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Mapping Post-Translational Modifications of de Novo Purine Biosynthetic Enzymes: Implications for Pathway Regulation
journal contribution
posted on 2019-04-09, 00:00 authored by Chunliang Liu, Giselle M. Knudsen, Anthony M. Pedley, Jingxuan He, Jared L. Johnson, Tomer M. Yaron, Lewis C. Cantley, Stephen J. BenkovicPurines
represent a class of essential metabolites produced by
the cell to maintain cellular homeostasis and facilitate cell proliferation.
In times of high purine demand, the de novo purine biosynthetic pathway
is activated; however, the mechanisms that facilitate this process
are largely unknown. One plausible mechanism is through intracellular
signaling, which results in enzymes within the pathway becoming post-translationally
modified to enhance their individual enzyme activities and the overall
pathway metabolic flux. Here, we employ a proteomic strategy to investigate
the extent to which de novo purine biosynthetic pathway enzymes are
post-translationally modified in 293T cells. We identified 7 post-translational
modifications on 135 residues across the 6 human pathway enzymes.
We further asked whether there were differences in the post-translational
modification state of each pathway enzyme isolated from cells cultured
in the presence or absence of purines. Of the 174 assigned modifications,
67% of them were only detected in one experimental growth condition
in which a significant number of serine and threonine phosphorylations
were noted. A survey of the most-probable kinases responsible for
these phosphorylation events uncovered a likely AKT phosphorylation
site at residue Thr397 of PPAT, which was only detected in cells under
purine-supplemented growth conditions. These data suggest that this
modification might alter enzyme activity or modulate its interaction(s)
with downstream pathway enzymes. Together, these findings propose
a role for post-translational modifications in pathway regulation
and activation to meet intracellular purine demand.
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293 T cellspurine-supplemented growth conditionsAKT phosphorylation site7 post-translational modificationspost-translational modification stateNovo Purine Biosynthetic Enzymespurine biosynthetic pathway enzymesPathway Regulation Purinesintracellular purine demandresidue Thr 397pathway enzymesPPATpurine biosynthetic pathwayMapping Post-Translational Modifications
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