Phytoene desaturase (lycopene-forming) Phytoene desaturase (lycopene-forming) Phytoene desaturase (lycopene-forming) (CrtI, "four-step phytoene desaturase") (, "15-cis-phytoene:acceptor oxidoreductase (lycopene-forming)") are enzymes found in archaea, bacteria and fungi that are involved in carotenoid biosynthesis. They catalyze the conversion of colorless 15-"cis"-phytoene into a bright red lycopene in a biochemical pathway called the poly-trans pathway. The same process in plants and cyanobacteria utilizes four separate enzymes in a poly-cis pathway. Bacterial phytoene desaturases were shown to require FAD as a cofactor for their function. During the chemical reaction in total four additional double bonds are introduced into phytoene: In 2000 it was discovered that the gene insertion
Self colour the tip. The term can also be used to distinguish between colour and pattern; patterns are unpigmented areas with pink skin and white hair. In this definition, an animal has only one self-colour, which is the sum effect of all the genes acting on the pigment. For example, a black and tan piebald Dachshund has patterns (piebald) and self-colours (black and tan). Self colour A self colour refers to the top coat colouration of several domestic animals, such as dogs, pet rodents and cats. It refers to hairs of a uniform shade, with no banding or tipping of another colour.