Supramolecular anchoring of metalloporphyrins in a protein is an attractive approach to the generation of artificial enzymes. Here, we employ the hydrophobic nanocage of single-ring mutant of bacterial GroEL protein for this purpose. We found that multiple monomeric hemin cofactors can be efficiently loaded into the protein nanocage. The as-prepared biohybrid possessed an oxidase-like catalytic activity and followed the typical Michaelis-Menten kinetics and a ping-pong mechanism in the H2O2-mediated oxidation of model substrates. In comparison with natural peroxidase, the artificial enzyme exhibited higher affinity for the model substrate. A simple and sensitive colorimetric method for the quantitative detection of H2O2 and glucose was also developed based on the artificial enzyme, with the detection limits determined to be 3.0 mu M for H2O2 and 5.0 mu M for glucose, respectively. The protein nanocage-based artificial enzyme is very flexible and is envisioned to be adapted readily for binding other metal complexes and catalysis of other reactions.