Unusual peroxidase activity of a myoglobin mutant with two distal histidines

By retaining the native distal His64 in sperm whale myoglobin (Mb), a second distal histidine was engineered in Mb by mutating Leu29 to His29. The resultant mutant of L29H Mb exhibits an unusual enhanced peroxidase activity with a positive cooperativity in comparison to that of wild type Mb. The new enzyme with two cooperative distal histidines has not been found in native peroxidase, which emphasizes a creation of the rational protein design.