4.1.2. Carbon source-regulated protein acetylation
Comparative studies with different carbon sources have explored the
effect of protein acetylation during growth under glycolytic and
oxidative conditions. As Wang and collaborators demonstrated, S.
enterica presents changes in cell growth and significant difference in
the percentage of acetylated proteins in response to glucose or citrate.
A total of 15 enzymes were identified with altered acetylation status in
response to a carbon source, and all of them showed higher acetylation
levels in cells grown in glucose (Wang et al., 2010). The main targets
of lysine acetylation were enzymes involved in central metabolism, and a
correlation was observed in the cell growth and the acetylation levels
on these proteins; in a medium containing glucose, cells grow faster,
and an increase in the acetylation of central metabolic enzymes was
observed, but when the acetylation decreases, opposite growth properties
were observed (Wang et al., 2010). In Bacillus subtilis ,
different acetylation levels have also been reported in different carbon
sources. in decreasing order, protein acetylation occurs in a medium
containing only carbon source pyruvate, glucose, glycerol, or citrate.
(Kosono et al., 2015). The main differences in the acyl modification
patterns were observed in glucose and citrate. In fact, it was under
these two conditions that changes in the acetylation sites were
determined. Acetylation was upregulated at 13 sites in the glucose
condition relative to the citrate condition, and as in S.
enterica , acetylation positively modulated the growth of this bacterium
in glucose-medium (Kosono et al., 2015). Western immunoblot analysis
found that glucose and lactate produce global acetylation in E.
coli K-12, which increased after the cells had entered the stationary
phase. Induction of acetylation at this growth point requires continue
exposure to carbon sources, specifically glucose (Schilling et al.,
2015). The results suggest that the protein acetylation may have a
physiological role in mediating adaptation to different carbon sources.
Another factor that could determine the lysine acetylation levels is the
sugar amount. In E. coli, there is no difference in acetylation
patterns during growth in glucose or xylose as the sole carbon source.
However, an increase in the relative abundance of acetylation at high
concentrations of these two carbohydrates has been observed, indicating
that acetylation only sometimes has a regulatory role in obtaining
specific carbon sources
(Schilling et al., 2019). Also,
acetylation increases in parallel with glucose consumption and acetate
excretion (Schilling et al., 2015; Schilling et al., 2019). The results
support the hypothesis that protein acetylation regulates metabolism in
response to energy status, mainly when the carbon flux exceeds the
capacity of the tricarboxylic acid (TCA) cycle, resulting in overflow
metabolism (Schilling et al., 2015; Schilling et al., 2019).