Please use this identifier to cite or link to this item: http://hdl.handle.net/10261/23759
Título : Hydrolysis of bis(5'-nucleosidyl) polyphosphates by Escherichia coli 5'-nucleotidase
Autor : Ruiz, Aníbal, Hurtado, Cipriano, Meireles Ribeiro, João, Günther Sillero, María A.
Fecha de publicación : Dec-1989
Editor: American Society for Microbiology
Resumen: Two enzymatic activities that split diadenosine triphosphate have been reported in Escherichia coli: a specific Mg-dependent bis(5'-adenosyl) triphosphatase (EC 3.6.1.29) and the bis(5'-adenosyl) tetraphosphatase (EC 3.6.1.41). In addition to the activities of these two enzymes, a different enzyme activity that hydrolyzes dinucleoside polyphosphates is described. After purification and study of its molecular and kinetic properties, we concluded that it corresponded to the 5'-nucleotidase (EC 3.1.3.5) that has been described in E. coli. The enzyme was purified from sonic extracts and osmotic shock fluid. From sonic extracts, two isoforms were isolated by chromatography on ion-exchange Mono Q columns; they had a molecular mass of about 100 kilodaltons (kDa). From the osmotic shock fluid, a unique form of 52 kDa was recovered. Mild heating transformed the 100-kDa isoform to a 52-kDa form, with an increase in activity of about threefold. The existence of a 5'-nucleotidase inhibitor described previously, which associates with the enzyme and is not liberated in the osmotic shock fluid, may have been responsible for these results. The kinetic properties and substrate specificities of both forms (52 and 100 kDa) were almost identical. The enzyme, which is known to hydrolyze AMP and uridine-(5')-diphospho-(1)-alpha-D-glucose, but not adenosine-(5')-diphospho-(1)-alpha-D-glucose, was also able to split adenosine-(5')-diphospho-(5)-beta-D-ribose, ribose-5-phosphate, and dinucleoside polyphosphates [diadenosine 5',5'''-P1,P2-diphosphate,diadenosine 5',5'''-P1,P3-triphosphate, diadenosine 5',5'''-P1,P4-tetraphosphate, and bis(5'-guanosyl) triphosphate]. The effects of divalent cations and pH on the rate of the reaction with different substrates were studied.
Descripción : 7 pages, 2 figures, 3 tables.
Versión del editor: http://jb.asm.org/cgi/content/short/171/12/6703
URI : http://hdl.handle.net/10261/23759
ISSN: 0021-9193
Citación : Journal of Bacteriology 171(12): 6703-6709 (1989)
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