Pyruvate production

Williams J, Foster PM. 1989. The effects of 1,3-dinitrobenzene and mono-(2-ethylhexyl) phthalate on hormonally stimulated lactate and pyruvate production by rat Sertoli cell cultures. Toxicol Lett 47 249-257. 

Muscle activity involves processes such as aerobic and anaerobic glycolysis and is therefore accompanied by an increased pyruvate production. Consequently, the pyruvate transamination product alanine will be increased after exercise. Heavy exercise may be associated with an increased need of creatine biosynthesis from arginine. Ornithine is a by-product of this pathway and may be increased under these conditions. 

Zelic, B., Gostovic, S., Vuorilehto, K., Vasic-Racki, D., and Takors, R. 2004. Process strategies to enhance pyruvate production with recombinant Escherichia coir. From repetitive fed-batch to in situ product recovery with fully integrated electrodialysis. Biotechnol. Bioeng. 85, 638-646. 

S.C.J. Reader, and R.M.D. Foster, The in vitro effects of four isomers of dinitro-toluene on rat sertoli and sertoli-germ cell co-cultures Germ cell detachment and lactate and pyruvate production. Toxicol. Appl. Pharmacol. 106 287-294, 1990. 

Figure 4 Time courses of glucose consumption and metabolite production during hydrogen production using the strain MC4100 (open circular) and its LDH-A mutant, MC13-4 (close circular). (A) glucose consumption, (B) hydrogen production, (C) lactate production, (D) pyruvate production, (E) formate production, and (F) sum of the produced ethanol and acetate.

This calculation is based on that 2 molecules of hydrogen are produced from 1 molecule of glucose. Amount of gluoose consumed in PFL-LDH is estimated by the sum of the amount lactate production, pyruvate production,acetate production, and ethanol production 204 mmo) in MC4100 and 160 mmol in MC13-4. 

C4 plants possess two types of photosynthesizing cells in their leaves mesophyll cells and bundle sheath cells. (In C3 plants, photosynthesis occurs in mesophyll cells.) Most mesophyll cells in both plant types are positioned so that they are in direct contact with air when the leaf s stomata are open. In C4 plants, C02 is captured in specialized mesophyll cells that incorporate it into oxaloacetate (Figure 13B). Phosphoenolpymvate carboxylase (PEP carboxylase) catalyzes this reaction. Oxaloacetate is then reduced to malate. Once formed, malate diffuses into bundle sheath cells. (As their name implies, bundle sheath cells form a layer around vascular bundles, which contain phloem and xylem vessels.) Within bundle sheath cells, malate is decarboxylated to pyruvate in a reaction that reduces NADP+ to NADPH. The pyruvate product of this latter reaction diffuses back to a mesophyll cell, where it can be reconverted to PEP. Although this reaction is driven by the hydrolysis of one molecule of ATP, there is a net cost of two ATP molecules. An additional ATP molecule is required to convert the AMP product to ADP so that it can be rephos-phorylated during photosynthesis. This circuitous process delivers CO, and NADPH to the chloroplasts of bundle sheath cells, where ribulose-1,5-bisphosphate carboxylase and the other enzymes of the Calvin cycle use them to synthesize triose phosphates. 

Consider for example the pyruvic acid/pyruvate product of glycolysis, which may be written equivalently as... 

The success of pyruvate production from lactate depends also on the stability of pyruvate in the presence of Proteus mirabilis or P. vulgaris cells. In fact the cells degrade pyruvate rather effectively if the enzyme pyruvate formate-lyase (EC 2.3.1.54) is active. Since it is known that for the activation of this enzyme ferrous ions are necessary (64) we blocked the ferrous ions by 5 mM EDTA. Under these conditions pyruvate is stable for more than 100 h (62). 

The model consists of a set of partial differential equations describing the acrylic acid, lactate and pyruvate production, cellular growth, and glucose consumption (see Table 2). 

In skeletal muscle and other tissues, ATP is generated by anaerobic glycolysis when the rate of aerobic respiration is inadequate to meet the rate of ATP utilization. Under these circumstances, the rate of pyruvate production exceeds the cell s capacity to oxidize NADH in the electron transport chain, and hence, to oxidize pyruvate in the TCA cycle. The excess pyruvate is reduced to lactate. Because lactate is an acid, its accumulation affects the muscle and causes pain and swelling. 

It is assumed that both the reactions are catalyzed by the complex of PEP-Pi-enzyme. CO2 competes for the complex, driving the reaction towards oxaloacetate and thus decreasing the rate of pyruvate production. Reaction 3.11 is irreversible under experimental conditions, but reaction 3.10 is reversible and interesting in that PPi can be used to form PEP from pyruvate (Davis and Wood, 1966). Therefore, the PPi derived from ATP can be reutilized, thus acting as a control mechanism for PEP preservation. And since PPi strongly inhibits the PEP carboxytransphosphorylase reaction, PEP can be diverted to the Krebs cycle (Frings and Schlegel, 1970). 

The postulated mechanisms in this case were (a) a concentration-dependent reversible inhibition of neuronal potassium currents, leading to an extracellular shift or (b) inhibition of phosphofructokinase, leading to a reduction in intracellular lactate and pyruvate production and increases in intracellular pH and potassium concentration. Hypokalemia before the administration of thiopental was possibly secondary to treatment with insulin and positive inotropes. The authors recommended that abrupt withdrawal of thiopental should be avoided and that a tapering strategy should be used. 

Carbon for FAS could also be produced via ATP-citrate lyase. This activity, which will convert citrate to oxaloacetate plus acetyl-CoA, has been demonstrated in soybean extracts. But there is no current evidence for citrate transport into the plastid nor of localisation of this activity in the plctstid to support citrate cleaving enzyme as a source of carbon for FAS, at least for avocado mesoccirp plastids. Extracts of developing soybean also contain a NADP+-dependent medic enzyme.20 NAD+-dependent malic enzyme, which produces pyruvate ind Cctrbon dioxide from malate, is an enzyme specific to the mitochondrial matrix in higher pleints.21 The localisation of NADP+-malic enzyme in immature soybeans, eind the possibility of pyruvate production other than by pyruvate kinase, and the utilisation of this pyruvate in FAS, remain to be determined. 

Finally, while NMR studies of PB25 differ in some respects, they all reveal that the mutant has increased Ppc flux. This makes sense from two standpoints. First, the mutation can cause an increase in PEP, the substrate for the Ppc-catalyzed reaction. Second, maintaining flux through the Krebs cycle can be accomplished when pyruvate production is curtailed by increasing the Ppc-catalyzed, anaplerotic reaction PEP - oxaloacetate. 

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