Polynucleotide: adenosine glycosidase activity of saporin-L1: effect on DNA, RNA and poly(A).
The ribosome-inactivating proteins (RIPs) are a family of plant enzymes for which a unique activity has been determined: rRNA N-glycosidase, which removes adenine at a specific universally conserved position (A4324 in the case of rat ribosomes). Here we report that saporin-L1, a RIP from the leaves of Saponaria officinalis, recognizes other substrates, including RNAs from different sources, DNA and poly(A). Saporin-L1 depurinated DNA extensively and released adenine from all adenine-containing polynucleotides tested. Adenine was the only base released from DNA or artificial polynucleotides. The characteristics of the reactions catalysed by saporin-L1 have been determined: optimal pH and temperature, ionic requirements, and the kinetic parameters Km and kcat. The reaction proceeded without cofactors, at low ionic strength, in the absence of Mg2+ and K+. Saporin-L1 had no activity towards various adenine-containing non-polynucleotide compounds (cytokinins, cofactors, nucleotides). This plant protein may now be classified as a polynucleotide: adenosine glycosidase.
Dipartimento di Patologia sperimentale dell'Università degli Studi di Bologna, Italy.
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L
Barbieri
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Valbonesi
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P
Gorini
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Pession
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Stirpe
D000818:Animals; D001665:Binding Sites; D004247:DNA / Q000378:metabolism*; D000922:Immunotoxins; D007700:Kinetics; D009699:N-Glycosyl Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D010944:Plants; D012313:RNA / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D054788:Ribosome Inactivating Proteins; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins; D013379:Substrate Specificity
D000922:Immunotoxins; D010940:Plant Proteins; D012333:RNA, Messenger; D054789:Ribosome Inactivating Proteins, Type 1; D012313:RNA; D004247:DNA; D009699:N-Glycosyl Hydrolases; D054788:Ribosome Inactivating Proteins; D000076985:Saporins