The lipophilic yeasts Malassezia furfur and M. pachydermatis show an initial rapid uptake of L-leucine followed by slower steady-state rates. At least two independent transport systems for L-leucine were present in both species. The high-affinity system for M. furfur had a K(T) of 0.047-mu-M with a J(max) of 222 fM/min/10(6) cells (65 pM/min/mg dry weight), whereas for M. pachydermatis the K(T) was 0.067-mu-M with a J(max) of 709 fM/min/10(6) cells (89 pM/min/dry weight). The low-affinity system for M. furfur had a K(T) of 046-mu-M with a J(max) of 1.62 pM/min/10(6) cells (0.5 nM/min/mg dry weight) and that of M. pachydermatis had a K(T) of 3.3-mu-M with a J(max) of 9.97 pM/min/10(6) Cells (1.3 nM/min/mg dry weight). Both transport systems were energy-dependent. Cells incubated with Tween 80 showed L-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 of L-leucine. L-Leucine demonstrated binding to Tween 80, but the major effect of Tween 80 on membrane transport in Malassezia appears to be on the efflux of transported molecules.