J. Biol. Chem., Vol. 261, Issue 2, 592-598, Jan, 1986
Activity of acid deoxyribonuclease towards diastereoisomers of thymidyl 3'-(4-nitrophenyl phosphorothioate). Stereochemistry of transnucleotidylation reaction
B Uznanski, W Niewiarowski and WJ Stec
The (Rp)- and (Sp)-diastereoisomers of thymidyl 3'-(4-nitrophenyl
phosphorothioate) (1) were found to act as unusual substrates for acid
deoxyribonuclease (DNase II). Instead of the expected thymidine 3'-
phosphorothioate, the product resulting from the reaction of (Rp)-1
catalyzed by DNase II was identified as (Sp, Rp)-thymidyl (3'- 5')thymidyl
phosphorothioate 3'-(4-nitrophenyl phosphorothioate), while that from
(Sp)-1 has been recognized as a 10:1 mixture of (Sp, Rp)- thymidyl
(3'-5')thymidyl phosphorothioate 5'-(4-nitrophenyl phosphorothioate) and
(Rp, Sp)-thymidyl (3'-5')-thymidyl phosphorothioate 3'-(4-nitrophenyl
phosphorothioate), respectively. Both types of transnucleotidylations were
found to occur with retention of configuration at phosphorus.
Stereochemical results may be interpreted in terms of two step mechanisms
involving the formation of the intermediate, covalent substrate enzyme
complexes.