Glucose consumption, inhibition

The regulation of glycolysis by allosteric activation or inhibition, or the phosphorylation/dephosphorylation of rate-limiting enzymes, is shortterm—that is, they influence glucose consumption over periods of minutes or hours. Superimposed on these moment-to-moment effects are slower, often more profound, hormonal influences on the amount of enzyme protein synthesized. These effects can result in ten-fold to twenty-fold increases in enzyme activity that typically occur over hours... 

The present study investigated the inhibition of Saccharomyces cerevisiae by the liquid hydrolysate and the kinetics of enzymatic hydrolysis of the solid components produced by the pretreatment of aspen wood and corn stover by liquid hot water and hot carbonic acid. Inhibition of yeast was determined by measuring the rate of glucose consumption by yeast growing in hydrolysates produced at various reaction severities. The enzymatic hydrolysis rates of pretreated solids was determined by measuring rates of sugar accumulation of enzyme-digested pretreated solids. 

Figure 1 shows that with aspen wood as the substrate, glucose consumption by yeast was inhibited by the hydrolysate and that the inhibition increased as the severity of the pretreatment increased. However, there was no difference in the amount or rate of glucose consumed between samples that were pretreated with C02 and samples pretreated without CQ2. 

At the lowest tested severity parameter of 180°C for 8 min, there was almost no inhibition when compared to the control that was run at each experiment. However, at the highest tested severity parameter of 220°C for 32 min, there was an almost 50% reduction in the rate of glucose consumption by the yeast. This division of inhibition as it correlates to severity is well defined for both the aspen wood and corn stover samples. However, between the aspen wood and corn stover samples there appeared to be a difference in inhibition rates, as a comparison of Figs. 1 and 2 shows. However, for this distinction to be conclusive, a side-by-side experiment would need to be conducted, giving a more standardized inoculum between the two experiments. Both Figs. 1 and 2 show the lowest and highest tested severity parameters. The response of mid-level severity was similar to that observed for the low level severities (data not shown). 

Figure 3 shows a comparison of the glucose consumption among a low-severity (Log R0 = 3.3), medium-severity (Log R0 = 4.2), and high-sever-ity (Log R0 = 5.0) pretreatment with and without carbonic acid. Glucose consumption for different severity hydrolysates was measured at the time when the 0% control hydrolysate had achieved 50% utilization. A trend is shown that the yeast was more inhibited as the severity of the pretreatment increased. Figure 3 also shows a difference between corn stover samples and aspen wood samples for the same pretreatments. Aspen wood was more inhibitory than corn stover for all three pretreatment conditions, and the difference between the two continued to increase as the severity of the pretreatment increased. 

The biguanides have a special affinity for the mitochondrial membrane, which causes an alteration in electron transport and results in reduced oxygen consumption. Inhibition of the active transport of glucose in the intestinal mucosa, absent activation of glucose transporters, inhibition of gluconeogenesis, and inhibition of fatty... 

In one of the early studies Cho and Hwang [3.54] studied the integration of continuous fermentation and membrane separation using ethanol selective silicone rubber hollow-fiber membranes. Relative to conventional continuous fermentation, the performance of PVMBR resulted in high yeast cell densities, reduction of ethanol inhibition, longer substrate residence time of, more glucose consumption, and recovery of clean and concentrated ethanol. A 10-20 % increase in ethanol productivity was achieved. Kaseno et al. 

Studies of the carbohydrate metabolism of T. cruzi (21) have shown that phos-phoenolpyruvate serves as the acceptor of the primary COj-fixation reaction. This resulted in the formation of oxaloacetate and malate and the excretion of succinate. The central role of PEPCK in energy metabolism in insect-stage trypanosomatids has been illustrated in the case of T. cruzi epimastigotes, using 3-mercaptopicolinic aeid, a powerful inhibitor of this enzyme (22). Inhibition led to a twofold reduction in the anaerobic production of succinate and a similar decrease in glucose consumption, while the production of alanine, via the transamination of pyruvate, increased threefold. 

Astrup J, Sorensen PM, Sorensen HR. Inhibition of cerebral oxygen and glucose consumption in the dog by hypothermia, pentobarbital, and lidocaine. Anesthesiology. 1981 55 263-268... 

In one study, CHO cells were exposed to chromate, a potent environmental toxin which enters the cytoplasm and interferes with redox enzymes [24]. Ultimately, CHO cells exhibited a rapid and drastic decrease in lactate production, followed by a slower decrease in glucose consumption and acid production. This result could be due to an immediate inhibition of lactate dehydrogenase, halting anaerobic respiration and lowering lactate production, followed by irreversible cell damage which reduced the metabolic rate of glucose consumption and acid production. Preliminary work has also be performed to investigate the metabolic response of cells to pesticides, such as para-thion. The MAMP can be used to probe the metabolic disruption caused by exposure to environmental toxins. 

When a-glucosidase activity is inhibited, carbohydrate digestion is prolonged and takes place further along the intestinal tract. This in turn delays and spreads the period of glucose absorption, which reduces the extent of the postprandial rise in blood glucose concentrations. The effectiveness of a-glucosidase inhibitors is dq en-dent on the consumption of a meal rich in complex carbohydrate. 

Unlike thiabendazole, mebendazole (Vernwx) does not inhibit fumarate reductase. While mebendazole binds to both mammalian and nematode tubuhn, it exhibits a differential affinity for the latter, possibly explaining the selective action of the drug. The selective binding to nematode tubulin may inhibit glucose absorption, leading to glycogen consumption and ATP depletion. 

The Permeable Cell Assay is a simple method to measure the cellular ATP synthetic activity. ATP should be synthesized from domestic ADP and externally added inorganic phosphate mainly by the glycolytic pathway with consumption of glucose. High concentration of inorganic phosphate inhibits luciferase. The used concentration of inorganic phosphate (1.5 mM) was determined that it does not inhibit the activity of luciferase too much. 

The transport system that conveys malate and a-ketoglu-tarate across the inner mitochondrial membrane (see Fig. 19-27) is inhibited by n-butylmalonate. Suppose n-butyl-malonate is added to an aerobic suspension of kidney cells using glucose exclusively as fuel. Predict the effect of this inhibitor on (a) glycolysis, (b) oxygen consumption, (c) lactate formation, and (d) ATP synthesis. 

Administration of KA also produces profound alterations in energy metabolites in the striatum within 2 h of injection (Retz and Coyle, 1982). The depletion in ATP levels may result from either an inhibition of ATP synthesis or an increase in ATP consumption in toxicity induced by KA. Collective evidence suggests that the reduction in glucose levels and concomitant increase in lactate after intrastriatal injections of KA result from an increase in energy consumption during toxicity. It has been proposed that in toxicity induced by KA, ATP depletion to a critical level invariably precedes the onset of cell death (Coyle, 1983). 

---