Retinal-producing oxygenase enzyme, molecular model. This enzyme, an oxygenase, plays a role in the production and metabolism of retinal and other apocarotenoids. Retinal is the chemical basis of vision in animals. This enzyme has four protein chains, indicated here by the colours. It is also referred to as apocarotenoid-cleaving oxygenase. This example is from a Synechocystis cyanobacterium.