Novel transporters from Kluyveromyces marxianus and Pichia guilliermondii expressed in Saccharomyces cerevisiae enable growth on l‐arabinose and d‐xylose

Genes encoding l ‐arabinose transporters in Kluyveromyces marxianus and Pichia guilliermondii were identified by functional complementation of Saccharomyces cerevisiae whose growth on l ‐arabinose was dependent on a functioning l ‐arabinose transporter, or by screening a differential display library, respectively. These transporters also transport d ‐xylose and were designated KmAXT1 (arabinose–xylose transporter) and PgAXT1, respectively. Transport assays using l ‐arabinose showed that KmAxt1p has K_m 263 mm and V_max 57 nm /mg/min, and PgAxt1p has K_m 0.13 mm and V_max 18 nm /mg/min. Glucose, galactose and xylose significantly inhibit l ‐arabinose transport by both transporters. Transport assays using d ‐xylose showed that KmAxt1p has K_m 27 mm and V_max 3.8 nm /mg/min, and PgAxt1p has K_m 65 mm and V_max 8.7 nm /mg/min. Neither transporter is capable of recovering growth on glucose or galactose in a S. cerevisiae strain deleted for hexose and galactose transporters. Transport kinetics of S. cerevisiae Gal2p showed K_m 371 mm and V_max 341 nm /mg/min for l ‐arabinose, and K_m 25 mm and V_max 76 nm /mg/min for galactose. Due to the ability of Gal2p and these two newly characterized transporters to transport both l ‐arabinose and d ‐xylose, one scenario for the complete usage of biomass‐derived pentose sugars would require only the low‐affinity, high‐throughput transporter Gal2p and one additional high‐affinity general pentose transporter, rather than dedicated d ‐xylose or l ‐arabinose transporters. Additionally, alignment of these transporters with other characterized pentose transporters provides potential targets for substrate recognition engineering. Accession Nos: KmAXT1: GZ791039; PgAXT1: GZ791040 Copyright © 2015 John Wiley & Sons, Ltd.