ID   4.6.1.23
DE   ribotoxin.
AN   alpha-sarcin.
AN   rRNA endonuclease.
CA   a 28S rRNA containing guanosine-adenosine pair + H2O = an [RNA fragment]-
CA   3'-adenosine-3'-phosphate + a 5'-a hydroxy-guanosine-3'-[RNA fragment].
CC   -!- Ribotoxins are rRNA endonucleases that catalyze the cleavage of the
CC       phosphodiester bond between guanosine and adenosine residues at one
CC       specific position in 28S rRNA.
CC   -!- The enzyme secreted by Aspergillus giganteus specifically cleaves rat
CC       28S rRNA between G(4325) and A(4326) and displays cytotoxic activity
CC       toward animal cells.
CC   -!- It can also act on bacterial rRNAs.
CC   -!- The enzyme catalyzes a two-stage endonucleolytic cleavage.
CC   -!- The first reaction produces 5'-hydroxy-phosphooligonucletides and
CC       3'-phosphooligonucleotides ending with 2',3'-cyclic phosphodiester,
CC       which are released from the enzyme.
CC   -!- The enzyme then hydrolyzes these cyclic compounds in a second
CC       reaction that takes place only when all the susceptible
CC       3',5'-phosphodiester bonds have been cyclised.
CC   -!- The second reaction is a reversal of the first reaction using the
CC       hydroxyl group of water instead of the 5'-hydroxyl group of ribose.
CC   -!- The overall process is that of a phosphorus-oxygen lyase followed by
CC       hydrolysis to form the 3'-nucleotides.
CC   -!- Formerly EC 3.1.27.10.
DR   C0HLG3, RNAG_CYCAE ;  P00655, RNAS_ASPGI ;
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