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S. Tang, R.-g. Hu, W.-y. Liu, K.-c. Ruan

Non-Specific Depurination Activity of Saporin-S6, a Ribosome-Inactivating Protein, under Acidic Conditions

Among five ribosome-inactivating proteins tested only saporin-S6 could efficiently release the adenine from adenosine 20 of the synthetic oligoribonucleotide (SRD RNA) mimic of the sarcin/ricin domain of rat 28S rRNA with a K_m of 9?M and a k_cat of approximately 0.4 min^?1 at pH 7.6. The optimal pH for the depurination activity of saporin-S6 is 5.0. However, saporin-S6 lost its site-specificity of depurination on SRD RNA around the optimal pH. The non-specific depurination activity of saporin-S6 was dependent on the enzyme concentration and pH conditions. These results are valuable to understand the diversity and the depurination mechanism of ribosome-inactivating proteins.

Biological Chemistry, Walter de Gruyter

Print ISSN: 1431-6730
Volume: 381, 09/2000
Pages: 769 - 772

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