Chalcone isomerase

PDB 1jep EBI

Chalcone isomerase (CHI) is an enzyme that plays a crucial role in the flavonoid biosynthesis pathway, which is significant for plant coloration, UV protection, and resistance against pathogens. CHI catalyzes the stereospecific isomerization of chalcones to their corresponding (2S)-flavanones, a key step in the production of various flavonoids and isoflavonoids. This enzyme is found across a wide range of plant species, highlighting its importance in plant biochemistry and physiology.

Function

CHI facilitates the conversion of chalcones, which are open-chain flavonoids, into the cyclic (2S)-flavanones. This reaction is critical in the flavonoid biosynthesis pathway, leading to the production of important compounds such as anthocyanins, flavonols, and isoflavonoids. These compounds are involved in a multitude of plant functions, including pigmentation, UV filtration, symbiotic nitrogen fixation, and defense against herbivores and pathogens.

Structure

The structure of CHI is characterized by a barrel fold, which is common among proteins that bind small ligands. This fold allows for the specific binding of chalcone substrates and facilitates their isomerization to flavanones. The active site of CHI is typically composed of residues that are highly conserved across different plant species, indicating the evolutionary importance of this enzyme's function.

Evolution

CHI is considered to have evolved early in the plant lineage, given its widespread presence across various plant species. The enzyme's critical role in flavonoid biosynthesis suggests that it has been a key factor in the adaptation of plants to their environments, particularly in response to UV radiation and pathogen attack.

Biotechnological Applications

Due to its role in flavonoid biosynthesis, CHI has been a target of biotechnological interest. Manipulation of CHI expression in plants can lead to altered flavonoid profiles, which can enhance plant colors, improve disease resistance, and increase antioxidant levels. Such modifications have potential applications in agriculture, horticulture, and the production of dietary supplements.

See Also

• Flavonoid biosynthesis
• Enzyme
• Plant physiology
• Biochemistry

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