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 buchneri LBK78 was found to decompose 2′-O-methyluridine (2′-OMe-UR). The enzyme responsible was partially purified from L. buchneri LBK78 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 were K m of 0.040 mM, k cat of 0.49 s −1 , and k cat /K m of 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 from Lactobacillus buchneri LBK 78 catalyzes 1'-hydrolysis reaction toward 2'-O-methyluridine to form 2'-O-methylribose and uracil as the degradation products.