Cacao

Figure 1 (a) does indicate that BAP2 is involved in high affinity transport when ammonium is present in the medium compared to low affinity transport. This was shown by a mutation in BAP2 causing severely reduced transport in a low concentration of phenylalanine and less reduced transport in a high concentration of phenylalanine. However, this does not indicates that BAP2 is the major high affinity phenylalanine permease; it depends on the conditions. GAP1 is the general major high affinity permease but it is inactivated by the presence of ammonium. When ammonium is not present in the medium, the transport of phenylalanine in the BAP2 mutant remains only slightly reduced. Thus BAP2 is the major high affinity transporter when GAP1 is inactivated.

When double mutants are made, (Figure 1 (c) and (d)) the uptake of GAP1/BAP2 is not near as reduced as the GAP1/AGP1 mutant in both phenylalanine concentrations. This indicates that AGP1 is the primary transporter when GAP1 is disrupted. The inactivation and disruption of GAP1 are not equivalent and cause different results.