Characterization ofl-leucine transport in the opportunistic yeastsMalassezia furfur andMalassezia pachydermatis

The lipophilic yeastsMalassezia furfur andM. pachydermatis show an initial rapid uptake ofl-leucine followed by slower steady-state rates. At least two independent transport systems forl-leucine were present in both species. The high-affinity system forM. furfur had a K_T of 0.047 µM with a J_max of 222 fM/min/10⁶ cells (65 pM/min/mg dry weight), whereas forM. pachydermatis the K_T was 0.067 µM with a J_max of 709 fM/min/10⁶ cells (89 pM/min/dry weight). The low-affinity system forM. furfur had a K_T of 646 µM with a J_max of 1.62 pM/min/10⁶ cells (0.5 nM/min/mg dry weight) and that ofM. pachydermatis had a K_T of 3.3 µM with a J_max of 9.97 pM/min/10⁶ cells (1.3 nM/min/mg dry weight). Both transport systems were energy-dependent. Cells incubated with Tween 80 showedl-leucine uptake via both transport systems. Cells incubated with a combination of glucose (1%) and Tween 80 (0.01%) showed decreased transport rates for the high-affinity system for both species as compared with cells incubated only with glucose. The low-affinity transport system of both species in the presence of glucose plus Tween 80 showed an initial rapid uptake followed by greater efflux than influx ofl-leucine.l-Leucine demonstrated binding to Tween 80, but the major effect of Tween 80 on membrane transport inMalassezia appears to be on the efflux of transported molecules.