Ommochrome

Ommochrome is a class of biological pigments that play a significant role in the coloration of various organisms, particularly insects and crustaceans. These pigments are derivatives of tryptophan, an essential amino acid, and are responsible for a range of colors from yellow to red, brown, and even black. Ommochromes are not only important for pigmentation but also involved in photoprotection, vision, and possibly antioxidative processes.

Biosynthesis

The biosynthesis of ommochromes involves several enzymatic steps starting from tryptophan. The initial step is the conversion of tryptophan to kynurenine, catalyzed by the enzyme tryptophan-2,3-dioxygenase. Kynurenine is then further modified through various pathways to produce different types of ommochromes, such as ommins and xanthommatin. The specific pathway and the resulting ommochrome type depend on the organism and the tissue in which these pigments are synthesized.

Function

Ommochromes have multiple functions in organisms:

• Pigmentation: They contribute to the coloration of the exoskeleton, eyes, and other tissues in insects and crustaceans. This pigmentation can serve various purposes, including camouflage, sexual attraction, and signaling.

• Vision: In the compound eyes of insects, ommochromes are involved in filtering light and protecting photoreceptor cells from UV damage. They help in the adaptation of vision to different light conditions.

• Antioxidant activity: There is evidence suggesting that ommochromes can act as antioxidants, protecting cells from oxidative stress.

Distribution

Ommochromes are predominantly found in the eyes and integument of insects and crustaceans. However, their presence has also been detected in other invertebrates, indicating a broader distribution among animal taxa.

Research and Applications

Research on ommochromes has implications in various fields, including evolutionary biology, ecology, and biotechnology. Understanding the biosynthesis and function of these pigments can shed light on the evolutionary adaptations of organisms to their environments. Additionally, ommochromes have potential applications in the development of natural dyes and antioxidants.

See Also

• Pigmentation
• Tryptophan
• Kynurenine
• Antioxidant