RESEARCH: VIOLAXANTHIN-DEEPOXIDASE-STRUCTURE
FOLDING PROJECT #19333 PROFILE

Plants change how they photosynthesize based on light. A process called the xanthophyll cycle helps them deal with strong light by using an enzyme called VDE. VDE becomes active in acidic conditions and works by transforming violaxanthin into zeaxanthin, which protects plants from excess energy. The project relates to how the structure of VDE changes depending on pH to carry out this important function.

Note: This TLDR is a simplication and may not be 100% accurate.

To adapt to shifting lighting conditions, plants modify their photosynthetic activity.

The xanthophyll cycle, in which the carotenoid violaxanthin is transformed into zeaxanthin in strong light, plays a key role in controlling photosynthesis.

This process activates the disposal of excess absorbed energy as heat and the scavenging of reactive oxygen species.

When photosynthetic electron transport exceeds the capacity of assimilatory reactions, violaxanthin deepoxidase (VDE), the enzyme responsible for zeaxanthin synthesis, is activated by the acidification of the thylakoid lumen.

At neutral pH, VDE is a soluble and inactive enzyme, but at acidic pH, it attaches to the thylakoid membrane where it binds its substrate.

Ascorbate is used by VDE as a cosubstrate as well, and its pH-dependent Km may indicate a preference for ascorbic acid.

At neutral and acidic pH, we established the structures of the central lipocalin domain of VDE (VDEcd).

VDEcd is monomeric and has its active site blocked by a lipocalin barrel at neutral pH.

The barrel unwinds and the enzyme emerges as a dimer during acidification.

The two violaxanthin beta-ionone rings may be deep oxidized simultaneously in two channels that connect the two active sites of the dimer, giving VDE an ideal example of an asymmetric enzyme's adaptation to its symmetric substrate.

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Photosynthesis

The process by which plants convert light energy into chemical energy.

Photosynthesis is how plants use sunlight, water, and carbon dioxide to create their own food (sugar). This process releases oxygen as a byproduct. It's essential for life on Earth because it provides the oxygen we breathe and the food we eat.

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Xanthophyll Cycle

A cycle of biochemical reactions involving carotenoid pigments in plants.

The xanthophyll cycle is a crucial process in plants that helps them protect themselves from damage caused by excess light. It involves the conversion of different carotenoid pigments like violaxanthin and zeaxanthin, which act as antioxidants to absorb harmful light energy.

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Violaxanthin

A type of carotenoid pigment found in plants.

Violaxanthin is a yellow-red pigment found in plants that plays a key role in the xanthophyll cycle. It helps protect plants from damage caused by excess light energy.

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Zeaxanthin

A type of carotenoid pigment found in plants.

Zeaxanthin is a red-orange pigment found in plants that plays a key role in the xanthophyll cycle. It helps protect plants from damage caused by excess light energy.

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Violaxanthin Deepoxidase (VDE)

Violaxanthin deepoxidase enzyme.

VDE is an enzyme responsible for the conversion of violaxanthin to zeaxanthin in plants. This process helps regulate photosynthesis and protect plants from damage caused by excess light.

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Ascorbate

A water-soluble antioxidant involved in various metabolic processes.

Ascorbate, also known as vitamin C, is a powerful antioxidant found in plants. It plays a crucial role in protecting cells from damage caused by free radicals and helps with many important metabolic processes.

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Lipocalin

A type of protein domain that binds and transports small hydrophobic molecules.

Lipocalins are a large family of proteins found in various organisms. They share a common structural feature called a beta-barrel, which forms a pocket to bind and transport small hydrophobic molecules like lipids, steroids, and vitamins.