In the following sections, we present a description of the set, which we call MME55-mechanisms of metalloenzymes, containing 55 data points, including both barrier heights (BHs) and reaction energies (REs). This is followed by an analysis of the multireference character of the included models, and details on how the reference values were calculated. Finally we test a range of density functionals as well as the still popular second-order Møller-Plesset Perturbation Theory 77 (MP2), analyze their performance, and compare the results to other related benchmarking studies. We also reiterate the importance of London dispersion corrections for DFT methods, which has been stated in many studies including for bioorganic and bioinorganic systems, although the recommendation is still not always followed.