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Characterization of the Saccharomyces bayanus ‐type AGT1 transporter of lager yeast
Author(s) -
Vidgren Virve,
Londesborough John
Publication year - 2012
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/jib.22
Subject(s) - maltotriose , maltose , yeast , saccharomyces cerevisiae , biology , biochemistry , saccharomyces , lactose permease , atp binding cassette transporter , transporter , membrane transport protein , gene , sucrose
Transport of maltose and maltotriose into the yeast cell is thought to be rate‐limiting in the utilization of these sugars. The maltose and maltotriose transporters Malx1, Agt1, Mtt1 and Mphx are present in different combinations in brewer's yeast strains, conferring different maltose and maltotriose transport characteristics on the strains. A new putative maltose/maltotriose transporter ORF was identified during whole genome sequencing of the lager strain WS34/70 (Y. Nakao et al. , DNA Res ., 2009, 16, 115–129). Sequence comparisons suggested that this putative α ‐glucoside transporter might be a Saccharomyces bayanus counterpart of the Agt1 ( Saccharomyces cerevisiae type) transporter. In the present work, the transporter coded by a SbAGT1 gene from a lager strain, A15 (and with the same sequence as the corresponding gene in WS34/70) was characterized. It is shown that this SbAGT1 encodes a functional α ‐glucoside transporter with a wide‐substrate range, including maltose and maltotriose. Trehalose, α ‐methylglucoside and sucrose were inhibitors, suggesting they are also substrates. The SbAgt1 transporter had similar affinities for maltose and maltotriose (17 ± 7 and 22 ± 2 m m , respectively) and a higher V max for maltose than maltotriose (21 ± 7 and 12 ± 2 µmol min −1 g dry yeast −1 , respectively). Copyright © 2012 The Institute of Brewing & Distilling