Comparative proteomes of Corynebacterium glutamicum grown on aromatic compounds revealed novel proteins involved in aromatic degradation and a clear link between aromatic catabolism and gluconeogenesis via fructose-1,6-bisphosphatase

The current study examined the aromatic degradation and central metabolism in Corynebacterium glutamicum by proteomic and molecular methods. Comparative analysis of proteomes from cells grown on gentisate and on glucose revealed that 30% of the proteins of which their abundance changed were involved in aromatic degradation and central carbon metabolism. Similar results were obtained from cells grown on benzoate, 4-cresol, phenol, and resorcinol. Results from these experiments revealed that (i) enzymes involved in degradation of benzoate, 4-cresol, gentisate, phenol, and resorcinol were specifically synthesized and (ii) that the abundance of enzymes involved in central carbon metabolism of glycolysis/gluconeogenesis, pentose phosphate pathway, and TCA cycles were significantly changed on various aromatic compounds. Significantly, three novel proteins, NCgl0524, NCgl0525, and NCgl0527, were identified on 4-cresol. The genes encoding NCgl0525 and NCgl0527 were confirmed to be necessary for assimilation of 4-cresol with C. glutamicum. The abundance of fructose-1,6-bisphosphatase (Fbp) was universally increased on all the tested aromatic compounds. This Fbp gene was disrupted and the mutant WT(Deltafbp) lost the ability to grow on aromatic compounds. Genetic complementation by the Fbp gene restored this ability. We concluded that gluconeogenesis is a necessary process for C. glutamicum growing on various aromatic compounds.     

Proteomic analysis of soybean nodule cytosol

An isolation procedure for soybean (Glycine max L. cv Williams 82) nodule cytosol proteins was developed which greatly improved protein resolution by two-dimensional polyacrylamide gel electrophoresis. The most abundant proteins were selected and analyzed by mass spectrometry. The identified proteins were categorized by function (% of total proteins analyzed): carbon metabolism (28%), nitrogen metabolism (12%), reactive oxygen metabolism (12%) and vesicular trafficking (11%). The first three categories were expected based on the known physiological functions of the symbiotic nitrogen fixation process. The number of proteins involved in vesicular trafficking suggests a very active exchange of macromolecules and membrane components. Among the 69 identified proteins were the enzymes of the three carbon portion of glycolysis, which were further characterized to support their roles in the sucrose synthase pathway to provide malate for the bacteroids. Proteomic analysis provides a functional tool by which to understand and further investigate nodule function.     

Pharmacologic intervention targeting glycolytic‐related pathways protects against retinal injury due to ischemia and reperfusion

Retinal ischemia contributes to multiple ocular diseases while aminoguanidine (AMG) treatment significantly inhibits the neuronal and vascular degeneration due to acute retinal ischemia and reperfusion (I/R) injury. In the present study, 2‐D DIGE was applied to profile global protein expression changes due to retinal I/R injury, and the protection effects mediated by AMG. Retinal ischemia was induced by elevated intraocular pressure to 80–90 mmHg for 2 h, and reperfusion was established afterward. Retinal tissues were collected 2 days after I/R injury. After 2‐D DIGE analysis, a total of 96 proteins were identified. Among them, 28 proteins were identified within gel spots whose intensities were normalized by AMG pretreatment, pathway analysis indicated that most were involved in glycolysis and carbohydrate metabolism. Selected enzymes identified by MS/MS within these pathways, including transketolase, triosephosphate isomerase 1, aldolase C, total enolase, and pyruvate kinase were validated by quantitative Western blots. Glycolytic enzymes and other differentially regulated proteins likely play previously unrecognized roles in retinal degeneration after I/R injury, and inhibition of the resulting metabolic changes, using pharmacologically agents such as AMG, serve to inhibit the changes in metabolism and mitigate retinal degeneration. Select glycolytic enzymes may provide novel therapeutic targets for inhibiting the neuronal and vascular degeneration after retinal I/R injury.     

Dysregulation of glucose transport, glycolysis, TCA cycle and glutaminolysis by oncogenes and tumor suppressors in cancer cells

A common set of functional characteristics of cancer cells is that cancer cells consume a large amount of glucose, maintain high rate of glycolysis and convert a majority of glucose into lactic acid even in the presence of oxygen compared to that of normal cells (Warburg's Effects). In addition, cancer cells exhibit substantial alterations in several energy metabolism pathways including glucose transport, tricarboxylic acid (TCA) cycle, glutaminolysis, mitochondrial respiratory chain oxidative phosphorylation and pentose phosphate pathway (PPP). In the present work, we focused on reviewing the current knowledge about the dysregulation of the proteins/enzymes involved in the key regulatory steps of glucose transport, glycolysis, TCA cycle and glutaminolysis by several oncogenes including c-Myc and hypoxia inducible factor-1 (HIF-1) and tumor suppressor, p53, in cancer cells. The dysregulation of glucose transport and energy metabolism pathways by oncogenes and lost functions of the tumor suppressors have been implicated as important biomarkers for cancer detection and as valuable targets for the development of new anticancer therapies.