title: Calcium-dependent endoribonuclease of Trypanosoma brucei has a base-preferential affinity to adenylate.
abstract: The substrate specificity of a calcium-dependent endoribonuclease of Trypanosoma brucei cytoplasm has been further determined. The actions of the enzyme on transfer RNA, ribosomal RNA and various synthetic polyribonucleotides indicate that the enzyme degrades double-stranded as well as single-stranded RNAs; while it preferentially hydrolyses polyribonucleotides having adenylic acid residues, and has a pronounced preference for poly (adenylic acid). Its apparent Michaelis constant (Km) values using different substrates also suggest a base-preferential affinity of the enzyme to adenylate. The relative activity of the ribonuclease against homopolyribonucleotides is poly(A) greater than poly(U) greater than poly(C); while poly(G) is completely resistant to the activity. Poly(A) segments on poly(A)-rich RNA are selectively hydrolyzed by the endoribonuclease. A possible implication of this enzyme in the post-transcriptional modification and turnover of mRNA molecules is suggested.
authors.forename: G O
authors.initials: GO
authors.lastname: Gbenle
mesh_terms: D000249:Adenosine Monophosphate / Q000378:metabolism*; D000818:Animals; D003593:Cytoplasm / Q000378:metabolism; D004722:Endoribonucleases / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D011061:Poly A; D011131:Polyribonucleotides / Q000378:metabolism; D012313:RNA; D012333:RNA, Messenger; D013379:Substrate Specificity; D014346:Trypanosoma brucei brucei / Q000201:enzymology*
chemical_list: D011131:Polyribonucleotides; D012333:RNA, Messenger; D011061:Poly A; D000249:Adenosine Monophosphate; D012313:RNA; D004722:Endoribonucleases