Adenine nucleotide N-glycosidase activity of the A-chain of cinnamomin characterized by 1H-nuclear magnetic resonance.
Plant ribosome-inactivating proteins specifically cleave an N-glycosidic bond of a unique adenosine in the largest ribosomal RNA, releasing an adenine from ribosomes of different sources. Here, 1H-nuclear magnetic resonance is used to analyze the enzymatic products of the A-chain of cinnamomin, a type-II ribosome-inactivating protein (RIP) acting on the nucleotides in situ. The enzymatic activities of the RIP on nine nucleotides are compared. Cinnamomin A-chain can cleave the N-glycosidic bond and release an adenine base from adenine nucleotides except 5'-ATP; however, it cannot act on 5'-GMP, 5'-CMP, and 5'-UMP. The A-chain in the mixture of cinnamomin A- and B-chain exhibits higher activity toward adenine nucleotides than the A-chain alone does, suggesting that the B-chain can conformationally stabilize the A-chain. Intact cinnamomin also exhibits lower activity toward adenine nucleotides. However, cinnamomin B-chain and heat-denatured intact cinnamomin cannot hydrolyze all the tested nucleotides. We conclude that hydrolysis of the N-C glycosidic bond of nucleotide compounds by cinnamomin A-chain has a base preference, and the negatively charged phosphate group(s) reduces the recognition ability of the A-chain to adenine nucleotide.
Shanghai Institute of Biochemistry, Chinese Academy of Sciences.
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Xu
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Li
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Wu
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Liu
D000227:Adenine Nucleotides / Q000378:metabolism*; D020418:Algal Proteins; D006026:Glycoside Hydrolases / Q000378:metabolism*; D008970:Molecular Weight; D019906:Nuclear Magnetic Resonance, Biomolecular; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D054790:Ribosome Inactivating Proteins, Type 2; D013379:Substrate Specificity
D000227:Adenine Nucleotides; D020418:Algal Proteins; D011506:Proteins; D054790:Ribosome Inactivating Proteins, Type 2; C061930:cinnamomin, Phytophthora cinnamomi; D006026:Glycoside Hydrolases