Possible Interaction: Vitamin B 6 and Alpha-Ketoglutarate

“NMR spectral features of selected metabolites indicated that vitamin B-6 restriction significantly increased the ratios of glutamine/glutamate and 2-oxoglutarate/glutamate (P<0.001) and tended to increase concentrations of acetate, pyruvate, and trimethylamine-N-oxide (adjusted P<0.05).”

“Preincubation of nervous tissue with pyridoxal-5'-phosphate (40 microM) results in significant acceleration of catabolism of [1-14C] alpha-ketoglutarate , [5-14C] alpha-ketoglutarate and [4-14C] aspartate with an inconsiderable increase of catabolism of the rest of labelled substrates.”

“… pyridoxal-5-phosphate … alpha-ketoglutarate blocked the NADH-induced GTP binding site and the disappearance of positive kinetic cooperativity induced by GTP was observed; to achieve the … by GTP depends probable on the cooperative character of interaction between the two molecules of GTP to each protomer of the enzyme.”

“Formation of a nonproductive adsorption complex of the pyridoxal enzyme with 2-oxoglutarate or of the pyridoxamine enzyme with glutamate alters the exchange characteristics only slightly.”

“In initial-rate experiments, pyridoxal 5'-phosphate , used as an instantaneous inhibitor rather than a long-term inactivator, displayed non-competitive inhibition with respect to both 2-oxoglutarate and NADH.”

“These results clearly indicate that, although there is mutual hindrance between the binding to the enzyme of pyridoxal 5'-phosphate , on the one hand, and 2-oxoglutarate or NADH on the other, binding is not mutually exclusive.”

“4–6 h after a compound was administered, δ-aminolevulinate synthesis in liver mitochondria was increased eight-fold; the synthesis required addition of greater amounts of pyridoxal phosphate , magnesium, and phosphate to the medium, but 2-ketoglutarate was inhibitory.”

“The mitochondria readily oxidized aspartate (Asp) or alpha-KG individually with low rates, while they oxidized Asp and alpha-KG simultaneously with high rates, and this simultaneous oxidation was also inhibited by PLP.”