Functional cloning, heterologous expression, and purification of two different N-deoxyribosyltransferases from Lactobacillus helveticus.

摘要: Lactobacillus helveticus contains two types of N-deoxyribosyltransferases: DRTase I catalyzes the transfer 2'-deoxyribose between purine bases exclusively whereas II is able to pyrimidine or and bases. An Escherichia coli strain, auxotrophic for guanine unable use deoxyguanosine as source guanine, was constructed clone corresponding genes. By screening a genomic bank production L. ptd ntd genes coding II, respectively, were isolated. Although have no sequence similarity, deduced polypeptides display 25.6% identity, with most residues involved in substrate binding active site nucleophile Glu-98 being conserved. Overexpression purification proteins shows that specific purines preference deoxyinosine (dI) > deoxyadenosine donor substrates has strong pyrimidines base acceptors. Purine analogues acceptor both enzymes. Comparison activities dI hypoxanthine colocalization add suggest role metabolism dI.