Diversity of the effect of phosphatidylcholine and sphingomyelin on adenylate deaminase from pig brain

Liposomes made of sphingomyelin were found to inhibit both ATP-activated and non-activated AMP deaminase from pig brain, in contrast to liposomes made of egg yolk phosphatidylcholine which exhibited an activating effect on the ATP-activated enzyme, being without effect on AMP deaminase in the absence of ATP. Dioleoylphosphatidylcholine exerted a similar effect as egg yolk phosphatidylcholine but dipalmitoylphosphatidylcholine was without effect.     

Allosteric modification of adenylate deaminase activity: appearance of adenosine deaminase activity as an effect of potassium ions]

The activation of purified adenylate deaminase from the duck myocardium by K+ is accompanied by modification of the substrate specificity and by the appearance of the capacity to deaminate adenosine and adenine. Adenosine deaminase activity originates at the concentration of K+ of 0.15 M that possesses the most stimulating effect on adenylate deaminase activity; with the increase of potassium ions concentration adenosine deaminating activity is enhanced as well, with a parallel reduction of Hill's constant. The PH-dependence, mode of inhibition by phosphate ions and the effect of alkaline metals suggests that adenosine deamination is carried out by natural adenylate deaminase active centres when their conformation is changed under the activator action.     

Modification of pig heart lipoamide dehydrogenase by cupric ions.

The insertion of a second disulfide bridge into native pig heart lipoamide dehydrogenase, requires two Cu-2+ ions for each catalytic center inactivated under anaerobic conditions. During inactivation, both metal atoms become reducible by their juxtaposition to the two participating cysteine residues and may be removed as the Cu+-chelates of neocuproine and bathocuproinesulfonate, leaving an additional disulfide bridge on the protein. Inactivation does not require the presence of oxygen, but when substoichiometric levels of copper are used under aerobic conditions the slow regeneration of Cu-2+ becomes rate-limiting. The course of aerobic inactivation is markedly biphasic at 0 degrees using 2 Cu-2+/FAD, with 30% of the total change completed rapidly, followed by a much slower phase. Both the extent of the fast phase and the rate of the second phase are enhanced by increasing levels of Cu-2+, but are relatively unaffected when the Cu-2+/FAD ratio is maintained at 2 and the protein concentration is varied. The enzyme affords several binding sites for Cu-2+ at pH 7.8, and it is suggested that competition between these sites during the initial statistical distribution of metal ions may explain this biphasic behavior.     

Activity of adenosine deaminase and adenylate deaminase on adenosine and 2', 3(')-isopropylidene adenosine: role of the protecting group at different pH values

The deamination rate of 2',3'-isopropylidene adenosine catalyzed by adenosine deaminase (ADA) from calf intestine and adenylate deaminase (AMPDA) from Aspergillus species has been evaluated and compared with that of the enzymatic reactions of adenosine, to elucidate the influence of the protecting group on enzyme activity.     

Polymorphism of adenosine deaminase in the pig: allelic variation in erythrocytes

Within the frame of our investigations on genetic variation of pig red cell enzymes, by means of enzymo-electrophoresis and spectrophotometric measurements, four kinds of adenosine deaminase phenotypic patterns were identified in haemolysates from 542 Belgian Landrace and 502 Pietrain pigs. Segregation data are consistent with the hypothesis that these phenotypes are determined by two codominant alleles ADA ^A and ADA ^B and a recessive silent allele ADA ^O, at an autosomal locus. Differences in gene frequencies between the two breeds are highly significant.     

Regulation of platelet adenylate cyclase by adenosine.

The stimulatory and inhibitory effects of adenosine on the adenylate cyclases of human and pig platelets were studied. Stimulation occurred at lower concentrations than did inhibition, and the stimulatory effect was prevented by methylxanthines. Stimulation by adenosine was immediate in onset and was reversible, under conditions when cyclic AMP formation was linear with respect to time and protein concentration. The stimulatory and inhibitory effects could be distinguished further by the use of various analogues of adenosine and could be prevented by adenosine deaminase. The data suggest that both stimulation and inhibition were due to adenosine itself and not one of its degradation products and that in the platelet preparation, neither formation nor degradation of adenosine during the adenylate cyclase incubation appreciably influenced measured activity. Stimulation by adenosine was additive with the effects of GMP-P(NH)P, and alpha- or beta-adrenergic stimulation, but was abolished by prostaglandin E1 or by NaF. Prostaglandin E1 and NaF increased the sensitivity of adenylate cyclase to inhibition by adenosine. The data suggest that guanyl-5'-yl-(beta-gamma-imino)diphosphate and/or adrenergic stimulation and adenosine exert their effects on adenylate cyclase by distinct mechanisms, but that prostaglandin E1 or F- and adenosine increase enzyme activity by mechanisms which may involve common intermediates in the coupling to adenylate cyclase.     

Polymorphism of red cell phosphoglucomutase, adenylate kinase and adenosine deaminase in a Polish population.

Genetic variants of PGM1, AK and ADA were studied in a sample of unrelated individuals from the Polish population. The gene frequencies observed are: PGM1/1: 0.715, AK1: 0.962 AND ADA1: 0.940.     

Polymorphism of erythrocyte phosphoglucomutase,adenylate kinase and adenosine deaminase in northern Thailand

Summary Phenotypes of the erythrocyte enzymes phosphoglucomutase (PGM) (n-587), adenylate kinase (AK) (n=695), and adenosine deaminase (ADA) (n=616) were determined by horizontal starch gel electrophoresis in Thai subjects from norther Thailand, mainly from the provinces of Chiang Mai and Lamphun. The following gene frequencies were calculated: PGM ₁ ¹ 0.7385 PGM ₁ ² 0.2487 PGM ₁ ⁶ 0.0102 PGM ₁ ⁷ 0.0026, AK ¹ 0.9950 AK ² 0.0050, ADA ¹ 0.9180 ADA ² 0.0820.The regular, apparently autosomal transmission of the PGM ₁ ⁶ and PGM ₁ ⁷ alleles was demonstrated in 7 families revealing sufficient data.

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Zusammenfassung Die Phänotypen der Erythrocytenenzyme Phosphoglucomutase (PGM) (n=587), Adenylatkinase (AK) (n=695), and Adenosindeaminase (ADA) (n=616) wurden mittles horizontaler Stärkegelelektrophorese bei Thailändern aus Nordthailand, hauptsächlich aus den Provinzen Chiang Mai und Lamphun, bestimmt. Auf Grund der Ergebnisse wurden die in der englischen Zusammenfassung angegebenen Genfrequenzen berechnet. Die regelmäßige, anschinend autosomale Vererbung der Allele PGM ₁ ⁶ und PGM ₁ ⁷ wurde in 7 Familien mit ausreichenden Daten nachgewiesen.

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