The effect of changes in external salinity on the free amino acids and two aminotransferases of white muscle from fasted Salmo gairdneri Richardson

• 1.1. Aspartic acid. glutamic acid and serine concentrations in the white muscle of starved rainbow trout kept in diluted sea water (600 mOsm/l) for 8 days were significantly higher than in control animals kept in fresh water.
• 2.2. After 24 days the levels of all amino acids investigated (aspartic acid, glutamic acid, serine, glycine. alanine, threonine and lysine) in the white muscle of starved rainbow trout kept in diluted sea water were higher than in the white muscle of animals kept in fresh water without food.
• 3.3. Alanine aminotransferase activity in starved rainbow trout kept in diluted sea water for 24 days was higher than in the control animals kept in fresh water.
• 4.4. There is a significant correlation between alanine concentration and alanine aminotransferase activity in the white muscle of rainbow trout.

     

Ca2+-dependent stimulation of muscle and liver phosphorylase kinase by heparin

• 1.1. Heparin stimulates the activity of nonactivated and activated skeletal muscle phosphorylase kinase in a Ca²⁺-dependent manner.
• 2.2. The stimulatory effect of heparin on the activity of nonactivated phosphorylase kinase is also expressed in the presence of calmodulin and glycogen. Heparin acted in synergism with glycogen.
• 3.3. Heparin increases the affinity of phosphorylase kinase to Ca²⁺ 5–12 fold depending upon the activation conditions.
• 4.4. Ca²⁺ influences the stimulation of liver phosphorylase kinase by heparin in a similar way.

     

Arginase,ornithine decarboxylase and S-adenosylmethionine decarboxylase in chicken brain and retina

• 1.1. Arginase, ornithine decarboxylase and S-adenosylmethionine decarboxylase are active in both retina and brain. Activity is higher in cerebellum than in the cerebral hemispheres and optical lobes.
• 2.2. Arginase and ornithine decarboxylase are very active in the retina of very young chicks, while S-adenosylmethionine decarboxylase is poorly active. By contrast, S-adenosylmethionine decarboxylase is much more active in brain.
• 3.3. The pattern of activity during development is different; only ornithine decarboxylase is very active during embryonal life; S-adenosylmethionine decarboxylase, at all events in brain, is more active in adult life.
• 4.4. Ornithine decarboxylase is inhibited in vitro by α-difluoromethylornithine, but not in vivo. Diaminopropane inhibits brain ornithine decarboxylase, but does not induce an ornithine decarboxylase-antizyme.
• 5.5. Methylglyoxal bis(guanylhydrazone) promotes an increase of S-adenosylmethionine decarboxylase activity in both the brain and the retina in vivo.

     

Activity of some enzymes involved in the metabolism of polyamines in the liver of streptozotocin-diabetic rats

• 1.1. The effect of diabetes on some enzymes of polyamine metabolism was studied in male rats 1–12 days after administration of streptozotocin.
• 2.2. Hepatic ornithine decarboxylase activity decreased in the first days after the administration, but increased thereafter. The decrease was not due to an alteration of the ODC-antizyme concentration, nor to a posttranslational modification catalyzed by transglutaminase.
• 3.3. S-adenosylmethionine decarboxylase and ornithine transaminase were both increased.
• 4.4. Spermicline acetyltransferase activity was practically unchanged, while its inactivating factor was markedly decreased.

     

Kinetic studies of the transphosphorylation reactions catalyzed by alkaline phosphatase from E. coli: Hydrolysis of p-nitrophenyl phosphate and o-carboxyphenyl phosphate in presence of tris

• 1.1. Transphosphorylation of p-nitrophenyl phosphate and o-carboxyphenyl phosphate to Tris, has been studied at alkaline and acid pH.
• 2.2. The rate of release for all reactions products was Tris-dependent for both substrates, with a slight maximum for phenol at alkaline pH. These dependences have been analyzed from a mechanistic standpoint.
• 3.3. Individual constants of rate of a simple transphosphorylation mechanism have been determined.
• 4.4. At high Tris concentrations (> 1.0 M) a slight competitive inhibition has been observed.
• 5.5. Inhibition in NH₄⁺-NH₃Cl buffer has been found at alkaline pH but not at acid pH. It would therefore seem that the non-protonated NH₂ group of Tris is responsible for inhibition.
• 6.6. The results suggest the formation of complexes between Tris and the enzyme. Other possible alternatives are also analyzed.

     

Time related changes in the free amino acid pool of the sea anemone,Bunodosoma cavernata,during salinity stress

• 1.1. The sea anemone, Bunodosoma cavernata, is a relatively eurybaline cnidarian tolerating salinities from 12 to 40%.
• 2.2. Taurine, glutamic acid and aspartic acid all showed some increases with increased salinity.
• 3.3. The amino acid showing the greatest accumulation under high salinity conditions was β-alanine which increased 28-fold from 1.5 to 41.9 μmol/g dry weight when salinity was raised from 26 to 40%.
• 4.4. When B. cavernata was subjected to increased salinity, β-alanine was rapidly accumulated and reached maximum levels within 4 days.
• 5.5. When salinity was dropped from 36 to 26%0, β-alanine concentrations dropped from 15 to 2 μmol/g dry weight in 2 days.

     

Effect of berenil on polyamine metabolism in primary cultured rat hepatocytes

• 1.1. Putrescine and spermidine content increased in hepatocytes during culture. In the presence of 10 μM Berenil, putrescine content was further increased, while the increase of spermidine was prevented.
• 2.2. Ornithine decarboxylase activity was markedly reduced, and to a lesser extent also S-adenosyl-methionine decarboxylase activity.
• 3.3. Berenil appears to promote an increase in the transformation of spermidine into putrescine, and to inhibit the polyamine efflux.

     

The synthesis of acetyl phosphate by homogenates of elasmobranch liver

• 1.1. Cetyltrimethylammonium bromide extracts of elasmobranch liver are shown to have acetyl kinase activity. The conditions resulting in activity are different from those resulting in carbamoyl phosphate synthetase activity in the same tissue. The possibility that the two activities are due to the same enzyme, however, is not ruled out.
• 2.2. Progress curves suggesting that a time-dependent activation process may be involved in the case of aged and frozen extracts were obtained.
• 3.3. Omission of N-acetyl glutamate from the assay mixture reduces acetyl kinase activity by about 30 per cent.

     

The erythrocytes of the metallic skink Niveoscineus metallicus

• 1.1. We studied the haemoglobin content, erythrocyte indices, erythrocyte enzymes and haemoglobin electrophoresis patterns of the metallic skink Niveoscineus metallicus and compared them to the small amount of published data on other small lizards.
• 2.2. Haemoglobin was much lower than that recorded for the salamander.
• 3.3. Erythrocyte enzymes (glucose phosphate isomerase and glucose 6 phosphate dehydrogenase) were lower in the skink than in the salamander. Glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase and pyruvate kinase were much higher in the skink than in the salamander.
• 4.4. A single, slow, haemoglobin component was identified by electrophoresis.

     

Cooperative atp inhibition and fructose-1,6-biphosphate activation of rat liver pyruvate kinase

• 1.1. For the determination of relationship between FDP and ATP in the rat liver pyruvate kinase regulation, kinelic studies have been carried out at several ATP and FDP concentrations.
• 2.2. The results obtained on FDP activation show a great cooperativity for FDP saturation with a Hill coefficient of h = 2.79.
• 3.3. Kinetic studies on ATP inhibition also show a great cooperativity for ATP saturation (h = 2.84) at high FDP concentrations.
• 4.4. These results may contribute to explain the regulation of rat liver pyruvate kinase accounting for the activity of this enzyme at high FDP concentrations modulated by small changes in ATP concentrations.

     

Phosphorylation of a 25,000-dalton protein in slow and fast muscles of the chicken

• 1.1. Protein phosphorylation in intact chicken latissimus dorsi muscle, slow anterior (ALD) and fast posterior (PLD), was compared.
• 2.2. A major difference in [³²P]phosphate incorporation was found between the ALD and PLD in a 25,000-dalton heat soluble protein.
• 3.3. The 25,000-dalton protein was purified from both the ALD and PLD.
• 4.4. The two proteins had similar amino acid composition and both contained approximately 1 mole phosphate per mole of protein.
• 5.5. The difference in their content of radioactive phosphate was determined to be due to faster turnover in the ALD.

     

Chemical feeding stimulants for the herbivorous fish,Tilapia zillii

• 1.1. Chemical feeding stimulants for an herbivorous fish, Tilapia zillii have been determined by fractionation and bioassay of substances derived from a model food plant.
• 2.2. Stimulation was produced by amino acids; glutamic acid, aspartic acid, serine, lysine and alanine produced the bulk of stimulatory activity.
• 3.3. These amino acids are among the most abundant in the test plant, and are markedly different from the amino acids found to stimulate feeding in carnivorous fish.
• 4.4. On the basis of these results, a chemically-mediated mechanism of feeding niche separation is postulated.

     

Acid and alkaline phosphomonoesterase activities in snake venoms

• 1.1. Acid and alkaline phosphatase activities of eight different snake venoms were determined quantitatively by using synthetic substrates, o-carboxyphenylphosphate and p-nitrophenylphosphate respectively.
• 2.2. It was found that most of Elapidae venoms investigated had both acid and alkaline phosphatase activities.
• 3.3. Three Crotalidae venoms investigated did not show any alkaline phosphatase activity.
• 4.4. The strength of venom acid phosphatase activity is as follows: Agkistroden acutus > Naja haje > Naja naja samarensis > Naja naja atra > Naja melanoleuca.
• 5.5. The strength of venom alkaline phosphatase activity by using p-nitrophenylphosphate is in the order of Naja hannah > Naja haje > Naja naja samarensis > Naja naja atra > Naja melanoleuca.When o-carboxyphenylphosphate was used as a substrate, the order of enzyme activity is Naja hannah > Naja haje > Naja naja samarensis > Naja melanoleuca > Naja naja atra.
• 6.6. Acid phosphatase activity of all the Elapidae venoms was inhibited completely by fluoride. The alkaline phosphatase activity of Elapidae venoms was not inhibited by fluoride either using p-nitrophenylphosphate or o-carboxyphenylphosphate.
• 7.7. The acid phosphatase of all the Elapidae venoms was not inhibited by zinc ion. However, most of the venom alkaline phosphatases were inhibited by zinc ion.
• 8.8. Ethylenediaminetetraacetic acid (EDTA) had inhibitory action on venom phosphatase activity. However, tris-(hydroxymethyl)-aminoethane had a counter effect on the inhibitory action of EDTA.
• 9.9. Optimum pH studies of the snake venom phosphatases showed that the acid phosphatases of the snake venoms had their highest activity in the range of pH 4–5. The alkaline phosphatases of the snake venoms had their optimum pH at 9.
• 10.10. Comparable experiments were also conducted by using chicken intestine alkaline phosphatase and wheat germ acid phosphatase.

     

Essential tyrosyl residues of human placental alkaline phosphatase

• 1.1. Human placental alkaline phosphatase was inactivated with tetranitromethane in a biphasic process.
• 2.2. Spectral and amino acid analysis demonstrated that the inactivation was due to the conversion of tyrosine residues to 3-nitrotyrosine.
• 3.3. The inactivation process showed saturation kinetics.
• 4.4. Protection of the enzyme against tetranitromethane inactivation was afforded by inorganic phosphate.
• 5.5. The binding affinity between the modified enzyme and inorganic phosphate was decreased.
• 6.6. Our results suggest the involvement of tyrosyl residues in the locus of phosphoryl site of the phosphorylated enzyme forms.

     

Inactivation of yeast alcohol dehydrogenase by 2-mercaptoethanol: Loss of zinc from the active centre

• 1.1. Yeast alcohol dehydrogenase was inactivated by 2-mercaptoethanol (50 mM or greater).
• 2.2. The commercial enzyme preparation used had 10.4g-atom zinc/molecule. Dialysis against ethylene-diaminetetraacetic acid solution lowered this value to 4.4 g-atom/molecule.
• 3.3. Exposure to 500 mM 2-mercaptoethanol and subsequent dialysis lowered the zinc content to 1.4 g-atom/molecule, and caused a loss of enzyme activity (95%).

     

S-Adenosyl-l-methionine decarboxylase activities in Mytilus edulis

• 1.1. The activities of S-adenosylmethionine decarboxylase (EC 4.1.1.50) were measured in cell extracts of mantle, hepatopancreas and foot from Mytilus edulis.
• 2.2. The apparent molecular weights of the enzymes estimated by gel filtration chromatography were 65,000 ± 10,000.
• 3.3. The enzymes do not require bivalent cations for catalysis and show optimum pH between 7.0–8.0 in phosphate buffer.
• 4.4. The hepatopancreas enzyme shows different behavior to the other two enzymes against temperature and its activity is strongly inhibited by NH₄⁺.
• 5.5. The apparent K_ms for S-adenosylmethionine were found to be 300, 200 and 250 μM for the hepatopancreas, mantle and foot enzymes, respectively.

     

Regulatory properties of rabbit liver phosphorylase kinase

• 1.1. Purified native rabbit liver phosphorylase kinase becomes activated during the assay of its activity while low molecular weight forms of the same enzyme do not.
• 2.2. The activation requires ATP and maganesium ions, suggesting the phosphorylation of the enzyme by a protein kinase as the mechanism involved.
• 3.3. The activation of the enzyme can be reverted by the action of a type 1 protein phosphatase isolated from the same tissue.
• 4.4. The activation can also be catalyzed by the catalytic subunit of cAMP-dependent protein kinase in a process that requires a much lower ATP concentration to proceed.
• 5.5. The activation is believed to be due to an autocatalytic phosphorylation of phosphorylase kinase itself. In support of this hypothesis are the regulation of the process through calcium ions, the low levels of endogenous protein kinase detected in the purified preparation, the high ATP concentrations required in the absence of cAMP dependent protein kinase and the fact that the process cannot be blocked by an excess of the heat stable inhibitor specific for the later enzyme.
• 6.6. The low molecular weight forms of the enzyme on their side are not affected by the action of neither protein phosphatase 1 nor cyclic AMP dependent protein kinase.
• 7.7. Both activated and nonactivated phosphorylase kinase are partially dependent on calcium ions, the affinity of the former being higher than that of the latter. The low molecular forms do not require calcium ions to express their activity.

     

Acute hepatic porphyria syndrome with porphobilinogen synthase defect

On the basis of metabolite and enzyme studies a new type of acute hepatic porphyria with porphobilinogen synthase defect and repeated intermittent acute manifestations, abdominal colics, tachycardia and hypertension, and a persistent neurological syndrome was found in two young male patients. The main characteristic features are the following:

• 1.1. High urinary δ-aminolevulinic acid excretion( ⪢ 1 mmol/24hr), slight increase of porphobilinogen (up to 25 μmol/24 hr) and high increase of porphyrins (up to 22 μmol/24 hr) with coproporphyrin dominance.
• 2.2. Normal fecal and liver porphyrins.
• 3.3. Slight increase of erythrocyte protoporphyrin.
• 4.4. Decrease of porphobilinogen synthase activity in erythrocytes in both cases below 1% of healthy and not lead-exposed persons; normal activities of uroporphyrinogen synthase and decarboxylase in erythrocytes.
• 5.5. Low-normal lead concentrations in blood and low-normal lead excretion in urine in both cases; normal lead content in bone.
• 6.6. Normal plasma and urinary amino acids.
• 7.7. Irrelevant hepatological (liver biopsy), general clinical chemical and hematological findings.
• 8.8. Diminished activity of porphobilinogen synthase in nearly all family members of both patients. From these investigations it can be concluded that there is no exogeneous, “toxic” cause of this porphyria. Porphobilinogen synthase in lead poisoning is not diminished to such an extent as demonstrated here; in contrast to lead intoxication, porphobilinogen synthase activity cannot be activated or reactivated by thiols. All clinical and pathobiochemical data point at a new enzymatic type of endogeneous acute hepatic porphyria with intermittent acute manifestations, clinically analogous to so-called acute intermittent porphyria. Porphyrin precursors and porphyrin excretion both reflects the enzymatic defect and the regulatory consequences starting with the induction of δ-aminolevulinic acid synthase.

     

Effects of aluminium and pH on calcium fluxes,and effects of cadmium and manganese on calcium and sodium fluxes in brown trout (Salmo trutta L.)

• 1.1. Simultaneous measurement of calcium fluxes in brown trout, at low external [Ca] (20 μ mol 1⁻¹), provided evidence of active uptake of Ca from the medium.
• 2.2. At pH 4.5, calcium influx was inhibited and efflux was stimulated.
• 3.3. Cd and Mn, but not Al, at concentrations within the ranges found in acid waters experiencing fish population decline, inhibited calcium influx. Efflux was unaffected.
• 4.4. Cd and Mn stimulated sodium influx and efflux.

     

Purification and some properties of an atypical alkaline p-nitrophenylphosphate phosphatase activity from Halobacterium halobium

• 1.1. An alkaline p-nitrophenylphosphate phosphatase has been purified 440-fold from extracts of Hatobacterium halobium.
• 2.2. The enzyme has an apparent molecular weight of 24,000.
• 3.3. A K_m value for p-nitrophenylphosphate of 1.12mM has been found under optimal conditions.
• 4.4. The enzyme is selectively activated and stabilized by Mn²⁺.
• 5.5. It requires high salt concentrations for stability and maximum activity.
• 6.6. It displays an unusual restricted substrate specificity of 25 phosphate esters tested, only phosphotyrosine and casein were hydrolysed besides p-nitrophenylphosphate.