Fatty acid uptake in Candida tropicalis: induction of a saturable process

Abstract

The rates of oleate uptake by Candida tropicalis cells grown on a high oleate concentration (3.5 mM oleate in the presence of 0.50% Brij 58) were higher than those observed in cells grown on glucose; however, oleate uptake was not saturable with substrate concentration. Cells grown at a low oleate concentration (1.0 mM oleate and 2.5% Brij 58) grew to a lower density and at a slightly slower rate; these cells were found to take up oleate at a rate 43-fold higher than cells grown on high oleate concentration. Furthermore, oleate uptake by the cells grown in low oleate medium was a saturable process with Kt and Vmax values of 56 microM and 15 nmol/(min.mg cell protein), respectively. The growth of C. tropicalis under low fatty acid concentration thus clearly results in the induction of a saturable process for its uptake. The total level of acyl-CoA synthetase activity in cells grown on the low oleate concentrations was only twofold higher than in high oleate or glucose grown cells; the level of this enzyme thus does not account for the saturable process and suggests that either the enzyme is regulated in vivo or else a hitherto unidentified enzyme is induced by growth in low concentrations of oleate.

Disruption of the Saccharomyces cerevisiae Homologue to the Murine Fatty Acid Transport Protein Impairs Uptake and Growth on Long-chain Fatty Acids

“…Likewise at 30°C, both strains had comparable apparent K t values (63.5 M for fat1⌬ and 61.5 M for FAT1). These calculated K t values at 30°C are similar to those previously defined in S. cerevisiae and C. tropicalis (17,19). These data are consistent with the notion that Fat1p functions to maximize oleate uptake.…”

“…Kohlwein and Paltauf (16) demonstrated that fatty acid uptake in Saccharomyces uvarum and Saccharomycopsis lipolytica occurs via a saturable process. The same observations were made in Candida tropicalis supporting the hypothesis that fatty acid transport is a facilitated process (17). Knoll et al (19) have shown the uptake of exogenous long-chain fatty acids in S. cerevisiae is saturable and that uptake and activation to CoA thioesters are separable.…”

Ypk1, the yeast orthologue of the human serum- and glucocorticoid-induced kinase, is required for efficient uptake of fatty acids

“…In view of the different growth conditions employed, these kinetic values for wild-type cells are comparable to those previously reported for S. cerevisiae wild-type cells, i.e. 6.54 nmol/minute/10 8 cells (Faergeman et al, 1997;Knoll et al, 1995;Trigatti et al, 1992).…”

“…This assay thus recapitulates key properties of fatty-acid uptake by fungal cells, which have been reported before (Faergeman et al, 1997;Knoll et al, 1995;Kohlwein and Paltauf, 1984;Trigatti et al, 1992).…”

Linoleic Acid Transport by Human Placental Syncytiotrophoblast Membranes

“…These results in combination with our results could explain, in part, the small linoleic acid transfer found in basal plasma membrane, in vitro. In other tissues and whole cells, a saturable transport system recognizes fatty acids with high affinity, and with a K , value in the range 4.5 -16 pM in cultured cardiac cells [27], K, values ranging from 0.3-0.5 pM in adipocytes [37, 381 and a K, value of 56 pM in Candida tropicalis [34]. In these systems, the V, , , values varied from 2.4 pmol .…”