Rat Liver Phosphoenolpyruvate Carboxykinase Research Articles

Proteomics Analysis Reveals an Important Role for the PPAR Signaling Pathway in DBDCT-Induced Hepatotoxicity Mechanisms.

A patented organotin di-n-butyl-di-(4-chlorobenzohydroxamato)tin (DBDCT) with high a antitumor activity was designed, however, its antitumor and toxic mechanisms have not yet been clearly illustrated. Hepatic proteins of DBDCT-treated rats were identified and analyzed using LC-MS/MS with label-free quantitative technology. In total, 149 differentially expressed proteins were successfully identified. Five protein and mRNA expressions were involved in the peroxisome proliferator-activated receptor (PPAR) signaling pathway, including a scavenger receptor (CD36), adipocyte fatty acid binding protein 4 (FABP4), enoyl-CoA hydratase (EHHADH), acetyl-CoA acyltransferase 1 (ACAA1), and phosphoenolpyruvate carboxykinase (PEPCK) in DBDCT-treated Rat Liver (BRL) cells. PPAR-α and PPAR-λ were also significantly decreased at both protein and mRNA levels. Furthermore, compared with the DBDCT treatment group, a special blocking agent of PPAR-λ T0070907 was used to evaluate the relationship between PPAR-λ and its downstream genes. Our studies indicated that DBDCT may serve as a modulator of PPAR-λ, further up-regulating CD36, FABP4 and EHHADH on the PPAR signal pathway.

In Pursuit of Genes of Glucose Metabolism

If you don't know where you're going, you might wind up someplace else—Yogi Berra My professional journey, once I accepted the fact that I would not play first base for the Chicago Cubs, was not accomplished in a straight line. I entered medical school intending to become a family physician but soon became interested in research. I took an internal medicine residency at the University of California, San Francisco (UCSF), then a long research fellowship in the nascent field of molecular biology at the National Institutes of Health (NIH), and followed that with training in clinical endocrinology at the University of Wisconsin. I spent the next fifteen years dividing my time between the clinic and laboratory at the University of Iowa. Finally, I decided to concentrate on research and spent the next twenty-three years at Vanderbilt University. For the past eleven years, I have been at the University of Iowa, where I helped establish a new diabetes research center. My research journey also had several different directions. Upon reflection, I guess I ended up “someplace else” by choice, and it certainly has been an interesting trip. It is one I unreservedly recommend.

Effect of age on the expression of phosphoenolpyruvate carboxykinase in rat liver.

The effect of age on the expression of phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32) was studied using hepatocytes isolated from 6-, 15-, and 26-mo-old-male Fischer 344 rats fasted for 12 h. The activity of PEPCK in hepatocyte extracts decreased 40-50% (P < 0.05) between 6 and 26 mo of age. The age-related decrease in PEPCK activity was paralleled by a similar decrease (P < 0.05) in the level of PEPCK mRNA. Thus the decrease in PEPCK activity appears to arise from a decrease in level of the PEPCK transcript available for translation. The stability, i.e., half-life of PEPCK mRNA in hepatocytes isolated from 6- and 26-mo-old rats was similar; however, the nuclear transcription of PEPCK by hepatocytes isolated from 26-mo-old rats was 44% lower (P < 0.05) than the nuclear transcription of PEPCK by hepatocytes isolated from 6-mo-old rats. Thus the age-related decline in PEPCK mRNA levels in the liver of fasted rats appears to arise from a decrease in the transcription of PEPCK. A significant decrease (P < 0.05) in the activity and mRNA level of PEPCK also was observed with age in kidney tissue isolated from rats fasted for 12 h.

Immunogold electron microscopic localization of phosphoenolpyruvate carboxykinase in rat liver

Phosphoenolpyruvate carboxykinase (PEPCK) is a rate-limiting gluconeogenic enzyme which catalyzes the conversion of oxaloacetate to phosphoenolpyruvate. A gradient of PEPCK from periportal hepatocytes to pericentral hepatocytes has been demonstrated in normal rat liver; however, the subcellular distribution of PEPCK molecules within hepatocytes could not be determined from these light microscope studies.We have used two immunogold histochemical approaches to study the subcellar distribution of PEPCK in normal rat hepatocytes. In the first procedure 10μm cyrosections of 4% paraformaldehyde perfusion-fixed rat liver were collected on silanated slides and immunostained with goat anti-rat PEPCK (normal goat serum served as a control), and incubated in a secondary antibody (5nm gold-labeled rabbit anti-goat IgG) and a tertiary antibody (5nm gold-labeled goat anti-rabbit IgG). The immunogold stained samples, with or without silver enhancement (IGSS), were counterstained with pyronine Y, re-embedded in Visio- Bond and removed from the slides and semithin sectioned for epipolarized illumination combined with transmitted light microscopy (Figs. 1 and 2), or re-embedded in epoxy resin and sectioned for electron microscopy (EM, Fig. 4) In the second procedure 25, 50 and 100 μm free-floating vibratome sections of well fixed rat liver (4% paraformaldehyde plus 0.5% glutaraldehydeperfusion-fixed, immersion fixed overnight at 4°C) were immunogold stained using a 5nm gold labeled secondary antibody, with and without IGSS, osmicated, embedded in epoxy resin and sectioned for EM (Figure 3).

Immunogold-silver staining and epipolarized light microscopic detection of phosphoenolpyruvate carboxykinase and glycogen phosphorylase in rat liver.

The subcellular distribution of enzymes related to carbohydrate metabolism was determined in sections of paraformaldehyde fixed and polyethylene glycol-1540-embedded rat liver and in cryostat sections. For this purpose, goat anti-rat phosphoenolpyruvate carboxykinase (PEPCK) serum and rabbit anti-rat glycogen phosphorylase (GP) serum were used as primary antibodies to localize the corresponding antigens. The primary antibodies were localized by 5 nm colloidal gold labeled secondary antibodies (either rabbit anti-goat IgG for PEPCK or goat anti-rabbit IgG for GP), and the gold particles were enhanced by silver staining using appropriate development reagents. The silver enhanced gold particles were detected by epipolarized light microscopy. PEPCK and GP immunoreactive molecules were found only in glycogen-containing areas of the cytosome of hepatocytes, and not in other cells. No immunocytochemical staining of hepatocytes was found when normal serum replaced the primary antibody in the procedures. Visio-Bond semithin (0.35-1.0 micron) sections provided higher resolution for subcellular immunostaining of PEPCK and GP than cryosections of 10 microns. Epipolarized light microscopy provided detection at high sensitivity of the gold-labeled antibody, and combined with transmitted light, allowed simultaneous visualization of the tissue morphology.

Physiological concentrations of 2-oxoglutarate regulate the activity of phosphoenolpyruvate carboxykinase in liver.

2-Oxoglutarate was found to inhibit purified rat liver phosphoenolpyruvate carboxykinase when the assay was performed in the direction of either phosphoenolpyruvate or oxaloacetate synthesis. The inhibition was competitive with respect to oxaloacetate or phosphoenolpyruvate, the Ki values being 0.32 +/- 0.04 mM 0.63 +/- 0.19 mM respectively. 2-Oxoglutarate inhibited non-competitively when tested against GTP or Mn2+. The reported cytosolic concentrations of 2-oxoglutarate in rat hepatocytes are such that the enzyme is likely to be significantly inhibited under basal conditions. The cytosolic concentration of 2-oxoglutarate is known to fall precipitously under the influence of glucagon and other hormones that stimulate gluconeogenesis, and it is suggested that the hormone-induced decrease in 2-oxoglutarate content would alleviate the inhibition of phosphoenolpyruvate carboxykinase and stimulate flux from oxaloacetate to phosphoenolpyruvate. The implications of this finding to the rationalization of the role of pyruvate kinase in the stimulation of gluconeogenesis in the fasted state are discussed.

Fluorescent labeling of the nucleotide site in cytosolic rat liver phosphoenolpyruvate carboxykinase

Reaction of rat liver phosphoenolpyruvate carboxykinase (GTP: oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32) with the alkylating fluorescent probe N-(iodoacetylaminoethyl)-5-naphthylamine-1-sulfonic acid (1,5-I-AEDANS), results in complete loss of enzymatic activity. One mole of the fluorescent reagent is incorporated per mole of the inactivated enzyme. When the modification is carried out in the presence of GDPMn, the enzyme retains 97% of its activity with almost no incorporation of label. The specificity of the reaction is further supported by the detection of a unique fluorescent peptide from the trypsin-treated modified enzyme. Fluorescence emission of enzyme-bound AEDANS shows a broad band centered at 470 nm and presents a monoexponential decay with a lifetime of 19 ns. These data indicate that the probe-binding site is considerably less polar than water and similar in polarity to ethanol. Anisotropy determinations give evidence for restricted rotational freedom for AEDANS bound to the rat carboxykinase, while acrylamide quenching studies reveal limited accessibility to the probe site. The results are consistent with specific labeling of rat liver phosphoenolpyruvate carboxykinase at or near the GDP site. The characteristics of the nucleotide-binding sites of rat liver and yeast (ATP) phosphoenolpyruvate carboxykinase are compared.

Inhibition of phosphoenolpyruvate carboxykinase by 6-phosphogluconate in rat liver

Various concentrations of 6-phosphogluconate inhibit rat liver phosphoenolpyruvate carboxykinase activity. 0.04 mM 6-phosphogluconate, which is the concentration found in vivo, caused a 50% inhibition of 6-phosphoenolpyruvate carboxykinase activity. 6-Phosphogluconate lowered the Vmax of the enzyme and increased the concentration of phosphoenolpyruvate required to achieve one-half of the maximum velocity. The role of 6-phosphogluconate as a regulator of the coordination of fluxes through three metabolic pathways is discussed.

The Heterotopic Effects of Insulin and Glucagon on the Acinar Activity Pattern of Phosphoenolpyruvate Carboxykinase in Male and Female Rat Liver

The effects of the administration of insulin and glucagon on the intraacinar heterotopy of phosphoenolpyruvate carboxykinase (PEPCK) were investigated in male and female rat liver. Insulin did not noticeably influence PEPCK activity or its acinar distribution, either in males or in females. But it affected the activities of glucose-6-phosphate dehydrogenase and malic enzyme. Glucagon in supraphysiological concentrations led to an induction of PEPCK activity. Despite high glucagon concentration along the whole sinusoidal length, the inducing effect of glucagon was most pronounced in the periportal and intermediary parts of the acinus; thus indicating that there is no direct interrelationship between local glucagon concentration and PEPCK activity. In both experiments blood glucose levels were kept fairly constant.

Thyroid hormone regulates transcription of the gene for cytosolic phosphoenolpyruvate carboxykinase (GTP) in rat liver

Using an in vitro assay with isolated rat nuclei, we have determined that thyroid hormone causes a 4-6-fold increase in the synthesis of mRNA coding for phosphoenolpyruvate carboxykinase. Proportional changes were seen in the steady-state cytosolic mRNA levels for phosphoenolpyruvate carboxykinase. Dibutyryladenosine cyclic 3',5'-monophosphate, which stimulates transcription of the phosphoenolpyruvate carboxykinase gene in normal rats, remained effective in hypo- or hyperthyroid animals. The effect of epinephrine on transcription of the gene for phosphoenolpyruvate carboxykinase appears to be modulated by thyroid hormone.

3,5,3'-Triiodothyronine-induced synthesis of rat liver phosphoenolpyruvate carboxykinase.

Recent studies have indicated that the starvation induced increase in hepatic phosphoenolpyruvate carboxykinase (PEPck; EC 4.1.1.32) is accelerated in hyperthyroid animals, whereas enzyme degradation is unaffected by the thyroid state. Therefore, the present study was undertaken to investigate the possible direct effect of T3 on the synthesis of this important gluconeogenic regulatory enzyme in vivo and in the isolated perfused liver. T3 injection in hypothyroid animals stimulated PEPck synthesis within 6-12 h. The effect, being dose dependent and significant for 0.1 microgram T3/100 g BW, could be demonstrated in animals fasted or fed a carbohydrate-rich diet. Although varying in the basal rate of synthesis, the T3-induced increase in PEPck synthesis was similar in intact, thyroidectomized, adrenalectomized, and hypophysectomized animals. No additive effect with glucocorticoids was observed, suggesting that endogenous glucocorticoids are not necessary for the hormone action. The T3-induced effect on PEPck synthesis was not mediated by alterations in the endogenous cAMP level, as was indicated (1) by the different time course of PEPck induction via (Bu)2cAMP or T3, and 2) by the finding that T3 was effective also in diabetic animals, despite maximally enhanced tissue cAMP levels. In these animals insulin antagonized the T3 action on the enzyme. T3-mediated PEPck synthesis was not prevented by propranolol. Conversely, an additive effect with isoproterenol on enzyme activity was observed. T3 (1 nM) added to the isolated liver of hypothyroid rats perfused with the synthetic fluorocarbon medium supplemented with 10% iodothyronine free serum, stimulated incorporation of labeled leucine into PEPck protein within a 6-h perfusion time. Taken together, our data demonstrate that T3 at a physiological dose stimulates hepatic PEPck synthesis.

Inhibition of phosphoenolpyruvate carboxykinase by streptonigrin

Streptonigrin, an antibiotic with antineoplastic activity, inhibited rat liver phosphoenolpyruvate carboxykinase with an I 50 of 0.3 μM when excess FeCl 2 was present. No inhibition occurred in the absence of added metal ion. Inhibition was partial and noncompetitive versus ITP and oxalacetic acid. The enzyme was more susceptible to inhibition by Streptonigrin in the absence of substrates. Fe 2+ supported inhibition by Streptonigrin to a greater extent than did Fe 3+, while Mn 2+ activated the enzyme in the presence of Streptonigrin. For maximum inhibition, at least a 3-fold molar excess of iron over Streptonigrin was required. The methyl ester of Streptonigrin was also an inhibitor (I 50 = 4 μM) while the fragment containing the C and D rings was not, indicating that inhibition did not depend solely on the presence of the picolinic acid moiety. When oxalacetate synthesis was measured, Streptonigrin plus iron had no more effect on enzymatic activity than iron alone, and Mn 2+ was capable of stimulating the streptonigrin-Fe 2+ inhibited enzyme.

N6,O2'-dibutyryl cycle AMP and glucose regulate the amount of messenger RNA coding for hepatic phosphoenolpyruvate carboxykinase (GTP).

Rat liver phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.1.32) mRNA was purified to 25% of total mRNA activity (greater than 50-fold enrichment) by polysome immunoprecipitation. This preparation was used as template for the synthesis of cDNA that was subsequently cloned in Escherichia coli. The resulting clones were screened by in situ hybridization and by hybrid-selected translation of phosphoenolpyruvate carboxykinase mRNA. The cDNA insert of one plasmid, pPC2, was complementary to phosphoenolpyruvate carboxykinase mRNA as determined by these screening procedures. pPC2 cDNA was 760 base pairs in length and a partial restriction enzyme map was constructed. pPC2 was labeled with 32P by nick translation and was used as a hybridization probe to quantitate phosphoenolpyruvate carboxykinase mRNA following N6,O2'-dibutyryl cAMP (Bt2cAMP) injection or glucose feeding. Bt2cAMP increased whereas glucose decreased the level of hybridizable phosphoenolpyruvate carboxykinase mRNA and in all cases the changes were proportional to the in vitro translational activities measured in a reticulocyte lysate system. The half-life of phosphoenolpyruvate carboxykinase mRNA sequences was measured by an indirect procedure involving their quantitation, by hybridization assay, during deinduction and induction. The half-life was approximately 10-40 min during deinduction by glucose or during induction stimulated by Bt2cAMP. Our data indicate that cAMP enhances some step in the generation of phosphoenolpyruvate carboxykinase mRNA.

Rate of synthesis and degradation of rat liver phosphoenolpyruvate carboxykinase in the different thyroid states

The effect of hypo-, eu-, and hyperthyroidism on the relative rate of rat liver phosphoenolpyruvate carboxykinase (PEP-ck) synthesis and degradation was studied in vivo by a radioimmunological technique. In hypo- and euthyroid rats, starvation induced an identical increase in PEP-ck synthesis and activity. Hyperthyroidism led to a significant acceleration in enzyme synthesis and correspondingly enhanced enzyme levels. PEP-ck degradation rate, as measured by the double pulse-labeling technique, was not affected by different thyroid states in starved rats ( t 1 2 ~ 8 h ). Hypo-, eu-, and hyperthyroid starved rats responded to glucose refeeding with a rapid and similar PEP-ck deinduction, followed by a concomitant decrease in enzyme activity.

Regulation of rat liver phosphoenolpyruvate carboxykinase (GTP) messenger ribonucleic acid activity by N6, O2'-dibutyryladenosine 3',5'-phosphate.

N6,O2'-Dibutyryladenosine 3',5'-phosphate (Bt2cAMP) induces the synthesis of the gluconeogenic enzyme, phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.32), in rat liver by increasing the activity of messenger ribonucleic acid (mRNA) coding for this enzyme (mRNAPEPCK) more than 20-fold (from less than 0.01% to greater than 0.20% of total mRNA activity) as determined by using in vitro translation systems which measure only active mRNAPEPCK. The increase in mRNAPEPCK activity could result from increased synthesis, increased processing, or decreased inactivation rates. Actinomycin D and cordycepin inhibit mRNAPEPCK induction by 89% and 70%, respectively, a result that indicates a requirement for ongoing RNA synthesis but that does not distinguish which of these steps is regulated by cAMP. We have employed a kinetic approach, not involving RNA synthesis inhibitors, to determine the half-life of mRNAPEPCK both during a period of deinduction following glucose feeding and during a subsequent induction by Bt2cAMP. An estimated half-life of 20 +/-5 min during both of these periods indicates that Bt2cAMP has no effect on the rate of inactivation of mRNAPEPCK. We conclude that Bt2cAMP effects the increase in activity of mRNAPEPCK by promoting its synthesis or processing.

Rapid inactivation of rat liver phospho enolpyruvate carboxykinase by microsomes and reversal by reductants

The hepatic gluconeogenic enzyme phospho enolpyruvate carboxykinase (GTP:oxaloacetate carboxy-lase (transphosphorylating), EC 4.1.1.32) is activated 3–4-fold by micromolar quantities of Fe 2+ and ferroactivator, a cytosol protein that is necessary for this activation. After the carboxykinase in liver cytosol, or the purified carboxykinase, was activated by adding Fe 2+, rat liver microsomes were added to duplicate their ratio to the carboxykinase in liver. Microsomes caused a biphasic inactivation of the carboxykinase in cytosol. All of the activity corresponding to Fe 2+ activation was lost within 10 min ( t 1 2 equaled 3–4 min) and the remaining (basal) activity was lost over hours ( t 1 2 equaled 3–4 h). Adding the reducing agent dithiothreitol (1 mM) after 10 or 60 min of exposure of cytosol to microsomes caused a complete and three-fourths complete restoration of Fe 2+ activation. In preventing the microsome-induced loss of Fe 2+ activation, ascorbate and cysteine were also effective. When the purified carboxykinase was activated by Fe 2+ and the synthetic ferroactivator 3-aminopicolinate, microsomes interfered with the enzyme activity in a manner identical to their effect on the enzyme in cytosol, suggesting that they did not act on ferroactivator protein. When Fe 2+ was added to the crude or the purified carboxykinase 5–60 min after microsomes, the carboxykinase was not activated. If the microsomes were acting by oxidizing or sequestering Fe 2+, the carboxykinase would have been at least transiently activated because it takes only seconds for Fe 2+ to fully activate the enzyme and minutes for microsomes to cause a complete loss of Fe 2+ activation. By the process of elimination, microsomes probably act on the carboxykinase itself. Microsomes did not inactivate five other glycolytic/gluconeogenic enzymes in liver cytosol, including some that have sulfhydryls which are very sensitive to oxidation. The microsomal factor was inactivated by the proteases, chymotrypsin, trypsin and pronase. The activity of the microsomal factor was highest in liver and kidney; almost as high in heart as in liver; and low or negligible in pancreas, spleen, lung and skeletal muscle. The microsomal activity was decreased in livers of alloxan diabetic rats, and the decrease was proportional to their blood glucose concentrations — such that severely diabetic rats had almost none of the activity. Liver microsomes from rats treated with the antioxidant, vitamin E, were completely without effect on Fe 2+ activation. The results indicate that it is possible to alter rapidly the Fe 2+ activation of phospho enolpyruvate carboxykinase by mechahisms that probably involve oxidation/reduction. The decreases in the microsomal factor induced by alloxan diabetes; its high content in the gluconeogenic organs, liver and kidney; and its apparent specificity for the carboxykinase are preliminary evidence of the microsomal factor having a physiological role in the regulation of the carboxykinase.

Degradation of extracellular protein by the isolated perfused rat liver: A biochemical and autoradiographic study

The isolated perfused rat liver was used to study the degradation of 125I-labelled protein supplied in the perfusion medium. Formaldehyde-denatured proteins (human serum albumin, bovine serum albumin and especially rat liver phosphoenolpyruvate carboxykinase (GTP)) were taken up by the liver and degraded at high rates. Native human serum albumin was not degraded at significant rates by the perfused liver, while native phosphoenolpyruvate carboxykinase (GTP) was catabolised at about one-fourth the rate of the denatured enzyme. The degradation rate of denatured human serum albumin increased markedly as protein was added up to 0.7 mg, and more gradually with further increases in added protein. The biphasic nature of concentration dependence probably reflects the contribution of different cell types in the liver. Autoradiographic examination of serial biopsies taken during perfusion of the liver with formaldehyde-denatured, 125I-labelled bovine serum albumin showed that at the cellular level the radioactivity was located predominantly in Kupffer and other non-parenchymal cells; and at the subcellular level the radioactivity was largely in endocytic vesicles, lysosomes and occasionally in the sinusoidal spaces. No significant radioactivity was found associated with other cytoplasmic organelles or the nucleus. It is concluded that lysosomes of the non-parenchymal cells are primarily responsible for the degradation of denatured extracellular protein that enters the liver.

Schedule of Protein Ingestion and Circadian Variations of Glycogen Phosphorylase, Glycogen Synthetase and Phosphoenolpyruvate Carboxykinase in Rat Liver

The circadian rhythms of liver glycogen and hepatic activity of glycogen synthetase (GS), glycogen phosphorylase (GP) and phosphoenolpyruvate carboxykinase (PEPCK) were studied in adult male rats. The rats either received a mixed diet ad libitum (10% protein) or a protein meal (1.85 g protein) given at 09:00 or 21:00 hours, with free access to a protein-free diet (separately-fed). When the protein meal was ingested at 09:00 hours it was followed by a drop in liver glycogen and a persistent daylight increase in GP and PEPCK activities, this phenomenon being attenuated when proteins were ingested during darkness (21:00 hours). Moreover in the latter case, the circadian rhythm of liver glycogen was modified (glycogen accumulation occurring later) and the protein meal ingestion was followed after a transient decrease by a high and sustained GS activity during a long period (12 hours). The drop in the hepatic glycogen level and the unusually long daylight period of sustained GP and PEPCK activities in separately-fed rats consuming the protein meal at 09:00 hours suggests that, in this case, part of the ingested nitrogen could have been catabolized and used for gluconeogenesis, thus explaining our previous observation of lower nitrogen retention observed in this group of rats.

Induction of rat liver phospho enolpyruvate carboxykinase (GTP) by cyclic AMP during starvation. The permissive action of glucocorticoids

The effect of starvation on the activity of hepatic phospho enolpyruvate carboxykinase (GTP: oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32), and on the response of the enzyme to N 6- O 2′-dibutyryl adenosine 3′,5′-monophosphate was investigated in intact and glucocorticoid-deprived rats. In the liver of intact animals, starvation produced a rapid increase in the concentration of cyclic AMP and a corresponding increase in the activity of phospho enolpyruvate carboxykinase. The kinetics of both changes were not affected by adrenalectomy. Injection of N 6- O 2′-dibutyryl adenosine 3′, 5′-monophosphate into intact starved rats resulted in an immediate, dramatic increase in phospho enolpyruvate carboxykinase activity above the starvation level. Adrenalectomy completely blocked the response of the enzyme to the cyclic nucleotide. Restoration of hydrocortisone to the adrenalectomized animals restored the full N 6- O 2′-dibutyryl adenosine 3′,5′-monophosphate effect a lag period of 2 h. The physiological significance of these findings is considered. The data are interpreted with regard to the current hypothesis that glucocorticoids promote an increase in translatable phospho enolpyruvate carboxykinase mRNA, while cyclic AMP enhances the translation of preexisting specific mRNA templates.

Inactivation of phosphoenolpyruvate carboxykinase by acetaldehyde

Preincubation with acetaldehyde at 37°C inactivates rat liver phosphoenolpyruvate carboxykinase. The inactivation is dependent upon the acetaldehyde concentration and the pH and duration of preincubation, and is prevented but not reversed by glutathione. The binding of the substrate ITP appears to be affected in the inactivation process. This effect of acetaldehyde might contribute to inhibition of gluconeogenesis resulting from ethanol metabolism.