## 3 Results and Discussion
### Amino Acid Transport  
Amino acids are involved in numerous metabolic pathways. _S. cerevisiae_ can synthesize them _de novo_; they are also actively imported from the extracellular environment. This is less expensive in terms of energy; the estimated cost of _de novo_ amino acid synthesis under aerobic conditions is between 9.5 ATP for glutamate and 75.5 ATP for tryptophan [19]. Yeast export of amino acids enables them to respond to different environments and take advantage of available resources. The amino acids present in the vacuole are histidine, lysine, and arginine, constituting 80 to 90%, while a similar fraction of glutamate and aspartate is present in the cytosol [20; 21; 22]. _S. cerevisiae_ incorporates amino acids from the medium, making use of proteins known as amino acids permeases by a simport mechanism [23]. The multiplicity and diversity of transporters allows yeast to accumulate amino acids for biosynthesis and catabolism under multiple conditions and in a wide range of external concentrations [24]. Of the total transporters identified in _S. cerevisiae_ (41 transporters) [19], 6 transporters (Avt\(\mathcal{V}\)p, Bap2p, Lst4p, Put4p, Uga4p, Ydl119 cp) in MF and 1 (Npr2p) in EF have been obtained in the P29 strain. While in the G1 strain, 5 (Alp1p, Avt4p, Btn2p, Gnp1p, Ssy1p) in MF and 0 in EF have been reported. In view of these results, it would not be expected to find a great difference between the two strains. However, the transporters identified in both types of yeast were different, although all transport the full range of amino acids from the cell exterior to the interior and from the cell interior to the vacuole or mitochondria. Of the transporters identified in the P29 strain, Avt\(\mathcal{V}\)p was the one with the highest protein content (0.028 mol%). Data are shown in Table 2. Yeast Avt\(\mathcal{V}\) proteins can be subdivided into four main groups, defined as Avt1p, Avt2p, Avt3p/4p, and Avt5p/6p/7p [25]. Avt1p intervenes in the active absorption of amino acids in the vacuole, while Avt3p, Avt4p, and Avt6p are involved in the active exit of amino acids from the vacuole into the \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{**Middle of the Second Fermentation, MF**} \\ \cline{2-5}  & \multicolumn{1}{c}{**P29 Strain**} & \multicolumn{2}{c}{**G1 Strain**} \\ \hline
**Biological Process** & **Specific Proteins** & **Specific/Total Proteins** & **Specific Proteins** & **Specific/Total Proteins** \\ \hline tRNA aminoacid & Aim10p, Cdc0p, Ded81p, & & & \\ for protein translation & Dia4p, Dps1p, Msk1p, Slm5p, & & & \\ (GO: 0006418) & Ths1p, Wns1p & & & \\ \hline Amino acid transport & Avt\(\mathcal{V}\)p, Bap2p, Lst4p, Put4p, & & & \\ (GO: 0006865) & Uga4p, Ydl119 cp & & & \\ \hline  & \multicolumn{4}{c}{**End of the second fermentation, EF**} \\ \cline{2-5}  & \multicolumn{1}{c}{**P29 Strain**} & \multicolumn{2}{c}{**G1 Strain**} \\ \hline
**Biological Process** & **Specific Proteins** & **Specific/Total Proteins** & **Specific Proteins** & **Specific/Total Proteins** \\ \hline  & Ade3p, Adh3p, Arg1p, Arg7p, & & & \\  & Arg8p, Arg8p, Arg8p, Arg82p, Arolp1p, & & & \\  & Aro2p, Arso3p, Asn1p, Asn2p, & & & \\  & Ben1p, Carlp, Carl2p, Cys3p, & & & \\  & Cys4p, Dtd1p, Gdh1p, Gln1p, & & & \\  & Gus1p, Hsi4p, Hom6p, Hpq3p, & & 43/56 & Met13p, Met8p, Sno3p, & 9/22 \\  & Idh1p, Il9 cp, Kgd2p, Leutp, & & & Sn21p, Ybr145 wp \\  & Lpt4p, Lys12p, Lys20p, Mcm1p, & & & \\  & Met17p, Mis1p, Mmf1p, Pro2p, & & & \\  & Sam2p, Ser1p, Ser3p, Sfa1p, & & & \\  & Shm2p, Uga1p, Yhr208 wp & & & \\ \hline tRNA aminoacid & & & & \\ for protein translation & Arclp, Grs1p, Gus1p, Ismlp, & & & \\ (GO: 0006418) & Msk1p, Ses1p, Vas1p & & & \\ \hline Amino acid transport & & & & \\ (GO: 0006865) & Npr2p & 1/1 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._cytosol. Avt7p is located in the vacuolar membrane of _S. cerevisiae_ and participates in the vacuolar absorption of glutamine and proline and in the formation of spores in _S.