide-binding site (E92Q, R93K, K205R, W362L, and E480D) exhibited severe defects in peptide import and were subjected to Rsp5-dependent degradation when cells were moved to Ala-Trp medium, whereas, similar to what occurs in the wild-type Ptr2, mutant proteins of the intracellular gate were upregulated. These results suggest that Ptr2 undergoes quality control and the defects in peptide binding and the concomitant conformational change render Ptr2 subject to efficient ubiquitination and subsequent degradation.