The Hexose oxidase (of the family oxidoreductases) has two substrates called D-glucose and O2 (Oxygen), the third most abundant element in the universe by mass and constitutes 20.95% of the Earth's atmosphere.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with oxygen as acceptor. Thus, the two substrates of this enzyme are D-glucose and O2, whereas its two products are D-glucono-1,5-lactone and H2O2. After hydrogen and helium, oxygen is the third-most abundant element in the universe by mass. Diatomic oxygen gas constitutes 20.95% of the Earth's atmosphere. 
