A thiamin-utilizing ribozyme decarboxylates a pyruvate-like substrate.

Area of Science:

• Biochemistry
• Molecular Biology
• Origin of Life Studies

Background:

• Vitamins are theorized as remnants of the RNA world, potentially involved in early RNA-mediated metabolism.
• Protein enzymes utilize cofactors like thiamin diphosphate (vitamin B1 derivative) for catalyzing challenging metabolic reactions, such as pyruvate decarboxylation.
• Ribozymes, or catalytic RNAs, could expand their reaction repertoire by harnessing vitamin cofactors, mimicking protein enzyme function.

Purpose of the Study:

• To investigate if ribozymes can utilize vitamin cofactors to perform metabolic reactions.
• To explore the potential role of RNA in early metabolic cycles through cofactor utilization.

Main Methods:

• A ribozyme capable of decarboxylating a pyruvate-based substrate (LnkPB) using free thiamin was selected from a pool of random-sequence RNAs.
• Thiamin conjugated to biotin was employed to isolate catalytically active RNA molecules.
• Analysis of a specific RNA sequence (clone dc4) and its guanosine adduct confirmed the decarboxylation product.

Main Results:

• A novel ribozyme was identified that utilizes free thiamin to catalyze the decarboxylation of a pyruvate-based substrate.
• The catalytic activity was confirmed through the analysis of reaction products, specifically a guanosine adduct.
• This represents the first discovery of a prototypic thiamin-utilizing ribozyme.

Conclusions:

• The findings demonstrate that ribozymes can indeed harness vitamin cofactors like thiamin for catalysis.
• This discovery supports the hypothesis that RNA played a significant role in orchestrating early metabolic pathways.
• The existence of such ribozymes has profound implications for understanding the transition from an RNA world to the modern biological systems.