Inconsistencies and ambiguities in calculating enzyme activity: The case of laccase.

Laccase is a key enzyme in the degradation of lignin by fungi. Reports indicate that the activity of this enzyme ranges from 3.5 to 484,000 U L(-1). Our aim was to analyze how laccase activity is calculated in the literature, and to determine statistically whether variations in activity are due to biological properties or to inconsistencies in calculation. We found a general lack of consensus on the definition of enzyme activity, and enzymes are sometimes characterized in terms of reaction rate and specific activity. Moreover, enzyme activity is calculated using at least seven different equations. Therefore, it is critical to standardize the calculation of laccase activity in order to compare results directly.