Two systems for phosphate uptake in Yarrowia lipolytica cells grown at acidic conditions

Inorganic phosphate (fi) is accumulated by Yarrowia lipolytica cells grown at acidic pH conditions by two kinetically discrete H+/P-i- cotransport sys tems with apparent K-m values for P-i of 12-18 mu M and 2-3 mM P-i at pH 5. 5, respectively, One of these is derepressible and operates at low external P-i concentrations; the other is most likely constitutively expressed and comas into play at high P-i concentrations. The derepression of the high-af finity P-i transport system is under the control of available extracellular P-i as well as the amount of intracellular polyphosphates stores, Characte ristics of the P-i transport behavior in Yarrowia lipolytica are discussed.