IMP-GMP 5 '-nucleotidase from rat brain: Activation by polyphosphates

• Type: Article in International Scientific Journal
• Date: 1998

Authors

Marques, AFP (Author) FFUP; Teixeira, NA (Author) FFUP; Gambaretto, C (Author) Other; Sillero, A (Author) Other; Sillero, MAG (Author) Other

Journal

Title: Journal of Neurochemistry

Vol. 71

Pages: 1241-1250

ISSN: 0022-3042

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 23 Citations

Scopus - 27 Citations

Scientific classification

FOS: Medical and Health sciences > Basic medicine

Other information

Authenticus ID: P-001-77B

Abstract (EN): IMP-GMP 5'-nucleotidase has been purified to homogeneity from total rat brain extracts. This preparation showed a unique band (M-r 54,000 +/- 1,509) in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme presented the following properties: optimal pH value, 6.5-6.8; relative velocity measured in the presence of MgCl2, MnCl2, CoCl2, and NiCl2 (2 mM), 100, 60, 11, and <1, respectively; preferred substrates, IMP and GMP; and activation constant (K-a) found for Ap(4)A, Ap(5)A, and Ap(6)A, 83 +/- 38, 77 +/- 32, and 57 +/- 12 mu M, respectively. Under assay conditions where activation by Ap(4)A was fivefold, the activation produced by dinucleotides was as follows: Ap(4)G (4.0), Ap(4)I (2.9), Ap(4)X (3.3), Ap(4)C (0.7), Ap(4)U (1.1), Ap(4)epsilon A(1.5), Ap(4)ddA(1.7), Gp(4)G (2.2), Ap(3)A (1.1), and Ap(2)A (1.2). Polyphosphates P-18, P-.19, P-20, and P-35, were activators of the reaction with calculated K-a values of 3.5 +/- 0.5, 0.9 +/- 0.2, 0.6 +/- 0.2, and 1.3 +/- 0.5 mu M, respectively. The following compounds, at 0.1 mM, were effecters of the phosphotransferase reaction producing the fold activation indicated: Ap(4)A (8.3), Ap(5)A (10.2), Ap(6)A (10.1), Ap(4)G (7.7), Ap(4)X (7.6), Ap(4)U (2.1), glycerate 2,3-bisphosphate (3.9), and unpurified P-15 (7.6). Two enzyme forms of IMP-GMP 5'-nucleotidase were detected when the extracts from rat tissues or from the crustacean Artemia were subjected to chromatography on a Dyematrex Green A column. The ratio of the hydrolytic activities under both peaks (peak I/peak II) was as follows: brain (1.5), heart (1.9), liver (1.6), lung (2.0), testis (3.8), and Artemia cysts (2.0).

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10