Which enzyme plays an important role in the conversion of arachidonic acid to leukotrienes?

The enzyme is lipoxygenase.

Lipoxygenase is a variety of enzymes that can cause oxidation of fatty acids. There are several varieties of lipoxygenases, some of which are present in plants. They are involved in the formation of white blood cells that are involved in some severe allergic reactions (anaphylaxis). It is based on this knowledge that antiallergic drugs have been developed to inhibit the activity of lipoxygenase, including reducing inflammatory reactions.

Leukotrien are named thus because they were discovered in leucocytes and that they are unsaturated lipids with 3 conjugated double bonds (trienes) and 20 carbon atoms

it is a limiting nutrient limited by a single nutrient in the ecosystem, & the single goes very slow.