Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fluxes were investigated in growing tubers from wild-type potato (Solanum tuberosum L. cv.Desiree) and from transformants expressing a yeast invertase in the cytosol under the control of the tuber-specific patatin promoter either alone (EC 3.2.1.26;U-IN2-30) or in combination with a Zymomonas mobilis glucokinase (EC 2.7.1.2; GK3-38) by supplying radiolabelled [14C]sucrose, [14C]glucose or [14C]fructose to tuber discs for a 90-min pulse and subsequent chase incubations of 4 and 12 h, and by supplying [14C]fructose for 2 h and 4 h to intact tubers attached to the mother plant. Contrary to the expectation that this novel route for sucrose degradation would promote starch synthesis,the starch content decreased in the transgenic lines.Labelling kinetics did not reveal whether this was due to changes in the fluxes into or out of starch. However,they demonstrated that glycolysis is enhanced in the transgenic lines in comparison to the wild type. There was also a significant stimulation of sucrose synthesis,leading to a rapid cycle of sucrose degradation and resynthesis. The labelling pattern indicated that sucrose phosphate synthase (SPS; EC 2.4.1.14) was responsible for the enhanced recycling of label into sucrose. In agreement, there was a 4-fold and 6-fold increase in the activation status of SPS in U-IN2-30 and GK3-38,respectively, and experiments with protein phosphatase inhibitors indicated that this activation involves enhanced dephosphorylation of SPS. It is proposed that this activation of SPS is promoted by the elevated glucose 6-phosphate levels in the transgenic tubers.These results indicate the pitfalls of metabolic engineering without a full appreciation of the metabolic system and regulatory circuits present in the tissue under investigation.
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PMID:Tuber-specific expression of a yeast invertase and a bacterial glucokinase in potato leads to an activation of sucrose phosphate synthase and the creation of a sucrose futile cycle. 1940 52

In this work, we analyze protein phosphatase (PP) involvement in the sucrose-mediated induction of fructan metabolism in wheat (Triticum aestivum). The addition of okadaic acid (OA), a PP-inhibitor, to sucrose-fed leaves reduced fructosylsucrose-synthesizing activity (FSS) induction in a dose-dependent manner. The expression of the two enzymes that contribute to FSS activity, 1-SST (1-sucrose:sucrose fructosyltransferase, E.C. 2.4.1.99) and 6-SFT (6-sucrose:fructan fructosyltransferase, E.C. 2.4.1.10), was blocked by 1 microM OA. These results suggest the involvement of a PP type 2A in sucrose signaling leading to fructan synthesis. OA addition to the feeding medium impaired both sucrose accumulation in leaves and the expression of sucrose-H+ symporter (SUT1). It is known that sucrose concentration must exceed a threshold for the induction of fructan metabolism; hence PP2A inhibition may result in lower sucrose levels than required for this induction. OA also induced the vacuolar acid invertase (acid INV) transcript levels suggesting that PP activity might play a role in carbon partitioning. Total extractable PP2A activity decreased during 24 h of treatment with sucrose, in parallel with declining sugar uptake into leaf tissues. In conclusion, our results suggest that PP2A is involved in sucrose-induction of fructan metabolism and may play a role in regulating sucrose uptake, but do not rule out that further steps in sucrose signaling pathway may be affected.
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PMID:Protein phosphatase activity and sucrose-mediated induction of fructan synthesis in wheat. 2022 Mar 11