Sandbox Reserved 1846: Difference between revisions
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== Function == | == Function == | ||
LCC catalyzes the hydrolysis of the ester bonds in PET polymers and breaks them down into their constituent monomers: terephthalic acid and ethylene glycol. The enzyme operates through a catalytic triad that consists of S165, D210, and H242. Using these residues, LCC can perform nucleophilic attacks on the carbonyl carbon atoms of the ester bonds in PET. During catalysis, the substrate binds in an elongated, predominantly hydrophobic groove present in the enzyme's structure. | LCC catalyzes the hydrolysis of the ester bonds in PET polymers <scene name='10/1075247/2he_met_3/1'>2-HE(MET)3</scene> and breaks them down into their constituent monomers: terephthalic acid and ethylene glycol. The enzyme operates through a catalytic triad that consists of S165, D210, and H242. Using these residues, LCC can perform nucleophilic attacks on the carbonyl carbon atoms of the ester bonds in PET. During catalysis, the substrate binds in an elongated, predominantly hydrophobic groove present in the enzyme's structure. | ||
LCC functions optimally at elevated temperatures (around 65-72°C), which approaches the [https://en.wikipedia.org/wiki/Glass_transition glass transition] temperature of PET. This temperature range maximizes PET chain mobility and makes the polymer more accessible to enzymatic action. The enzyme is remarkably thermostable compared to other PET hydrolases, with a melting temperature of 84.7°C. This property allows it to remain functional under these high-temperature conditions. Also unlike other PET hydrolases such as Is-PETase, BTA1, BTA2, and FsC, LCC has substantially higher catalytic efficiency. Specifically, LCC has an initial PET-specific depolymerization rate of 93.2 mg TAeq. h⁻¹ mg⁻¹ enzyme at 65°C with amorphous PET. This means that it us at least 33 times more efficient than other tested enzymes.<ref name="Tournier">PMID:32269349</ref> | LCC functions optimally at elevated temperatures (around 65-72°C), which approaches the [https://en.wikipedia.org/wiki/Glass_transition glass transition] temperature of PET. This temperature range maximizes PET chain mobility and makes the polymer more accessible to enzymatic action. The enzyme is remarkably thermostable compared to other PET hydrolases, with a melting temperature of 84.7°C. This property allows it to remain functional under these high-temperature conditions. Also unlike other PET hydrolases such as Is-PETase, BTA1, BTA2, and FsC, LCC has substantially higher catalytic efficiency. Specifically, LCC has an initial PET-specific depolymerization rate of 93.2 mg TAeq. h⁻¹ mg⁻¹ enzyme at 65°C with amorphous PET. This means that it us at least 33 times more efficient than other tested enzymes.<ref name="Tournier">PMID:32269349</ref> | ||
LCC's function is limited by PET [https://en.wikipedia.org/wiki/Crystallization_of_polymers crystallinity], as the enzyme can more effectively hydrolyze amorphous regions of the polymer. As PET crystallinity increases during the depolymerization reaction (due to exposure to elevated temperatures), the enzyme's efficiency decreases. This limits complete depolymerization unless optimal conditions and enzyme variants are used. | LCC's function is limited by PET [https://en.wikipedia.org/wiki/Crystallization_of_polymers crystallinity], as the enzyme can more effectively hydrolyze amorphous regions of the polymer. As PET crystallinity increases during the depolymerization reaction (due to exposure to elevated temperatures), the enzyme's efficiency decreases. This limits complete depolymerization unless optimal conditions and enzyme variants are used. | ||
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== Structural Overview == | == Structural Overview == | ||
<scene name='10/1075246/4eb0_helix_sheet/1'>Helix Sheet colored</scene> | |||
=== Catalytic Triad === | === Catalytic Triad === | ||
LCC catalyzes the breakdown of PET using a classic serine hydrolase mechanism involving a catalytic triad of Ser165, His242, and Asp210. The reaction begins when His242 deprotonates Ser165, which activates it as a nucleophile. Ser165 then attacks the carbonyl carbon of an ester bond in the PET polymer. This forms a tetrahedral intermediate. This intermediate is stabilized by an oxyanion hole. The oxyanion hole is formed by the backbone amides of Met166 and Tyr95. The intermediate collapses; one product is released and an acyl-enzyme intermediate is formed. A water molecule, activated by His242, then attacks the acyl-enzyme, releasing the second product and resetting the enzyme’s active site. | LCC catalyzes the breakdown of PET using a classic serine hydrolase mechanism involving a <scene name='10/1075246/Catalytic_triad3/1'>catalytic triad</scene> of Ser165, His242, and Asp210. The reaction begins when His242 deprotonates Ser165, which activates it as a nucleophile. Ser165 then attacks the carbonyl carbon of an ester bond in the PET polymer. This forms a tetrahedral intermediate. This intermediate is stabilized by an oxyanion hole. The oxyanion hole is formed by the backbone amides of Met166 and Tyr95. The intermediate collapses; one product is released and an acyl-enzyme intermediate is formed. A water molecule, activated by His242, then attacks the acyl-enzyme, releasing the second product and resetting the enzyme’s active site. | ||
[[Image:Mechanism_(1).jpeg|1100 px]] | [[Image:Mechanism_(1).jpeg|1100 px]] | ||
