Effect of amino acids on peptide transport in sake yeast

The PTR2 gene of Saccharomyces cerevisiae encodes a major peptide permease responsible for the uptake of low-molecular-weight peptides consisting of two or three amino acids. We show that the PTR2 gene of sake yeast encodes a major peptide permease in the main mash of sake brewing. The peptide uptake activity in sake yeast is decreased by the addition of certain types of amino acids, particularly asparagine, serine and lysine. Northern blot analysis suggested that asparagine and serine repress the expression of the PTR2 gene, but lysine decreases the peptide transport activity without repressing PTR2 gene transcription. The deletion analysis of the PTR2 promoter region confirmed these suggestions and revealed that the cis-element involved in the regulation of the PTR2 gene by amino acids is located in the region from residue −400 to the start codon.