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.