Metabolism of secondary alcohols in Drosophila melanogaster: Effects on alcohol dehydrogenase

• 1.1. In vivo metabolism of a secondary alcohol in Drosophila melanogaster and its effects on alcohol dehydrogenase (ADH) have been studied.
• 2.2. ADH-mediated breakdown of the secondary alcohol, propan-2-ol, was the main source of the acetone produced.
• 3.3. Acetone formation declined and stopped ultimately, suggesting inhibition of ADH activity in vivo which has been confirmed in in vitro studies.
• 4.4. A powerful ketone-trapping agent, semicarbazide, did not restore the ADH activity in vitro, whereas aldehyde substrates of ADH did restore activity.
• 5.5. The final formation of a dead-end ADH:NAD-acetone ternary complex has been proposed and its consequences discussed.

     

Lactate dehydrogenase isozymes of the leopard danio,Brachydanio nigrofasciatus: their characterization and ontogeny

• 1.1. The tissue specific patterns and ontogeny of lactate dehydrogenase (LDH) are reported.
• 2.2. While all tissues (eye, brain, heart, intestine, liver, ovary and skeletal muscle) show isozymes of A and B subunit composition, only liver extracts possess isozymes resulting from C subunit synthesis.
• 3.3. The A₄ homopolymer appears simultaneously with initial muscle contractility and is correlated with the physiological function of muscular contraction.
• 4.4. The activation of the Ldh-C locus is correlated with the first functioning of liver. It is suggested that the state of differentiation of liver cells may be the stimulus required for C locus expression.

     

Kinetic interpretations of active site topologies and residue exchanges in Drosophila alcohol dehydrogenases

• 1.1. A comparison of full and partly sequenced Adhs from various Drosophila species reveal that 127 of their 253–255 positions are identical (50% identity).
• 2.2. Fifty-six of the 115 C-terminal amino acids building up the alcohol binding region differ. In spite of the large differences in primary structure of the alcohol binding region in the Adh enzyme in distantly related Drosophila species, the substrate specificity and stereospecificity have been retained. The topology of the alcohol binding region has been largely conserved during evolution.
• 3.3. The primary structures of the alcohol dehydrogenases (Adh) in the Sophophora subgenus is distinguished by few amino acid exchanges, and kinetic and activity parameters show that those at positions 14, 82, 192 and 214 are directly or indirectly involved in coenzyme binding.
• 4.4. In these non-metallo Adhs, a tyrosine has been tentatively identified as a nucleophilic catalyst of the hydride transfer step. The three tyrosines at positions 63, 152 and 178 are conserved among the Drosophila alcohol dehydrogenases.

     

The secretion of anti-diuretic hormone during a rise of body temperature in the pig (Sus scrofa)

• 1.1. In pigs (Sus scrofa) exposed to hyperthermic conditions, when the rectal temperature rose from 38.9–42.3°C. plasma antidiuretic hormone (ADH) increased from 0.8 μU/ml to 11.4 μU/ml; arterial pressure, blood oxygen saturation and haematocrit increased and Pco, fell.
• 2.2. On three occasions out of six attempts, a large infusion of saline or dextran into the superior vena Cava during the rise of body temperature suppressed the expected rise of plasma ADH.
• 3.3. Forced ventilation of anaesthetized normothermic pigs elicited a similar rise in circulating ADH.

     

IDentification of a microsomal retinoic acid synthase as a microsomal cytochrome P-450-linked monooxygenase system

• 1.1. To characterize an enzyme which metabolizes retinal in liver microsomes, several properties of the enzymatic reaction from retinal to retinoic acid were investigated using rabbit liver microsomes.
• 2.2. The maximum pH of the reaction in the liver microsomes was 7.6.
• 3.3. The K_m and V_max values for all-trans, 9-cis and 13-cis-retinals were determined.
• 4.4. The reaction proceeded in the presence of NADPH and molecular oxygen.
• 5.5. The incorporation of one atom of molecular oxygen into retinal was confirmed by using oxygen-18, showing that the reaction comprised monooxygenation, not dehydrogenation.
• 6.6. The monooxygenase activity was inhibited by carbon monoxide, phenylisocyanide and antiNADPH-cytochrome P-450 reductase IgG, but not by anti-cytochrome b₅ IgG.
• 7.7. The enzymatic activity inhibited by carbon monoxide was photoreversibly restored by light of a wavelength of around 450 nm.
• 8.8. The retinal-induced spectra of liver microsomes with three isomeric retinals were type I spectra.
• 9.9. The microsomal monooxygenase activity induced by phenobarbital or ethanol were more effective than that by 3-methylcholanthrene, clotrimazole or β-naphthoflavone.
• 10.10. These results showed that the monooxygenase reaction from retinal to retinoic acid in liver microsomes is catalyzed by a cytochrome P-450-linked monooxygenase system.

     

Further studies on the phylogenetic distribution of pyruvate oxidoreductase activities

• 1.1. The phylogenetic distribution of lactate, octopine, alanopine and strombine dehydrogenase activities (respectively, LDH, ODH, ADH and SDH) was examined in over 60 species from seven phyla and from three continents.
• 2.2. The results confirm and extend previously published data. Consistencies of distribution are observed at the levels of phyla, class, order and family.
• 3.3. Major observations include prominent SDH in the Porifera; LDH only in the Polyplacophera, Nudibranchia and Myidae (Mollusca) and nereid worms (Polychaeta); ODH and SDH in the marine pulmonate Melampus bidentatus (Basommatophora); high ADH to SDH ratios in marine gastropods; high ODH in active molluscs; and apparent SDH in the barnacle Lepas anatifera.
• 4.4. The results are discussed in relation to theories of opine pathway evolution and the newly discovered tauropine and β-alanopine opine dehydrogenases.

     

NAD(P)H dehydrogenase from rabbit and rat liver: Purification and some properties

• 1.1. NAD(P)H dehydrogenase from rabbit liver was purified to electrophoretic homogeneity using a procedure also found applicable for the rat liver enzyme.
• 2.2. Rabbit and rat liver enzymes showed different behaviour in isoelectric focusing and different K_m values and turnover numbers.
• 3.3. Both enzymes were inhibited to similar extents by warfarin.
• 4.4. The rabbit enzyme is composed of two subunits of mol. wt 27,000 and contained 1 FAD group per subunit.
• 5.5. Some absorption and circular dichroism properties of the rat enzyme are shown.

     

Purification and characterization of monkey albumin and proalbumin

• 1.1. Albumin purified from rhesus monkey (MSA) shows immunological cross-reactivity with human serum albumin (HSA) by RIA.
• 2.2. The amino-terminal sequence of MSA shows a high degree of homology to HSA.
• 3.3. Thirty minutes after injection of radioactive leucine directly into the portal vein, albumin was purified chemically from the liver, kidneys and serum.
• 4.4. At this time, 15% of the label was incorporated into liver homogenate protein.
• 5.5. A highly labelled immunoreactive albumin form was purified from liver to constant specific radioactivity and separated from tissue and serum albumin.
• 6.6. The specific radioactivity of this proalbumin was 36-times higher than the specific radioactivity of albumin in liver tissue.
• 7.7. These similarities to HSA suggest that this non human primate species can serve as a useful model of human albumin synthesis in vivo.

     

Changes in the phospholipid composition and in fatty acids of phosphatidylcholine and phosphatidylethanolamine of various tissues of the developing tadpole of Agalychnis dacnicolor

• 1.1. Lipid changes occur in the developing tadpole of A. dacnicolor. The phosphatidylcholine content of liver and tail decrease during metamorphosis.
• 2.2. In liver, the fatty acids of phosphatidylcholine and phosphatidylethanolamine become more unsaturated.
• 3.3. In skin, phosphatidylcholine becomes more unsaturated and phosphatidylethanolamine becomes more saturated.
• 4.4. In tail, phosphatidylcholine becomes more saturated and phosphatidylethanolamine shows no change.
• 5.5. Triglycerides become more unsaturated in skin but become more saturated in tail.

     

Human GMP synthetase

• 1.1. The specific activity of GMP synthetase was measured in several human tissues and found to be highest in cultured skin fibroblasts, followed by bone marrow, leukocytes, erythrocytes. placenta, and liver.
• 2.2. The enzyme from fibroblasts was purified approximately 50-fold by ammonium sulfate fractionation and gel filtration.
• 3.3. The K_m values were determined to be 4.9μM for XMP, 270μM for ATP. and 340 μM for glutamine.
• 4.4. Ammonium sulfate could replace glutamine as the amino donor but was much less efficient.
• 5.5. The enzyme was specific for ATP as the energy source.
• 6.6. Unlike the calf thymus enzyme, the human enzyme has no requirement for a reduced sulfhydryl compound.
• 7.7. Human GMP synthetase is inhibited by ATP, dATP, azaserine, and hydroxylamine.

     

The effect of hypoxia on carbohydrate metabolism in flounder (Platichthys flesus L.)—I. Utilization of glycogen and accumulation of glycolytic end products in various tissues

• 1.1. Resting oxygen consumption at 10°C did not change from normoxia (150 mm Hg) down to an oxygen tension of 55 mm Hg for the flounder, Platichtys flesus.
• 2.2. Flounders exposed to hypoxia showed increased levels of blood glucose and lactate, dependent on the degree of hypoxia.
• 3.3. Due to hypoxia glycogen was depleted in the liver and swimming muscle but in the heart there was no significant change.
• 4.4. Liver glucose increased after 7 hr of hypoxia. Heart and muscle glucose did not change but the absolute glucose concentration in the heart was five times higher than in the muscle.
• 5.5. There is a transient accumulation of lactate in heart, liver and kidney after 7 hr of hypoxia while lactate accumulation in the swimming muscle is significant only after 21 hr of hypoxia.
• 6.6. Succinate only accumulated in the liver while alanine accumulated in muscle, heart and liver.

     

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.

     

Temperature acclimation in respiratory and cytochrome c oxidase activity in common carp (Cyprinus carpio)

• 1.1. Common carp (Cyprinus carpio) exposed to experimental temperatures of 12, 18, 24, 30 or 36°C for a 4-week period were used to investigate the effect of temperature acclimation on the frequency of opercular movement (FOM), growth and cytochrome c oxidase (CCO) activity in heart, liver and muscle.
• 2.2. An exponential relationship between FOM and temperature after the first week (10₁₀ =1.76) disappeared after the second week.
• 3.3. The initially high FOM at temperatures of 30 or 36°C and the low FOM at 18 or 12°C changed over 4 weeks to approach the FOM of fish at 24°C.
• 4.4. This change in the relationship of FOM to temperature from highly dependent to independent appeared to be thermal compensation.
• 5.5. Heart and liver CCO activities were significantly affected by temperature, with the lowest activity at the approximate optimum temperature for growth, 24°C.
• 6.6. Highest CCO activities for heart and liver occurred at both the highest and lowest temperatures.
• 7.7. Among the three tissues, heart CCO activity was generally the highest and most affected by acclimation temperature.
• 8.8. Muscle tissue had the lowest CCO activity and was unaffected by temperature.
• 9.9. The high CCO activity at a cold acclimation of temperature 12°C was probably due to thermal compensation and the high activity at 36°C may have been a result of thermal stress.

     

Reducing equivalent transport by substrate shuttles in rat liver and colon

• 1.1. The observed level and subcellular distribution of the α-glycerophosphate and malate-aspartate substrate shuttle enzymes in liver and colon were consistent with their proposed roles in reducing equivalent transport.
• 2.2. K_m value determinations of shuttle enzymes were performed.
• 3.3. Substrate shuttles were reconstructed from isolated liver and colon mitochondria which displayed satisfactory respiratory control and P:O ratios.
• 4.4. The results obtained suggest that while the malate-aspartate shuttle is the primary means of reducing equivalent transport in the liver, the α-glycerophosphate shuttle predominates in the colon.

     

Liver glycogen mobilization by Trypanosoma brucei sonicates

• 1.1. The African trypanosome, T. brucei, appears to possess a hormone-like substance capable of stimulating the production of glucose from glycogen.
• 2.2. The effect of this substance is primarily on the liver as demonstrated in vitro.
• 3.3. The effect is consistent and independent of host conditions provoking an immune response.
• 4.4. The data are discussed with respect to the endocrinological aspects of the host and its corresponding involvement.

     

Seasonal changes of total lipids in the turtle Sternotherus odoratus

• 1.1. Seasonal variation in total lipids was examined in several body components of the turtle Sternotherus odoratus.
• 2.2. Carcass fat stores in both sexes were depleted during winter. Additionally, a decline in carcass lipids was associated with increases in gonadal mass.
• 3.3. Concentrations of liver lipids were maximal during August and minimal during winter.
• 4.4. Males showed little seasonal change in plasma lipid levels, whereas females had seasonal peaks temporally associated with ovarian development and carcass fat storage.
• 5.5. Ovarian concentrations of lipids were minimal after nesting and increased during fall.
• 6.6. Results suggest that S. odoratus uses stored fats both for reproduction and maintenance during winter.

     

Kinetic properties of cat liver microsomal glucose-6-phosphatase

• 1.1. Cat liver microsomes contain the multifunctional enzyme glucose-6-phosphatase.
• 2.2. High specificity was shown for the phosphohydrolase as well as for the transferase activity.
• 3.3. Both activities have high V_max values determined in optimized conditions.
• 4.4. The phosphate transfer with carbamyl-phosphate as a phosphoryl donor and d-glucose as acceptor is consistent with a random mechanism in which the binding of one substrate decreases the enzyme's affinity for the second substrate.

     

Ostrich fructose-1,6-bisphosphatase: Kinetic characterization of the liver isoenzyme

• 1.1. Purified ostrich (Struthio camelus) liver fructose-1,6-bisphosphatase exhibited an absolute requirement for Mg²⁺.
• 2.2. The enzyme catalyzed the hydrolysis of fructose-1,6-bisphosphate, sedoheptulose-l,7-bisphosphate and ribulose-l,5-bisphosphate.
• 3.3. S_0.5 for substrate was 1.4 μM.
• 4.4. AMP was a potent non-competitive inhibitor with respect to substrate (K_i of 25 μM).
• 5.5. Fructose-2,6-bisphosphate was a potent competitive inhibitor of the enzyme (K_i of 4.8 μM).

     

Studies on tryptophan pyrrolase of Schistocerca gregaria försk. (Orthoptera)

• 1.The trytophan pyrrolase activity of central fat bodies of S. gregoria hoppera was studied.
• 2.The enzyme system appears to be similar to that of mammalian liver.
• 3.The enzyme was localized only in central fat bodies.
• 4.Extracts of other body parts can mimic an enzyme activity because of a degradation of ommochromes in the enzyme test.

     

DNase-I-like enzyme from the carp liver—Inhibition by muscle and endogenous actin

• 1.1. DNase-I-like activity occurs in the carp (Cyprinus carpio) liver cytosol (supernatant 105,000g).
• 2.2. The enzyme resembles DNase I from bovine pancreas in respect to the molecular mass (~31 kDa), pH (7.4) and ion requirements (Mg²⁺, Ca²⁺) and the ability to degrade native as well as denatured DNA.
• 3.3. As judged by comparison of DNase zymograms obtained after native- and SDS-PAGE, the enzyme occurs in the three molecular forms of similar molecular weight and different charges.
• 4.4. All these forms are inhibited by rabbit skeletal muscle actin as well as by endogenous actin isolated from the carp liver cytosol.
• 5.5. DNase from the carp liver cytosol does not interact with the antibodies directed against DNase I from bovine pancreas and against DNase I from the rat and bovine parotid glands.