Lacadena García-Gallo, Francisco JavierMartínez Del Pozo, ÁlvaroValle LacadenaMartínez Ruiz, AntonioMancheño Gómez, José MiguelOñaderra Sánchez, MercedesGavilanes Franco, José Gregorio2024-04-232024-04-231998-03-06Lacadena Javier, Martı́nez del Pozo Alvaro, Lacadena Valle, Martı́nez-Ruiz Antonio, Mancheño José M, Oñaderra Mercedes and Gavilanes José G(1998), The cytotoxin α-sarcin behaves as a cyclizing ribonuclease, FEBS Letters, 424, doi: 10.1016/S0014-5793(98)00137-90014-57931873-346810.1016/s0014-5793(98)00137-9https://hdl.handle.net/20.500.14352/103372The hydrolysis of adenylyl(3PC5P)adenosine (ApA) and guanylyl(3PC5P)adenosine (GpA) dinucleotides by the cytotoxic protein K-sarcin has been studied. Quantitative analysis of the reaction has been performed through reversephase chromatographic (HPLC) separation of the resulting products. The hydrolysis of the 3P-5P phosphodiester bond of these substrates yields the 2P-3P cyclic mononucleotide; this intermediate is converted into the corresponding 3P-monophosphate derivative as the final product of the reaction. The values of the apparent Michaelis constant (KM), kcat and kcat/ KM have also been calculated. The obtained results fit into a twostep mechanism for the enzymatic activity of K-sarcin and allow to consider this protein as a cyclizing RNase. z 1998 Federation of European Biochemical Societies.engjournal articleopen access577.1Dinucleotide;Ribonucleolytic activity;Ribosome-inactivating protein;RibotoxinBioquímica (Química)2302 Bioquímica