Isolation and Characterization of a Gene Specific to Lager Brewing Yeast That Encodes a Branched-Chain Amino Acid Permease

Open Access
Publisher Website
Google Scholar
Abstract
We found two types of branched-chain amino acid permease gene ( BAP2 ) in the lager brewing yeast Saccharomyces pastorianus BH-225 and cloned one type of BAP2 gene (Lg- BAP2 ), which is identical to that of Saccharomyces bayanus (by- BAP2 -1). The other BAP2 gene of the lager brewing yeast (cer- BAP2 ) is very similar to the Saccharomyces cerevisiae BAP2 gene. This result substantiates the notion that lager brewing yeast is a hybrid of S. cerevisiae and S. bayanus . The amino acid sequence homology between S. cerevisiae Bap2p and Lg-Bap2p was 88%. The transcription of Lg- BAP2 was not induced by the addition of leucine to the growth medium, while that of cer- BAP2 was induced. The transcription of Lg- BAP2 was repressed by the presence of ethanol and weak organic acid, while that of cer- BAP2 was not affected by these compounds. Furthermore, Northern analysis during beer fermentation revealed that the transcription of Lg- BAP2 was repressed at the beginning of the fermentation, while cer- BAP2 was highly expressed throughout the fermentation. These results suggest that the transcription of Lg- BAP2 is regulated differently from that of cer- BAP2 in lager brewing yeasts.