The effect of (+) cyanidanol-3 on the Na+-K+-ATP-ase and Mg++-ATP-ase activities of the rat brain in the presence and absence of ascorbic acid

The authors investigated the effects of (+) cyanidanol-3-(Catergen) in vitro on the activities of rat brain plasma membrane and microsomal Na+-K+-ATP-ase and Mg++-ATP-ase, in the presence and absence of ascorbic acid. Due to lipid peroxidation induced by low concentration of ascorbid acid, activity of both ATP-ase decreased. (+) cyanidanol-3 proved to be an effective antioxidant in this system. It inhibited the decrease of ATP-ase activity which occurred as a result of lipid peroxidation promoted by ascorbic acid.     

Effect of combined anesthetics on the activity of various myocardium enzymes

It is demonstrated by experiments with rabbits that the Ca2+-ATP-ase activity is stabilized when using combined anesthetics (diacetylcholine + halothane + N2O) as distinct from application of halothane. A decrease in the cholinesterase activity is less pronounced than under the halothane action but more than with the diacetylcholine application. A decrease in the Na+, K+-ATP-ase activity is observed with all types of anesthesia. A considerable inhibition of creatine kinase under the action of combined anesthesia and halothane and an increase of the lactate dehydrogenase activity under diacetylcholine application in mitochondria are shown. Reliable differences in the succinic dehydrogenase activity are not detected.     

Activity of Ca(+2)Mg(+2) --ATPase in erythrocyte membranes of women with diabetes mellitus type I]

The activity of Ca(++)-Mg++ ATP-ase present in erythrocyte membranes was determined in basal conditions and following stimulation with calmodulin in 8 women with insulin-dependent diabetes and in 9 healthy women. The isolation of erythrocyte membranes and the determination of activity of Ca(++)-Mg(++)-ATP-ase were carried out according to the method of Gietzen et al. A decrease in the activity of Ca(++)-Mg(++)-ATP-ase in basal conditions was found in fractions with the highest erythrocyte content obtained from diabetic patients. After stimulation with calmodulin the activity of Ca(++)-Mg(++)-ATP-ase in all the fractions was lower in diabetic patients than in the controls. Low activities of the enzyme were accompanied by high values of HbA1c. The results suggest that glycosylation of the ATP-ase or/and calmodulin may be the main cause of the observed fall in the enzyme activity in diabetes. Also the disturbances concerning the cumulation of intracellular calcium may be related to the changes caused by glycosylation of Ca(++)-Mg(++)-ATP-ase or/and calmodulin.     

Creatine kinase and ATPase in human seminal fluid and prostatic fluid

A creatine kinase assay based on estimation of creatine liberated from creatine phosphate was accurate and reproducible for use with seminal or prostatic fluid, after allowance was made for acid phosphatase interference. Comparison of this method with one which relies on enzymic coupling of ATP formation to NADP+ oxidation shows that the latter under-estimates creatine kinase activity by a factor of about 3. This discrepancy could be due to the high ATPase activity found in prostatic and seminal fluid. Uncritical use of the NADP+ assay might account for different seminal creatine kinase values reported in the literature. Interrelationships between ATPase, creatine kinase and zinc suggest that seminal ATPase is a prostatic secretory product while creatine kinase may be multiglandular in origin.     

Effect of magnesium ions on Ca2+, Mg2+-ATPase on plasma membranes of thymocytes]

Ca2+, Mg(2+)-ATP-ase of plasmatic membranes of thymocites were studied as affected by Mg ions. A complex character of the reaction rate dependence on Mg2+ concentration in the range of 0.002-25. OmM was revealed. The data obtained indicate the existence of Mg(2+)-binding centre of ATP-ase which regulates the enzyme catalytic activity.     

Phosphatase activity in the myenteric plexus

Intense and very intense reactions were obtained for acid phosphatase, calcium activated ATP-ase (pH 9.4), magnesium activated ATP-ase (pH 7.2) and glucose-6-phosphatase in the cytoplasms of the myenteric plexus nerve cells of the small intestine of Macacus rhesus and rabbit. Nucleotidase activity was moderate or slight and unspecific alkaline phosphatase activity absent. Both ATP-ases presented an intense activity in the myenteric plexus nerve cells of human fetuses 30, 33, and 34 weeks old; 5-nucleotidase activity, slight in the 30-week-old fetuses became more intense in the 33- and 34-week-old fetuses. The satellite neuroglial cells, nerve fibers and blood capillaries presented negative alkaline phosphatase reactions and intense or very intense activities of the other phosphatases.     

Differential effects of calcium ion concentration on cell fusion,cell division and creatine kinase activity in muscle cell cultures

Cell fusion, cell number, soluble cell protein and creatine kinase activity have been measured simultaneously in chick muscle cell cultures exposed to various calcium ion concentrations for various periods of time, by adding either extra calcium chloride or the calcium-chelating agent, EGTA. Up to 0.75 mM EGTA cell fusion is not inhibited, but the specific activity of creatine kinase is reduced by 20–50%. Between 0.75 and 1.7 mM EGTA, cell fusion is gradually abolished and the increase in cell number prevented, but enzyme specific activity actually increases again and returns to control values. Adding extra Ca²⁺ produces small increases in cell fusion and soluble cell protein, but much greater increases in creatine kinase activity. EGTA stimulates thymidine incorporation into DNA at low concentrations and then inhibits again as its concentration is increased further. These effects of EGTA on cell division may be related to its effects on creatine kinase. The implications of these results are discussed in terms of current ideas about the inter-relationships between cell fusion, cell division and the accumulation of muscle proteins during differentiation. In particular they show that cell fusion is not essential for the attainment of normal levels of creatine kinase.     

Caracterisation d'une ATP-ase membranaire en presence d'une phosphatase acide dans les lutoïdes du latex d'Hevea brasiliensis

Latex lutoids constitute a polydispersed vacuole with lysosomal character. Lutoids possess a membrane which retains ATP-ase and acid phosphatase activity. Acid phosphatase may be inhibited by ammonium molybdate or phosphate, making it possible to characterize an ATP-ase with an optimum pH of between 7·5 and 8·0. This ATP-ase is Mg²⁺ dependent, does not require K⁺ specifically but is affected by the ionic concentration of the medium.     

Association of microcystin-LR and its biotransformation product with a hepatic-cytosolic protein.

Microcystin-LR (MCYST-LR), a cyclic peptide hepatotoxin, associates with high-molecular-weight, liver cytosolic components. Repetitive cycles of heat denaturation and pronase digestion released 80 +/- 6% of the bound radiolabel from these components, parent toxin (22%), and two biotransformation products, with high-performance liquid chromatography (HPLC) retention times of 6.7 (52%) and 5.6 (13%) min. Both parent and the biotransformed (6.7 min) toxin appeared to be covalently bound to a monomeric protein of molecular weight 40,000 (protein plus radiolabeled toxin). Binding and biotransformation reactions were time- and temperature-dependent and did not require endogenous molecules less than 6,000 daltons. The binding appeared to be saturable with a maximum of 20 pmol MCYST-LR bound per mg protein. The binding protein(s) and biotransformation activity were present in rat liver, brain, kidney, heart, lung, small intestine, large intestine, testes, skeletal muscle, and to a lesser extent, in fat. Okadaic acid, a specific protein phosphatase inhibitor, showed a concentration-dependent inhibition of [3H]MCYST-LR binding to hepatic cytosol. The molecular weight and organ distribution of the binding protein(s), and inhibition of binding by okadaic acid were consistent with one of the binding sites being the catalytic subunit of protein phosphatase type 2A.     

Activity of various enzymes of energy metabolism in the rat kidney and intestines in vitamin D and K deficiency

The vitamin D and K deficiency was studied for its effect on creatine kinase, phosphorylase and alkaline phosphatase activity of rat kidneys and intestinal mucosa. The results show that creatine kinase and phosphorylase activity of kidneys varies depending on the content of these vitamins, e.g. it is activated with vitamin D depletion irrespective of the vitamin K status and remains unchanged with the deficiency of vitamin K alone. In this case the vitamin D deficiency affects kidney phosphorylase and intestinal mucosa differently. Data obtained and those available in literature permit suggesting that the deficiency of the same vitamin may exert a different action on the activity of isoforms of such enzymes as creatine kinase and phosphorylase.     

Changes of enzyme activity in the rat liver at different age in circadian cycle

Most of the biological processes in the living organisms of both animals and man are known to be of rhythmical nature. Variability of enzymatic activity in circadian cycle depends on many factors among other on age, sexual maturity, diet as well as medication. The results obtained in our studies indicate, that the activity changes of acid phosphatase and ATP-ase Mg++ dependent in the liver of all the examined age groups were of 24 hour circadian rythm. As to the acid phosphatase activity the results of this experiments showed that in circadian cycle in all examined age groups there is only one peak of elevated activity. ATP-ase Mg++ dependent showed two activity peaks appearing at the same hour both in 30 and 60 days old animals. It should be noticed that the activities of ATP-ase Mg++ dependent in 100 day old animals were two times higher than in 30 and 60 days old rats.     

Association of microcystin-LR and its biotransformation product with a hepatic-cytosolic protein

Microcystin-LR (MCYST-LR), a cyclic peptide hepatotoxin, associates with high-molecular-weight, liver cytosolic components. Repetitive cycles of heat denaturation and pronase digestion released 80 ± 6% of the bound radiolabel from these components, parent toxin (22%), and two biotransformation products, with high-performance liquid chromatography (HPLC) retention times of 6.7 (52%) and 5.6 (13%) min. Both parent and the biotransformed (6.7 min) toxin appeared to be covalently bound to a monomeric protein of molecular weight 40,000 (protein plus radiolabeled toxin). Binding and biotransformation reactions were time- and temperature-dependent and did not require endogenous molecules <6,000 daltons. The binding appeared to be saturable with a maximum of 20 pmol MCYST-LR bound per mg protein. The binding protein(s) and biotransformation activity were present in rat liver, brain, kidney, heart, lung, small intestine, large intestine, testes, skeletal muscle, and to a lesser extent, in fat. Okadaic acid, a specific protein phosphatase inhibitor, showed a concentration-dependent inhibition of [³H]MCYST-LR binding to hepatic cytosol. The molecular weight and organ distribution of the binding protein(s), and inhibition of binding by okadaic acid were consistent with one of the binding sites being the catalytic subunit of protein phosphatase type 2A.     

Ultracytochemical study of ATP-ase activity in mucosal parietal cells and in the cells of human adenocarcinoma of the stomach]

Ultracytochemical investigation of ATP-ase activity was carried out in parietal cells of the mucosa and in cancer cells of human stomach carcinoma possessing a similar ultrastructure. In parietal cells the reaction product of ATP-ase was observed on the membranes of microvilli of intracellular canaliculi, on the membranes delineating the lateral intercellular space, on the basal plasmolemma and in the nucleoli. The reaction product was absent on the membranes of tubuvesicles and on the apical surface of the plasmalemma. In cancer cells the reaction product was found on the membranes of the microvilli of the intracellular canaliculi, basal plasmolemma and in the nucleoli. Comparative examination of ATP-ase activity in these cells implies that at least the part of the mechanism of hydrochloric acid secretion which is involved in the transfer of H+ and Cl- is retained in cancer cells. A steady decrease in hydrochlorid acid secretion observed in the stomach mucosa in cancer as well as in the tumour itself seems to be associated with other mechanisms.     

Characteristics of magnesium-dependent, Ca2+ -stimulated endogenous protein kinase-catalyzed phosphorylation of basic proteins in myelin isolated from rat brain stem white matter

Purified myelin fraction isolated from rat brain white matter contained Mg²⁺-dependent protein kinase capable of phosphorylation of myelin basic proteins. The Mg²⁺-supported kinase was markedly stimulated (two- to fivefold) by micromolar concentrations of free Ca²⁺ with and without Triton X-100 in the assay, the degree of stimulation being greater with the detergent present. Cyclic AMP, on the other hand, failed to show any effect on phosphorylation of myelin in the absence of Triton X-100 and in the presence of Triton caused only 25–30% stimulation. The phosphorylation reaction was temperature dependent and exhibited a pH optimum at pH 6.5. Apparent affinity toward MgATP^2? was found to be about 70 μm and Ca²⁺ had no effect on this parameter. Dependence on MgCl₂ of myelin phosphorylation indicated the presence of high- and low-affinity sites toward Mg²⁺; Ca²⁺ appeared to influence the low-affinity site. Maximal level of phosphorylation was attained by 10–15 min at 30 °C and it declined at longer incubation times due to phosphatase activity present in the preparation. Stimulatory effect of Ca²⁺ on phosphorylation was not due to inhibition of phosphatase activity. Dephosphorylation experiments showed that neither cyclic AMP nor Ca²⁺ influenced the myelin phosphatase activity. Autoradiographic analysis revealed that phosphorylation of myelin basic proteins accounted for nearly 90% of total myelin phosphorylation. This was supported by the observation that the HCl extract of myelin contained 85% of total activity and comigrated with purified myelin basic proteins. Basal and Ca²⁺-stimulated phosphorylation of basic proteins were due to phosphorylation of serines mainly, although threonine was phosphorylated to a minor extent. Within myelin, Ca²⁺ and cyclic AMP kinases are differentially bound. It appears that the myelin kinase (studied in vitro) is primarily influenced by Ca²⁺ rather than cyclic AMP. Inhibitors (Type I and Type II) of cyclic nucleotide-stimulated protein kinases had no effect on the Ca²⁺-stimulated phosphorylation although basal and cyclic AMP-stimulated phosphorylation was inhibited, indicating that the Ca²⁺ kinase is a separate and distinct enzyme from the cyclic AMP-stimulated and basal kinase(s). Also, leupeptin, a protease inhibitor, did not influence basal, cyclic AMP-stimulated, or Ca²⁺-stimulated myelin phosphorylation, indicating that under the conditions used protease(s) did not alter the myelin kinase activity. The potential significance of phosphorylation of myelin basic proteins and the stimulatory action of Ca²⁺ on this reaction are discussed.     

Modification of contractile proteins by oxygen free radicals in rat heart

This study was undertaken to investigate the effects of oxygen free radicals on myofibrillar creatine kinase activity. Isolated rat heart myofibrils were incubated with xanthine+xanthine oxidase (a superoxide anion radical-generating system) or hydrogen peroxide and assayed for creatine kinase activity. To clarify the involvement of changes in sulfhydryl groups in causing alterations in myofibrillar creatine kinase activity, 1) effects of N-ethylmaleimide (sulfhydryl groups reagent) on myofibrillar creatine kinase activity, 2) effect of oxygen free radicals on myofibrillar sulfhydryl groups content, and 3) protective effects of dithiothreitol (sulfhydryl groups-reducing agent) on the changes in myofibrillar creatine kinase activity due to oxygen free radicals were also studied. Xanthine+xanthine oxidase inhibited creatine kinase activity both in a time-and a concentration-dependent manner. Superoxide dismutase (SOD) showed a protective effect on the depression in creatine kinase activity caused by xanthine+xanthine oxidase. Hydrogen peroxide inhibited creatine kinase activity in a concentration-dependent manner; this inhibition was prevented by the addition of catalase. N-ethylmaleimide reduced creatine kinase activity in a dose-dependent manner. The content of myofibrillar sulfhydryl groups was decreased by xanthine+xanthine oxidase; this reduction was protected by SOD. Furthermore, the depression in myofibrillar creatine kinase activity by xanthine+xanthine oxidase was protected by the addition of dithiothreitol. Oxygen free radicals may inhibit myofibrillar creatine kinase activity by modifying sulfhydryl groups in the enzyme protein. The reduction of myofibrillar creatine kinase activity may lead to a disturbance of energy utilization in the heart and may contribute to cardiac dysfunction due to oxygen free radicals.     

The effect of bile salts on oxygen consumption, oxidative phosphorylation and ATP-ase activity of mucosal homogenates from rat jejunum and ileum

The conjugated bile salts, sodium taurocholate and glycocholate, inhibited oxygen consumption and uncoupled oxidative phosphorylation of mucosal homogenates from rat jejunum and ileum. These bile salts also were capable of increasing the ATP-ase activity, in the presence of Na⁺ + K⁺ with Mg⁺⁺, of both mucosal homogenates. Consequently, it was concluded from the results of this investigation that the previously observed decrease in ATP levels of rat jejunum and ileum, in the presence of bile salts, can be accounted for by both a complete uncoupling of oxidative phosphorylation and by an increase in ATP-ase activity. Furthermore, the mechanism of bile salt inhibition of tissue ATP levels was discussed in relation to a regulatory role played by bile salts in the active transport of water soluble substances across the small intestine.     

Noncompetitive, Ca(2+)-independent inhibition of pyruvate dehydrogenase phosphatase by fluphenazine.

The effects of two different classes of calmodulin antagonists on the catalytic activities of purified pyruvate dehydrogenase (PDH) phosphatase and PDH complex (PDC) were studied. In general, PDH phosphatase was more strongly inhibited than PDC by the calmodulin antagonists with the following potency order: fluphenazine > chlorpromazine > thioridazine > triflupromazine. Promazine and two sulfonamides (W-5 and W-7) did not suppress PDH phosphatase activity at 1 mM concentrations, while about 20% of PDC activity was inhibited by these antagonists. Fluphenazine-mediated inhibition of PDH phosphatase was observed with the purified PDC as well as intact mitochondria. Although Ca2+ stimulates PDH phosphatase activity, the addition of exogenous Ca2+ did not overcome the inhibition by calmodulin antagonists. These results suggest that the suppression of PDH phosphatase activity is dependent upon the structure of the individual calmodulin antagonist and appears to be Ca(2+)-independent. Kinetic analysis showed a noncompetitive inhibition of PDH phosphatase by fluphenazine, indicating that it binds to different site(s) from the catalytic site of the enzyme.     

Stimulation of creatine kinase BB activity by 1 alpha,25-dihydroxycholecalciferol and 24R,25-dihydroxycholecalciferol in rat tissues.

Vitamin D metabolites stimulate creatine kinase BB activity in organs of vitamin D-deficient rats. In epiphyses of long bones, creatine kinase BB activity increases 2.6-fold 24 h after injection of 24R,25-dihydroxycholecalciferol but not of 1 alpha,25-dihydroxycholecalciferol. Contrariwise, 1 alpha,25-dihydroxycholecalciferol, but not 24R,25-dihydroxycholecalciferol, increases creatine kinase BB activity in diaphyses and in kidney. Neither metabolite affects creatine kinase activity in duodenal mucosa.     

Electron microscope studies of phosphatases in the small intestine of Rana temporaria during larval development and metamorphosis

Summary Changes in the ultrastructure, and distribution of phosphatases in the intestinal epithelium of Rana temporaria during development were consistent with other developmental changes. Alkaline phosphatase AMP-ase and ATP-ase were always associated with sites of absorption of foodstuffs into the cell. Initially, these were only the yolk platelets but at the onset of feeding the brush border lateral wall, membranes and associated absorption vesicles all became sites of activity. At metamorphosis when the larvae cease feeding, the enzyme activities decreased and became difficult to detect.In the early larval stages, acid phosphatase activity was confined principally to the lateral cell-wall membranes. This soon disappeared but was followed at metamorphosis by a dramatic increase in both the number of sites and their activity. In general, acid phosphatase appeared to be associated with areas of degeneration. The new epithelial cells which developed during metamorphosis appeared under the old epithelium. The cell debris from the larval epithelium was then expelled into the lumen of the intestine. The new epithelium contained sites of enzyme activity similar to those of the adult. Acid phosphatase was now present only in lysosome-like bodies and very sparsely on the brush border.These results are discussed in relation to dietary and structural changes. It is suggested that the presence of the enzymes at any site can be related to and anticipate these changes, possibly under hormonal control.     

Mutations in the charged residues of the amino terminus of rat liver fructose 6-phosphate,2-kinase:Fructose 2,6-bisphosphatase: effects on regulation.

Amino and carboxyl termini of the bifunctional enzyme Fru 6-P, 2-kinase:Fru 2,6-bisphosphatase regulate the relative activities of the kinase/phosphatase. The N-terminus of the rat liver bifunctional enzyme is highly basic, containing a protein kinase A phosphorylation site that regulates these enzyme activities in a reciprocal manner. To determine the role of charged residues in the N-terminal peptide, mutant enzymes were constructed in which these residues were altered to residues carrying opposite charges, and the effect on the catalytic properties, thermal lability, and susceptibility to trypsin digestion and phosphorylation by protein kinase A was determined. Most of these mutations decreased k(cat)/K(ATP) and/or k(cat)/K(Fru) (6-P) of the kinase and increased k(cat)/K(Fru 2,6-P2) of the phosphatase. These mutant enzymes were more susceptible to trypsin digestion, phosphorylation by protein kinase A, and thermal inactivation. In general, the effect was greater with amino acid residues located more distant from the N-terminus. The resulting changes were not as large as observed with the phosphorylated enzyme. Mutation of Ser22 to Pro produced large changes in the kinetic properties comparable to those of phosphorylation, suggesting that the flexible region of the N-terminus containing five serines (Ser20 to S24) is essential for the enzyme activities. These results indicated that the charged residues as well as Ser20-Ser24 in the N-terminus of the liver Fru 6-P,2-kinase:Fru 2,6-Pase are essential in the allosteric regulation and probably involved in interactions with the catalytic domains that induce a conformation that has high Fru 6-P,2-kinase and low Fru 2,6-Pase activities. Any disruption of this N-terminal interaction results in inhibition of the kinase and activation of the phosphatase.