POLYNUCLEOTIDE-ADENOSINE GLYCOSIDASE ACTIVITY OF RIBOSOME-INACTIVATING PROTEINS - EFFECT ON DNA, RNA AND POLY(A)

Ribosome-inactivating proteins (RIP) are a family of plant enzymes for which a unique activity was determined: rRNA N-glycosidase at a speci fic universally conserved position, A(4324) in the case of rat ribosom es, Recently we have shown that the RIP from Saponaria officinalis hav e a much wider substrate specificity: they are actually polynucleotide :adenosine glycosidases, Here we extend studies on substrate specifici ty to most known RIP: 52 purified proteins, both type 1 (single-chain) and type 2 (two chain, an enzymatic chain and a lectin chain) were ex amined for adenine release on various substrates including RNAs from d ifferent sources, DNA, and poly(A), All RIP depurinated extensively DN A and some released adenine from all adenine-containing polynucleotide s tested. From experimental evidence the entire class of plant protein s, up to now called ribosome-inactivating proteins, may be classified as polynucleotide:adenosine glycosidases, The newly identified substra tes may be implicated in the biological role(s) of RIP.