# Characterising Complex Enzyme Reaction Data

## TL;DR

This paper explores how enzyme classifications can be linked to multiple reactions, revealing complexities in enzyme function that could improve enzyme annotation and evolutionary studies.

## Contribution

The paper reveals that nearly one-third of EC numbers are linked to multiple reactions, including different types of bond changes.

## Key findings

- Almost one-third of EC numbers are associated with multiple reactions in secondary databases like KEGG.
- Some EC numbers correspond to reactions that catalyze different types of bond changes.
- This complexity suggests a need for updated enzyme classification and annotation methods.

## Abstract

The relationship between enzyme-catalysed reactions and the Enzyme Commission (EC) number, the widely accepted classification scheme used to characterise enzyme activity, is complex and with the rapid increase in our knowledge of the reactions catalysed by enzymes needs revisiting. We present a manual and computational analysis to investigate this complexity and found that almost one-third of all known EC numbers are linked to more than one reaction in the secondary reaction databases (e.g. KEGG). Although this complexity is often resolved by defining generic, alternative and partial reactions, we have also found individual EC numbers with more than one reaction catalysing different types of bond changes. This analysis adds a new dimension to our understanding of enzyme function and might be useful for the accurate annotation of the function of enzymes and to study the changes in enzyme function during evolution.