title: Mung bean (Phaseolus aureus) nuclease. A mechanistic investigation of the DNA-cleavage reaction using a dinucleoside phosphorothioate.
abstract: Mung-bean (Phaseolus aureus) nuclease has been found to cleave the Sp diastereoisomer of 5'-O-thymidyl 3'-O-(2'-deoxyadenosyl)phosphorothioate, (Sp)-d[Ap(S)T], in 18O-labelled water with inversion of configuration at phosphorus to give (Sp)-thymidine 5'-[16O, 18O]phosphorothioate, the stereochemistry of which was deduced by methylation to (Rp,Sp)-thymidine 5'-S-methyl-O-methyl-[16O,18O]phosphorothioate and 31P-n.m.r. analysis. This result is consistent with a mechanism involving a direct 'in-line' attack of water on DNA for the nuclease-catalysed reaction without the involvement of a covalent nucleotidylated-enzyme intermediate.
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000378:metabolism*; D004720:Endonucleases / Q000378:metabolism*; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D008956:Models, Chemical; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000378:metabolism*; D015719:Single-Strand Specific DNA and RNA Endonucleases; D013237:Stereoisomerism; D013873:Thionucleotides / Q000378:metabolism*
chemical_list: D009838:Oligodeoxyribonucleotides; D013873:Thionucleotides; D004247:DNA; C052815:5'-O-thymidyl 3'-O-(2'-deoxyadenosyl) phosphorothioate; D004720:Endonucleases; D015719:Single-Strand Specific DNA and RNA Endonucleases