Reduction of an aldehyde by a NADH/Zn2+ -dependent redox active ribozyme.

We report here the ability of an alcohol dehydrogenase (ADH) ribozyme to reduce a benzaldehyde. While the ribozyme was initially evolved in vitro based on the activity for the NAD+-dependent oxidation of the benzyl alcohol, we found that this ADH ribozyme is also capable of reducing the aldehyde in the presence of NADH and Zn2+. The rate acceleration gained by ribozyme catalysis was more than 6 orders of magnitude larger than the spontaneous reaction. Although the reversibility of phosphordiester and acyl transfer reactions catalyzed by ribozymes was known, that of other chemical reactions has not been well established. This study has demonstrated the reversibility of a hydride transfer chemistry catalyzed by the ADH ribozyme. Most interestingly, the ribozyme shares many features with the protein ADHs, e.g., reversibility and NADH/Zn2+ dependence.