The competing solute analyses show that acetate- and MCA-grown cells have similar inhibition pattern for acetate uptake. This suggested that the acetate-transport system was likely to be induced by MCA. The relatively selleck inhibitor lower acetate-uptake rate for MCA-grown cells suggested that MCA was a weaker inducer. This is consistent with the observation

that acetate and propionate were the best inducers for acetate uptake. The competing solute analyses for MCA-grown cells show that the cells have different inhibition patterns for acetate- and MCA- uptake. The check details failure of MCA to inhibit the uptake of acetate suggested that the acetate-transport system was expressed and not involved in MCA transport. This is in agreement with the result that acetate-grown cells failed to transport MCA. The ability for acetate to inhibit the MCA-uptake activity of MCA-grown cells concluded that the MCA-uptake activity is

different from the acetate-uptake system. The effect of pH on the uptakes of acetate of acetate- and MCA-grown cells further demonstrates the presence of two systems. The uptake rates of acetate-grown cells decrease linearly with an increase in pH. This shows that proton plays an essential role in the acetate-uptake system. In this condition no MCA-uptake system was produced. When the cells were grown on MCA the rates of acetate uptake on different pH deviate from selleck that of acetate-grown cells. The competing solute analysis demonstrated a similar pattern of inhibition on acetate uptake for acetate- and MCA-grown cells while the rate was much lower for the latter. It is most likely that the expression

of the acetate-uptake system was lower in MCA-grown cells. In this case, the major transport system was that for MCA and which can also transport acetate. Since both acetate- and MCA- transport systems are proton dependent, the pH dependency of acetate uptake of MCA-grown cells was thus exhibiting a pattern different from that of acetate-grown cells and was displaying a hybrid pattern between acetate uptake of acetate-grown very cells and MCA uptake of MCA-grown cells. Future experiments that assay the pH dependency of acetate uptake of MCA-grown Ins-4p-p2 double mutant could clarify the situation. However, the expressions of other transporters may be affected by the disruptions of deh4p and dehp2 [15] and could complicate the outcome. Moreover, when the gene responsible for the acetate-uptake system has been identified, it is necessary to measure its expression levels in medium containing acetate, MCA and other substrates in order to characterize the system fully. The most distinct difference between the two transport systems is their substrate specificity. The failure of ethanol to inhibit acetate transport suggested that the carboxyl group is likely to be an important element. The lack of inhibition by formate implied that the presence of a second carbon is also essential.