Estudo comparativo do efeito da asparagina sobre a glutamato desidrogenase de diferentes orgãos de anfibios e de rato

AUTOR(ES)
DATA DE PUBLICAÇÃO

1978

RESUMO

The L-glutamate dehydrogenase CGDH) [L-glutama teNAD(P) oxidoreduetase ( deaminating) B.C.1.4.1.2-4] a key regulatory enzyme of NH3, glutamate and alfa-ketoglu tare metabolism, was extracted with 0,1% cetyltrimethy1 ammonium bromide from liver, kidney and heart of the amphibians Bufo paracnemis and Rana catesbeiana and rat. This enzyme catalyses the reversible reaction of oxidative deaminating of the glutamate NAD(P) dependent. Asparagine (Asn) at concentration from 1 to 50 mM cause a dramatic increase on GlDH activities, i.e., when the enzyme catalyses the reaction on the presence of NADH and alfa-ketoglutarate, from 10 to over 90 times, depending on the enzyme origin. However, no effect was observed on G2DH, i.e., when the enzyme catalyzes the reaction on the presence of NAD+ and glutamate. The effect of Asn is different with respect on animal organs. The B. paracnemis, R. catesbeiana and rat heart GlDH is much more affected by Asn 50 mM then GlDH from kidney and liver of same animal. The optimum pH of GlDH reaction is increased about 0.5 pH unit by the presence of Asn 50 mM. This fact may suggest that the Asn could change the dissociation contant of some ion group of the enzyme with importance to enzymatic reaction. The B. paracnemis, R. catesbeiana and rat liver, kidney and heart GlDH has the characteristic of changing the enzymatic activity exponentially by the changing of the enzyme concentration. This characteristic is related with the state of protein aggregation that is caused by the increase of enzime concentration. On the other hand, GlDH has a linear dependence of the enzyme activity in function of enzyme concentration when Asn 50 mM is present during the enzymatic reation. ADP 0.1 mM does not increase the B. paracnemis heart GlDH, at our experiment conditions of low enzyme con centrations, but increases about 20% the effect of Asn on that enzyme. Glutamine 50 mM does shown any effect on B. paracnemis heart GlDH, but decreases about 20% the effect of Asn on that enzyme.

ASSUNTO(S)

bioquimica catalisadores enzimas

ACESSO AO ARTIGO

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