The glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenase and hexokinase interact with cell cycle proteins in maize.

Cyclin/cyclin-dependent kinase (CDK) heterodimers have multiple phosphorylation targets and may alter the activity of these targets. Proteins from different metabolic processes are among the phosphorylation targets, that is, enzymes of central carbon metabolism. This work explores the interaction of Cyc/CDK complex members with the glycolytic enzymes hexokinase 7 (HXK7) and glyceraldehyde-3-phosphate dehydrogenase (GAP). Both enzymes interacted steadily with CycD2;2, CycB2;1 and CDKA;1 but not with CDKB1;1. However, Cyc/CDKB1;1 complexes phosphorylated both enzymes, decreasing their activities. Treatment with a CDK-specific inhibitor (RO-3306) or with lambda phosphatase after kinase assay restored total HXK7 activity, but not GAP activity. In enzymatic assays, increasing concentrations of CDKB1;1, but not of CycD2;2, CycB2;1 or CycD2;2/CDKB1;1 complex, decreased GAP activity. Cell cycle regulators may modulate carbon channeling in glycolysis by two different mechanisms: Cyc/CDK-mediated phosphorylation of targets (e.g., HXK7; canonical mechanism) or by direct and transient interaction of the metabolic enzyme (e.g., GAP) with CDKB1;1 without a Cyc partner (alternative mechanism).

Tetracycline and its quantum dots for recognition of Al3+ and application in milk developing cells bio-imaging.

We developed a technique that detects Al3+ in milk/bio-samples, and reversibly applied to recognize tetracycline (TC) in milk, enhancing the fluorescence intensity without interference from other cations (Cd2+, Ni2+, Co2+, Sr2+, Mg2+, Fe3+, K+, Sm3+, Ag+, Na+, Ba2+, Cr3+, Zn2+ and Mn2+); the limit of detection (LOD) is found to be 0.00022 mM with r2 = 0.9439. The detection of Al3+ is tested in milk as well as in living cells (Saccharomyces cerevisiae and Debaryomyces spp.) by TC or by its quantum dots. This is consistent with the molecular orbital, revealing that the lowering of the energy of HOMO (Highly Occupied Molecular Orbital) discourages the electron transfer from HOMO of fluorophore to HOMO of excited states of Al-complex that increases the fluorescent intensity. Interestingly, carbon dots (CDs) generated from TC also recognize Al3+ as its LOD is as low as to 0.00050 mM with r2 of 0.9404.