Comparative Quantitative Analysis of Kcat Modulation in Laccases Engineered by Rational, Semi-Rational, and Directed Evolution Approaches

Laccases are biotechnologically valuable enzymes that oxidize phenolic compounds across multiple industries. Their kinetic parameters Km, kcat, and redox potential (E°)—vary with substrate, origin, sequence, and structure, all of which influence electron transfer efficiency toward the trinuclear copper center. Improving kcat and E° is therefore essential for industrial applications. This review analyzes 143 studies, compiling 244 kcat values for ABTS, 125 for 2,6-dimethoxyphenol (2,6-DMP), and 53 for syringaldazine (SGZ). A high-performing laccase was defined by the upper quartile (Q3) of reported values: kcat ≥ 798, 293, and 140 s−1 for ABTS, 2,6-DMP, and SGZ, respectively. Among 36 mutagenesis studies—classified as rational, semi-rational, or directed evolution—directed evolution combined with rational and semi-rational design yielded the greatest improvements, reaching kcat values up to 1328.8 s−1 for ABTS. While Km data are compiled to assess catalytic efficiency, cross-study analysis reveals no consistent directional trend in substrate affinity among engineered variants. In contrast, kcat shows systematic improvement across diverse systems and substrates, establishing it as the primary performance metric for evaluating laccase engineering outcomes.