title: The enzymatic hydrolysis of the phosphate ester bond in some thionucleotides.
abstract: We prepared the 5'- and 3'-O-phosphorothioate esters of the antitumor agent O2 : 2'-anhydro-1-beta-D-arabinosylcytosine. We also included in this study esters of 2'-thio-2'-deoxycytidine, namely, 2'-S-dCyd-2' : 3'-P, 2'-S-dCyd-2'-P, and 2'-S-dCyd-3'-P, along with natural nucleotides. These compounds were subjected to the action of Escherichia coli alkaline phosphatase, potato acid phosphatase, and bovine pancreatic ribonuclease A. The data were analyzed by Lineweaver-Burk plots to obtain Km and KI values. Only 2'-S-dCyd-2'-P was a substrate for alkaline phosphatase; the anhydro-araCyt phosphorothioates were good competitive inhibitors, while 2'-S-dCyd-3'-P did not associate with the enzyme. Acid phosphatase hydrolyzed all four monoesters investigated, including the S-phosphorothioate. The cyclic phosphorothioate, 2'-S-dCyd-2' : 3'-P was neither hydrolyzed by, nor associated with, ribonuclease A. ORD spectroscopy was also used in an attempt to relate the structural features of analogs to the peculiarity of their hydrolysis.
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism; D003504:Ancitabine / Q000031:analogs & derivatives / Q000378:metabolism; D003561:Cytarabine / Q000378:metabolism; D003845:Deoxycytosine Nucleotides / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D009905:Optical Rotatory Dispersion; D012260:Ribonucleases / Q000378:metabolism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013873:Thionucleotides / Q000378:metabolism*
chemical_list: D003845:Deoxycytosine Nucleotides; D013873:Thionucleotides; D003561:Cytarabine; D003504:Ancitabine; D012260:Ribonucleases; D000469:Alkaline Phosphatase; D000135:Acid Phosphatase