Abstract
The biological and chemical basis of vanadium action in fungi is relatively poorly understood. In the present study, we investigate the influence of vanadate (V5+) on phosphate metabolism of Phycomyces blakesleeanus. Addition of V5+ caused increase of sugar phosphates signal intensities in 31P NMR spectra in vivo. HPLC analysis of mycelial phosphate extracts demonstrated increased concentrations of glucose 6 phosphate, fructose 6 phosphate, fructose 1, 6 phosphate and glucose 1 phosphate after V5+ treatment. Influence of V5+ on the levels of fructose 2, 6 phosphate, glucosamine 6 phosphate and glucose 1, 6 phosphate (HPLC), and polyphosphates, UDPG and ATP (31P NMR) was also established. Increase of sugar phosphates content was not observed after addition of vanadyl (V4+), indicating that only vanadate influences its metabolism. Obtained results from in vivo experiments indicate catalytic/inhibitory vanadate action on enzymes involved in reactions of glycolysis and glycogenesis i.e., phosphoglucomutase, phosphofructokinase and glycogen phosphorylase in filamentous fungi.
Highlights
Vanadium is widely spread, naturally occurring, multivalent transition metal, existing in nature mostly in 5+ and 4+ oxidation states
The 31P NMR spectroscopy was used to monitor the action of vanadium on the level of phosphate compounds in fungus P. blakesleeanus
The intensity of signal assigned to the core polyphosphate residues (PPc) increased by 40%, while the intensity of Pi signal decreased by 21.5%, i.e., V5+ caused a decrease of PPc/Pi signal intensity ratio by 67.8%
Summary
Naturally occurring, multivalent transition metal, existing in nature mostly in 5+ and 4+ oxidation states It is essential in micromolar concentrations for many eukaryotic organisms, but at higher concentrations it is toxic and can represent an environmental threat [1]. Even though both oxidation states of vanadium can alter enzyme activities, those involved in splitting a phosphate ester linkage [2], such effect is attributed mainly to vanadate (V5+) and arises from its structural and electronic similarity to phosphate [3], [4]. It has stimulatory effect on glucose 6 phosphate dehydrogenase, ribulose 5 phosphate epimerase, phosphoglucose isomerase and adenylyl cyclase [10]
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