Menaquinol oxidase (H<sup>+</sup>-transporting) (, cytochrome aa3-600 oxidase) is an enzyme with systematic name menaquinol:O2 oxidoreductase (H+-transporting). This enzyme catalyses the following chemical reaction
Cytochrome aa3-600, one of the respiratory oxidases from Bacillus subtilis, is a member of the heme-copper family of oxygen reductases.