CAN A SUBSTRATE ENANTIOMER BE A SUBSTRATE FOR THE SAME ENZYME

The substrate specificity of DNA polymerases and some other enzymes in volved in DNA biosynthesis toward L- and D-enantiomer pairs of nucleos ides and nucleotides was studied. As a result, an explanation was prop osed according to which the enzymes may use both D- and L-substrates i f the substrate fragment carrying an asymmetric atom (or atoms) does n ot interact in a specific way with appropriate enzymes. The facts accu mulated and their explanations seem to be a strong argument in favor o f the hypothesis proposed earlier [A: A. Krayevsky, N. B. Dyatkina, an d M. K. Kukhanova, Nucleosides and Nucleotides, 14, 735-738 (1995)], a ccording to which some enzymes, first of all viral reverse transcripta ses, bind their substrates by interacting only with the nucleic base a nd the triphosphate residue. A model of the active center of replicati ve DNA polymerase is proposed.