A novel nucleoside hydrolase from Lactobacillus buchneri LBK78 catalyzing hydrolysis of 2′- O -methylribonucleosides.

2′-O-Methylribonucleosides (2′-OMe-NRs) are promising raw materials for nucleic acid drugs because of their high thermal stability and nuclease tolerance. In the course of microbial screening for metabolic activity toward 2′-OMe-NRs,Lactobacillus buchneriLBK78 was found to decompose 2′-O-methyluridine (2′-OMe-UR). The enzyme responsible was partially purified fromL. buchneriLBK78 cells by a four-step purification procedure, and identified as a novel nucleoside hydrolase. This enzyme,LbNH, belongs to the nucleoside hydrolase superfamily, and formed a homotetrameric structure composed of subunits with a molecular mass around 34 kDa.LbNH hydrolyzed 2′-OMe-UR to 2′-O-methylribose and uracil, and the kinetic constants wereKmof 0.040 mM,kcatof 0.49 s−1, andkcat/Kmof 12 mM−1 s−1. In a substrate specificity analysis,LbNH preferred ribonucleosides and 2′-OMe-NRs as its hydrolytic substrates, but reacted weakly with 2′-deoxyribonucleosides. In a phylogenetic analysis,LbNH showed a close relationship with purine-specific nucleoside hydrolases from trypanosomes. LbNH, a novel nucleoside hydrolase fromLactobacillus buchneriLBK 78 catalyzes 1'-hydrolysis reaction toward 2'-O-methyluridine to form 2'-O-methylribose and uracil as the degradation products. [ABSTRACT FROM PUBLISHER]