The oxygen incorporated need not be derived from O2 with NADH or NADPH as one donor, and incorporation of one atom o oxygen into the other donor.

The oxygen incorporated need not be derived from O. This family of enzymes includes tryptophan 2,3-dioxygenase (TDO, also known as tryptophan oxygenase and L-tryptophan pyrrolase) and indoleamine 2,3-dioxygenase (IDO, also known as tryptophan pyrrolase).

Experiments show that the 6a oxygen of glycinol is derived from molecular oxygen.

The oxygen is derived from the hot waters out of which the emeralds crystallized, and each of the few known mines in the world seems to have had water with different isotope ratios.

The oxygen that is inserted into the C-H bond is usually derived from atmospheric oxygen (O2).

The oxygen incorporated need not be derived from O. The systematic name of this enzyme class is 3,4-dihydroxy-L-phenylalanine:oxygen 2,3-oxidoreductase (recyclizing).