Y.-Z. Xu, Y.-J. Li, H.-Y. Hu, R.-g. Hu, H. Wu, W.-Y. Liu
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.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 381, 06/2000
Pages: 447 - 451
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