RESUMEN
In the present paper physico-chemical properties of AMP-deaminase purified from human liver neoplasm-hepatocellular carcinoma (HCC) were investigated and compared with these obtained for the enzyme from normal, unaffected tissue.
Asunto(s)
AMP Desaminasa/química , Carcinoma Hepatocelular/enzimología , Neoplasias Hepáticas/enzimología , AMP Desaminasa/inmunología , Adenosina Monofosfato/química , Catálisis , Electroforesis en Gel de Poliacrilamida , Humanos , Concentración de Iones de Hidrógeno , Cinética , Hígado/patología , Necrosis/patología , Proteínas/químicaRESUMEN
AMP-deaminase from human liver was purified by two-step phosphocellulose chromatography, and SDS-PAG electrophoresis of the most active enzyme fraction eluted has been performed. The largest of the protein fragments revealed had a size (92 kDa) of an apparent full-size enzyme subunit, and reacted positively with antibodies produced against specific human ampd2 gene product. Three-day storage at cold room temperature modified significantly the electrophoretical pattern of the enzyme, evidencing continuous and progressive degradation of its structure. This is a first report evidencing the presence of apparent full-size form of human liver AMP-deaminase in preparation obtained from endogenous source.
Asunto(s)
AMP Desaminasa/química , AMP Desaminasa/aislamiento & purificación , Hígado/enzimología , Cromatografía Liquida , Electroforesis en Gel de Poliacrilamida , Humanos , Isoenzimas/química , Isoenzimas/aislamiento & purificación , Peso MolecularRESUMEN
AMP-deaminase from human term placenta was chromatographed on a phosphocellulose column and physico-chemical and immunological properties of the purified enzyme were investigated. At physiological pH 7.0, in the absence of regulatory ligands (control conditions) studied AMP-deaminase manifested sigmoid-shaped substrate saturation kinetics, with half-saturation parameter (S0.5) value of about 7 mM. Addition of important allosteric effectors (ATP, ADP or orthophosphate) modified kinetic properties of studied AMP-deaminase, influencing mainly the value of S0.5, parameter. Micromolar concentrations of stearylo-CoA inhibited potently the enzyme making it no longer sensitive towards 1 mM ATP-induced activation. SDS-PAGE electrophoresis of the purified enzyme revealed presence of 68 kDa protein fragment, reacting with anti-(human) liver AMP-deaminase antibodies. Experimental results presented indicate that 'liver type' of AMP-deaminase is an enzyme form present in human term placenta.
Asunto(s)
AMP Desaminasa/aislamiento & purificación , Placenta/enzimología , AMP Desaminasa/metabolismo , Regulación Alostérica , Western Blotting , Electroforesis en Gel de Poliacrilamida , Femenino , Humanos , Cinética , Embarazo , Especificidad por SustratoRESUMEN
AMP-deaminase (EC 3.5.4.6) is a key enzyme of nucleotide breakdown involved in regulation of adenine nucleotide pool in the liver. Mechanisms regulating activity of the enzyme are not completely elucidated, till now. In this paper experimental data indicating on the potential regulatory significance of changes in oligomeric structure of the enzyme are presented. SDS-PAG electrophoresis of human liver AMP-deaminase revealed the presence of three enzyme fragments. Only largest of them (the protein fragments weighing 68 kDa) reacted immunologically with anti- (human liver) AMP-deaminase antibodies. At physiological pH 7.0, in the absence of regulatory ligands, reaction catalysed by human liver AMP-deaminase was strongly dependent on enzyme concentration used, with half-saturation constant (S0.5) values increasing significantly with the degree of enzyme dilution. Preincubation with activated long-chain fatty acids--substances promoting dissociation of oligomeric enzymes, inhibited the activity of AMP-deaminase studied nearly completely. Gel filtration on Sepharose CL-6B column demonstrated existence of at least three active oligomeric forms of human liver AMP-deaminase. We postulate that oligomeric structure of the enzyme is a factor determining regulatory profile of AMP-deaminase studied.
Asunto(s)
AMP Desaminasa/metabolismo , Hígado/enzimología , AMP Desaminasa/química , AMP Desaminasa/aislamiento & purificación , Western Blotting , Cromatografía en Gel , Electroforesis en Gel de Poliacrilamida , Humanos , MasculinoRESUMEN
This article presents current views on the significance of homocysteine as a potential risk factor for atherosclerosis. The majority of numerous and extensive comparative examinations indicate that considerable hyperhomocysteinemia is an independent risk factor for the development of the premature atherosclerotic lesions. Because of that experts of the Nutrition Committee of American Heart Association published in 1999 the recommendations for the application of the preventive diet rich in vitamins B6, B12 and folic acid.
Asunto(s)
Arteriosclerosis/metabolismo , Homocisteína/metabolismo , Humanos , Factores de RiesgoAsunto(s)
AMP Desaminasa/genética , Proteínas Bacterianas/genética , Cardiomiopatía Dilatada/genética , Isoenzimas/genética , Mutación , N-Acetil Muramoil-L-Alanina Amidasa/genética , AMP Desaminasa/deficiencia , AMP Desaminasa/metabolismo , Biomarcadores/análisis , Cardiomiopatía Dilatada/enzimología , Humanos , Músculo Esquelético/enzimología , Pronóstico , Transcripción GenéticaAsunto(s)
Endotelinas/metabolismo , Secuencia de Aminoácidos , Animales , Ácido Aspártico Endopeptidasas/metabolismo , Canales de Calcio/metabolismo , Endotelina-1/metabolismo , Enzimas Convertidoras de Endotelina , Endotelinas/química , Endotelinas/genética , Humanos , Riñón/metabolismo , Metaloendopeptidasas , Músculo Liso Vascular/metabolismo , Fosforilación , Receptores de Endotelina/metabolismoAsunto(s)
AMP Desaminasa/metabolismo , Leiomioma/enzimología , Neoplasias Uterinas/enzimología , Útero/enzimología , AMP Desaminasa/aislamiento & purificación , Adenosina Difosfato/farmacología , Adenosina Trifosfato/farmacología , Cromatografía por Intercambio Iónico , Femenino , Humanos , Histerectomía , Cinética , Leiomioma/cirugía , Persona de Mediana Edad , Músculo Liso/enzimología , Fosfatos/farmacología , Valores de Referencia , Neoplasias Uterinas/cirugíaRESUMEN
Reactivity of sulfhydryl groups of human uterine smooth muscle AMP-deaminase with DTNB, and the effect of their chemical modification on kinetic and regulatory properties of the enzyme were investigated. (1), Approx. 7 and 5 sulfhydryl groups per mol of the enzyme have been shown to be accessible for DTNB (5,5'-dithiobis(2-nitrobenzoic acid)) titration in denaturated and native AMP-deaminase, respectively. (2), Titrated groups were not homogenous; some of them reacted with DTNB much faster than others. (3), The activity of the modified enzyme was very low, and the modified enzyme manifested unusual hyperbolic saturation kinetics with the substrate. (4), Exhaustive dialysis against a buffer containing 10 mM thioethanol reactivated the modified enzyme, and restored its original regulatory properties. Experimental results obtained indicate that modified sulfhydryl groups play a significant role in the maintenance of the proper, catalytically-efficient conformation of the enzyme.
Asunto(s)
AMP Desaminasa/química , Ácido Ditionitrobenzoico , Músculo Liso/enzimología , AMP Desaminasa/genética , AMP Desaminasa/metabolismo , Femenino , Humanos , Cinética , Conformación Proteica , Desnaturalización Proteica , Compuestos de Sulfhidrilo/química , Útero/enzimologíaRESUMEN
At pH 7.0 and physiological concentrations of the main regulatory ligands (ATP, ADP, orthophosphate), human uterine muscle AMP-deaminase follows a hyperbolic type of saturation kinetics with S0.5 parameter value about 2 mM. The enzyme is regulated by adenylate energy charge (AEC) variations, being the most active at the AEC value 0.5-0.6 or 0.5-0.7, depending on the size of the total adenine nucleotide pool. Long-chain acyl-CoA strongly inhibit activity of the enzyme, influencing mainly the maximum velocity of the reaction.
Asunto(s)
AMP Desaminasa/metabolismo , Adenosina Monofosfato/metabolismo , Ácidos Grasos/metabolismo , Músculo Liso/enzimología , Útero/enzimología , AMP Desaminasa/aislamiento & purificación , Femenino , Humanos , Concentración de Iones de Hidrógeno , CinéticaRESUMEN
AMP-deaminase from human uterine smooth muscle has been isolated, and properties of the enzyme were characterized. At pH 7.0, and in the presence of 100 mM potassium chloride the enzyme manifests a distinctly sigmoidal type of kinetics, with S0.5 parameter value about 12 mM. 1 mM ATP strongly activates the enzyme, and diminishes the value of S0.5 to 1.2 mM. In contrast to that 2.5 mM orthophosphate slightly inhibits the activity of AMP-deaminase studied and increases the S0.5 to about 14 mM. Similarly to ATP, orthophosphate does not influence the maximum velocity of the reaction. Electrophoresis in the presence of sodium dodecyl sulphate revealed that the molecular weight of human smooth muscle AMP-deaminase subunit is close to 37 kDa.