Glutathione-related enzyme activities in pregnant rat liver

The levels of GSH-related enzyme activities during pregnancy were determined. A significant increase in Selenium-dependent GSH peroxidase and GSH S-transferase E activity was observed. A concomitant increase in gamma-glutamylcysteine synthetase was measured, which indicated an increased ability to synthesize the tripeptide.     

Glutamine synthetase activity during mouse brain development

The specific activity of glutamine synthetase (GS) in mouse brain was 2-fold higher in the olfactory bulbs than in other regions. After birth, the specific activity of GS increased more rapidly in medulla oblongata and in olfactory bulbs, than in cerebral and cerebellar cortex. The activity of GS in primary cultures of brain hemispheres increased more slowly than in homogenates of whole brains. However, when astroblasts were treated in vitro with glucocorticoids or mouse brain extracts, GS activity reached 4 times the level measured in the homogenate of an adult mouse brain. We conclude that levels of GS activity may relate to the maturation of astrocytes, and propose that GS may be used as a marker of astrocytic maturation.     

Glutamine synthetase activity during mouse brain development

Summary The specific activity of glutamine synthetase (GS) in mouse brain was 2-fold higher in the olfactory bulbs than in other regions. After birth, the specific activity of GS increased more rapidly in medulla oblongata and in olfactory bulbs, than in cerebral and cerebellar cortex. The activity of GS in primary cultures of brain hemispheres increased more slowly than in homogenates of whole brains. However, when astroblasts were treated in vitro with glucocorticoids or mouse brain extracts, GS activity reached 4 times the level measured in the homogenate of an adult mouse brain. We conclude that levels of GS activity may relate to the maturation of astrocytes, and propose that GS may be used as a marker of astrocytic maturation.     

Control activities and regulation by the glucocorticoids of three urea-cycle enzymes in rat foetal liver: argininosuccinate synthetase, argininosuccinase and arginase (author's transl)]

The activity of three urea-cycle enzymes, argininosuccinate synthetase, argininosuccinase and arginase have been studied in the foetal and new-born liver of rats. The activity increases with regularity between 17.5 days of pregnancy and birth in control foetuses. The lack of corticosteroid from 18.5 days of pregnancy decreases the activity of argininosuccinate synthetase. After administration of cortisol (hydrocortisone), to these 18.5 day-old foetuses lacking of corticosteroids, both activities of argininosuccinate synthetase and arginase are enhanced.     

Occurrence of oxalyl-CoA synthetase in Indian pulses

Summary The presence of oxalyl-CoA synthetase was observed in common edible pulses. Excepting in chick pea, the changes in oxalyl-CoA synthetase activity of winter pulses proceeded in stages. The enzyme remained more active in late strains than in early strains of winter pulses. Unlike the activity of the enzyme in winter pulses, that in summer pulses behaved differently.     

Glutathione-related enzyme activities in pregnant rat liver

Summary The levels of GSH-related enzyme activities during pregnancy were determined. A significant increase in Selenium-dependent GSH peroxidase and GSH S-transferase E activity was observed. A concomitant increase in -glutamylcysteine synthetase was measured, which indicated an increased ability to synthesize the tripeptide.     

Inactivation of N-assimilating enzymes and proteolytic activities in wheat leaf extracts: Effect of pyridine nucleotides and of adenylates

Summary Nitrate reductase was protected from inactivation in wheat leaf extracts by NADH, while NADPH was less effective. NAD, NADP or adenylates did not affect nitrate reductase inactivation in vitro. Glutamine synthetase was more stable than nitrate reductase and was protected from inactivation by ATP. ADP, AMP or pyridine nucleotides had no or only a minor effect on the decrease of glutamine synthetase activity in extracts. The caseolytic activity extracted from senescing leaves was slightly decreased by NADH and NADPH but this effect was not sufficient to explain the stabilization of nitrate reductase by NADH. Oxidized pyridine nucleotides and adenylates had no major effect on the caseolytic activity under the conditions used.This work was supported by grant 3.067-0.81 from the Swiss National Science Foundation. Author for correspondence: U.F.     

Glutamine synthetase activity in subdivisions of brain of the shark, Squalus acanthias

Specific activity of glutamine synthetase in Squalus acanthias (spiny dogfish) central nervous system regions was highest in the cerebellum and lowest in the spinal cord. The levels of activity may relate to the excitability of each region by regulating the glutamate pool.     

Etamsylate as inhibitor of prostaglandin biosynthesis in pregnant human myometrium in vitro

Summary The effects of etamsylate on prostaglandin (PG) biosynthesis in microsomes of pregnant human myometrium in vitro have been determined, and compared with those of indomethacin. Both drugs inhibited PG biosynthesis, indomethacin being the more potent inhibitor of the two. Etamsylate inhibited synthesis of 6-oxo-PGF₁, PGF₂, PGE₂, and thromboxane B₂; increasing the concentration of etamsylate increased the inhibition of synthesis. It is suggested that etamsylate has no anti-cyclo-oxygenase activity, but acts by inhibiting the activity of prostacyclin synthetase, endoperoxide reductase, endoperoxide isomerase, and thromboxane synthetase.     

Stimulation of G-6-P independent glycogen synthase activity in the human placenta]

In immature human placentas, the activity of the I (glucose-6-phosphate-independent) form of glycogen synthase is significantly increased by insulin, glucose and by both compounds associated. In full-term placentas, the same kind of results has been found in each organ studied; due to the great variability observed in synthetase I control activities, the stimulation is significant only in the presence of insulin.     

Comparison of glutamate dehydrogenase and glutamine synthetase activities in the roots and aerial organs of an obligate halophyte: Suaeda maritima var. macrocarpa and a glycophyte: Phaseolus vulgaris, grown in presence of different concentration of NaCl]

The glutamate dehydrogenase and glutamine synthetase activities of an obligate halophyte, Suaeda maritima var. macrocarpa and a glycophyte. Phaseolus vulgaris are compared in function of salinity (increasing concentrations of NaCl) of the culturing solution. In culture, addition of NaCl stimulates glutamine synthetase activity and lowers glutamine dehydrogenase activity in the aerial organs and in the roots of Suaeda as opposed to what is observed in the glycophyte. Hence the obligatory halophily of Suaeda is related to an increase of the glutamine synthetase activity in a sal-trich medium corresponding to the stimulation of nitrate reductase and proteogenesis.     

Effect of carbenoxolone on phosphodiesterase and prostaglandin synthetase activities.

Carbenoxolone inhibited in vitro cAMP and cGMP phosphodiesterases in a concentration-dependent and noncompetitive manner. Prostaglandin synthetase activity of rabbit kidney medulla was slightly stimulated by carbenoxolone 0.1--0.5 mM, but inhibited by higher concentrations.     

Purification and properties of glutamine synthetase I fromRhizobium sp. UMKL 20

Summary Glutamine synthetase I was purified fromRhizobium sp. UMKL 20 following polyethylene glycol precipitation. The enzyme had a subunit molecular weight of 58 kd. Apparent K_m values for ammonia and glutamate were 5.6 and 15.2 mM, respectively. Glutamine synthetase I activity was inhibited by several end products of glutamine metabolism. The purified enzyme was highly adenylylated (E _n ^– =8.5).Acknowledgment. I would like to thank Mr J. C. Lai for technical assistance. This work was carried out with the support of Vote F 153/79 from the University of Malaya.     

The effects of various agents in vitro on homocarnosine-carnosine synthetase from rat brain

Summary The present paper reports the first evidence that homocarnosine-carnosine synthetase from rat brain requires free sulfhydryl groups for activity. The activity of the synthetase can be stabilized by dithioerythritol and inhibited strongly by Cu²⁺, Cd²⁺, Hg²⁺, Zn²⁺, and to a lesser extent by Ca²⁺, Ni²⁺, Li, chlorpromazine, -methyl DOPA and norepinephrine at the concentrations tested.Acknowledgment. This work was supported by United States Public Health Service Grant No. NS-06137.     

Evolution et contrôle de l'activité de l'argininosuccinate synthétase,de l'argininosuccinase et de l'arginase du foie foetal de rat

Summary The activity of three urea-cycle enzymes, argininosuccinate synthetase, argininosuccinase and arginase have been studied in the ftal and new-born liver of rats. The activity increases with regularity between 17.5 days of pregnancy and birth in control foetuses. The lack of corticosteroid from 18.5 days of pregnancy decreases the activity of argininosuccinate synthetase. After administration of cortisol (hydrocortisone), to these 18.5-day-old foetuses lacking of corticosteroids, both activities of argininosuccinate synthetase and arginase are enhanced.

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Ce travail a été réalisé avec l'aide de la Délégation Générale à la Recherche Scientifique et Technique (contrat N^o 737 1148).     

Effect of carbenoxolone on phosphodiesterase and prostaglandin synthetase activities

Summary Carbenoxolone inhibited in vitro cAMP and cGMP phosphodiesterases in a concentration-dependent and noncompetitive manner. Prostaglandin synthetase activity of rabbit kidney medulla was slightly stimulated by carbenoxolone 0.1–0.5 mM, but inhibited by higher concentrations.Acknowledgment. Supported by a grant from the Orion and Medica Scientific Foundation, Finland.     

Gene structure and function of the 2'-5'-oligoadenylate synthetase family

2'-5'-Oligoadenylate synthetase was among the first interferon-induced antiviral enzymes to be discovered. This family of enzymes plays an important role in the mechanisms of action of interferon antiviral activity, but is also involved in other cellular processes such as apoptosis and growth control. We have reviewed the function and genomic structure of this class of at least nine proteins. By studying the recently available data in the human genome database and the human Expressed Sequence Tag database, we have been able to build a comprehensive picture of the 2'-5'-oligoadenylate synthetase gene family and its precise location on chromosome 12. Chromosomal localization as well as the intron/exon structure of all four genes has been established and an overview of the splice variant forms of the 2'-5'-oligoadenylate synthetases arising from expression of the four genes is presented. Alignments of the human 2'-5'-oligoadenylate synthetase sequences with non-human 2'-5'-oligoadenylate synthetase sequences suggest that the exon structure and several amino acid sequence motifs have been conserved during evolution.     

Acetyl-coenzyme A synthetase (AMP forming)

Acetyl-coenzyme A synthetase (AMP forming; Acs) is an enzyme whose activity is central to the metabolism of prokaryotic and eukaryotic cells. The physiological role of this enzyme is to activate acetate to acetyl-coenzyme A (Ac-CoA). The importance of Acs has been recognized for decades, since it provides the cell the two-carbon metabolite used in many anabolic and energy generation processes. In the last decade researchers have learned how carefully the cell monitors the synthesis and activity of this enzyme. In eukaryotes and prokaryotes, complex regulatory systems control acs gene expression as a function carbon flux, with a second layer of regulation exerted posttranslationally by the NAD⁺/sirtuin-dependent protein acetylation/deacetylation system. Recent structural work provides snapshots of the dramatic conformational changes Acs undergoes during catalysis. Future work on the regulation of acs gene expression will expand our understanding of metabolic integration, while structure/function studies will reveal more details of the function of this splendid molecular machine.Received 4 December 2003; received after revision 2 March 2004; accepted 16 March 2004     

Effects of the chitin synthetase inhibitor plumbagin and its 2-demethyl derivative juglone on insect ecdysone 20-monooxygenase activity

The chitin synthetase inhibitor plumbagin and its 2-demethyl derivative juglone were found to inhibit in a dose-response fashion the cytochrome P-450 dependent ecdysone 20-monooxygenase activity associated with adult female Aedes aegypti, wandering stage larvae of Drosophila melanogaster, and fat body and midgut from last instar larvae of Manduca sexta. The concentration of these naphthoquinones required to elicit a 50% inhibition of the steroid hydroxylase activity in all the insects was approximately 1 x 10(-4) M.     

Glutamine synthetase activity in subdivisions of brain of the shark,Squalus acanthias

Summary Specific activity of glutamine synthetase inSqualus acanthias (spiny dogfish) central nervous system regions was highest in the cerebellum and lowest in the spinal cord. The levels of activity may relate to the excitability of each region by regulating the glutamate pool.Publication No. 14 from the Laboratory of Biochemical Ecology. Contribution No. 527, College of Fisheries, University of Washington. This work was supported in part by a fellowship from the national Wildlife Federation and a Pacific Fisheries Biologists' scholarship to J.T.W.