Modulation of auxin formation by the cytosolic phenylalanine biosynthetic pathway.

In plants, phenylalanine biosynthesis occurs via two compartmentally separated pathways. Overexpression of petunia chorismate mutase 2 (PhCM2), which catalyzes the committed step of the cytosolic pathway, increased flux in cytosolic phenylalanine biosynthesis, but paradoxically decreased the overall levels of phenylalanine and phenylalanine-derived volatiles. Concomitantly, the levels of auxins, including indole-3-acetic acid and its precursor indole-3-pyruvic acid, were elevated. Biochemical and genetic analyses revealed the existence of metabolic crosstalk between the cytosolic phenylalanine biosynthesis and tryptophan-dependent auxin biosynthesis mediated by an aminotransferase that uses a cytosolic phenylalanine biosynthetic pathway intermediate, phenylpyruvate, as an amino acceptor for auxin formation.

Phospho Tensin Homolog in Human and Lipid Peroxides in Peripheral Blood Mononuclear Cells Following Exposure to Flavonoids.

Objectives: Studies have shown that human and peripheral blood mononuclear cells (PBMCs) are mostly used for research purposes to study several biochemical endpoints. The effects of the flavonoids, genistein, kaempferol, and quercetin on phospho tensin homolog (PTEN) levels in cancer cells (i.e., breast [BT549], lung [A549]), human embryonic kidney cells (HEK293), and the levels of lipid peroxides (LP) in PBMCs were respectively investigated.Materials and methods: Cancer, kidney, and PBMCs from several donors were each exposed to each of the flavonoids at concentrations of 0, 5, 10, 15, 20, and 25 µM. Our hypotheses were that exposure of cancer and kidney cells to genistein, kaempferol, and quercetin can increase PTEN and decrease lipid peroxides in PBMCs levels respectively to better cope with oxidative stress.Results: The results indicate that the flavonoids increased total PTEN levels in a dose-dependent manner. The effect of quercetin was more pronounced followed by genistein and kaempferol. Furthermore, decreases in lipid peroxides were observed in the PBMCs for the flavonoid-treated samples compared to those exposed to flavonoids and with oxidative stress as described by Fenton's chemistry. Levels of LP in quercetin-treated samples were lower compared to kaempferol and genistein.Conclusions: The findings suggest that the flavonoids play an important role in controlling oxidative stress in several human cells.