## 4 Discussion
Differences in NCR-sensitive genes (e.g., ILV5 and LYS9) and TCA cycle proteins (KGD1 and ACO2) suggest the strain-specific modulation of the TOR and SPS sensing pathways. N62's emphasis on glycolysisand amino acid transporters aligns with the nitrogen-efficient phenotypes suitable for biofuel production, while G1's stress-responsive proteins (EXG1 and ERG8) may enhance robustness in nitrogen-poor environments. Among the nitrogenous compounds studied in this work, only two biogenic amines were detected in the wines produced, namely putrescine and tyramine, the former being more abundant. Biogenic amines are produced via the decarboxylation of the corresponding amino acid precursors via yeast activity during alcoholic fermentation [10]. The precursors of putrescine (aliphatic biogenic amine) are the amino acids ornithine and arginine [30], and the precursor of tyramine (aromatic biogenic amine) is tyrosine [31]. The wines were made under the same conditions, with the same base wine, but with two different strains of _S. cerevisiae_, and the results showed that the wine made with strain N62 produced significantly higher concentrations of the two biogenic amines. Some of the reasons for this may be that this strain consumes L-arginine and has a higher decarboxylation capacity [32]. The tricarboxylic acid (TCA) cycle plays an important role in lipid synthesis, amino acid synthesis, and energy (ATP) production. It enables cell growth and is considered the metabolic backbone of the cell, and the glyoxylate cycle is considered an auxiliary pathway [33]. Several proteins with significant TCA-related differences were identified in strain N62. The proteins HXK1, HXK2, ENO1, and ENO2, which are responsible for the production of pyruvate, have been quantified with significant differences in this strain [34]. In particular, the two enolases form phosphoenolpyruvate, an intermediate in the tyrosine pathway [35], which also shows significant differences in this strain. In contrast, tyrosine can be catalyzed via the Ehrlich pathway to form \(\alpha\)-ketoacids [36], as may occur in strain G1. Another way to synthesize pyruvate is through the conversion of the malate produced in TCA, with the protein responsible being MAE1 [37], which showed significant differences for strain N62. L-leucine is an essential amino acid synthesized from pyruvate. As mentioned above, strain N62 is the yeast that would be producing more pyruvate, so this could explain the concentration of this amino acid found in this wine, as well as the significant differences with respect to the base wine and the wine inoculated with the other strain [38]. According to [PERSON] et al. [27], when there is a high nitrogen content in the base wine, a large percentage of L-leucine can be metabolized by the yeast, as the results have shown (Figure 3c) in strain G1. At the onset of fermentation, it would be incorporated significantly and could be used for protein synthesis [39]. L-alanine can be transformed from pyruvate and ammonia after the decarboxylation of aspartic acid [40]. The high availability of ammonium ion and the consumption of aspartic acid could explain the significantly different synthesis of this amino acid in the N62 strain. Valine is also generated from pyruvate via animation [41]. In strain G1, it was completely consumed for direct incorporation into proteins [42], but in wine inoculated with N62, quantitative differences were obtained with respect to the other strain and the base wine, which could be due to the fact that its biosynthetic pathway is very similar to that of alanine and leucine [41]. In addition, a protein, ILV5, was quantified with significant differences for this strain, which is involved in the L-valine synthesis pathway [43] and VAS1, a specific protein for strain N62 related to this amino acid [44] (Figure 7). The proteins that convert pyruvate to acetyl-CoA also showed significant differences; they are LAT1, LPD1, and PDA1 (see Figure 6b), all of which are positively regulated for the N62 strain.