| Summary: | We have functionally characterized the four Saccharomyces cerevisiae (Sc) Jen1 homologues of Debaryomyces hansenii (Dh) by heterologous expression in S. cerevisiae. Debaryomyces hansenii cells display mediated transport for the uptake of lactate, acetate, succinate and malate. DHJEN genes expression was detected by RT-PCR in all carbon sources assayed, namely lactate, succinate, citrate, glycerol and glucose. The heterologous expression in the S. cerevisiae W303-1A jen1 Lambda ady2 Lambda strain demonstrated that the D. hansenii JEN genes encode four carboxylate transporters. DH27 gene encodes an acetate transporter (K-m 0.94 +/- 0.17 mM; V-max 0.43 +/- 0.03 nmol s(-1) mg(-1)), DH17 encodes a malate transporter (K-m 0.27 +/- 0.04 mM; V-max 0.11 +/- 0.01 nmol s(-1) mg(-1)) and both DH18 and DH24 encode succinate transporters with the following kinetic parameters, respectively, K-m 0.31 +/- 0.06 mM; V-max 0.83 +/- 0.04 nmol s(-1) mg(-1)and K-m 0.16 +/- 0.02 mM; V-max 0.19 +/- 0.02 nmol s(-1) mg(-1). Surprisingly, no lactate transporter was found, although D. hansenii presents a mediated transport for this acid. This work advanced the current knowledge on yeast carboxylate transporters by characterizing four new plasma membrane transporters in D. hansenii.
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