Effects of protein-modifying reagents on an isoenzyme of potato apyrase |
| |
Authors: | M Antonieta Valenzuela Guillermo Del Campo Eugenio Marín and Aída Traverso-Cori |
| |
Institution: | Laboratory of General Biochemistry, Faculty of Chemical Sciences, University of Chile, Casilla 233, Santiago 1, Chile |
| |
Abstract: | Treatment of an isoenzyme of potato apyrase of high adenosine triphosphatase/adenosine diphosphatase (ATPase/ADPase) ratio with iodine, N-acetylimidazole or tetranitromethane inactivates the ATPase activity of this enzyme faster than its ADPase activity. There was protection by substrates with the two last-named substances. This and the appearance of nitrotyrosine suggests the participation of tyrosyl residues in both enzymic activities of potato apyrase. The participation of thiol groups is excluded by the insensitivity of apyrase to p-chloromercuribenzoate. Also, 2-hydroxy-5-nitrobenzyl bromide or carboxymethylation produce the same rate of inactivation of ATPase and ADPase activities. Substrates protect both activities from inactivation. Hydrogen peroxide and photo-oxidation inactivate ATPase activity faster than ADPase activity. There is no protection by substrates. Analysis of pH effects on Vmax. and Km suggest different pK values for the amino acid residues at the ATP and ADP sites. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|