Stepping through the Shikimate Pathway II
TLDRThe video script delves into the shikimate pathway, a crucial metabolic process for the biosynthesis of aromatic amino acids. It begins with the formation of enolpyruvate shikimate phosphate from three building blocks. The script then explains the transformation of this molecule into prephenate and subsequently into phenylalanine and tyrosine, two essential aromatic amino acids. The process involves an anti-elimination reaction catalyzed by chorismate synthase, resulting in the formation of chorismate, which undergoes isomerization to prephenate. This isomerization is facilitated by chorismate mutase, with a detailed mechanism to be covered in a future webcast. The script also describes the decarboxylation process, leading to the differentiation between phenylalanine and tyrosine. The final steps involve the introduction of an amino group through a transamination process, catalyzed by an amino transferase enzyme, to complete the synthesis of these vital amino acids.
Takeaways
- πΏ **Shikimate Pathway Overview**: The script discusses the transformation of enolpyruvate shikimate phosphate into prephenate and then into the aromatic amino acids phenylalanine and tyrosine through the shikimate pathway.
- π¬ **Molecular Transformation**: The process involves converting a highly functionalized molecule into a benzene ring, which is a key step in producing aromatic amino acids.
- β‘οΈ **Anti Elimination**: Chorismate synthase catalyzes an anti elimination reaction, resulting in the formation of cyclohexadiene, which is the molecule chorismate.
- π **Isomerization Reaction**: Chorismate mutase facilitates the isomerization of chorismate to prephenate, involving the repositioning of the enolpyruvate portion of the molecule.
- π **Electron Flow**: The isomerization is a concerted process with the flow of electrons, leading to the formation of a new carbon-carbon bond and the breaking of a carbon-oxygen bond.
- β³ **Decarboxylation Process**: The differentiation between phenylalanine and tyrosine is achieved through a decarboxylation step, which is catalyzed by prephenate dehydratase.
- π§ **Byproducts Formation**: The decarboxylation results in the production of CO2 and a hydroxide ion, with the structure becoming a precursor to phenylalanine.
- π **Reductive Amination**: An amino transferase is involved in a reductive amination process to introduce an amino group at the Ξ± position of phenylalanine.
- π« **Hydrogen Removal**: For the production of tyrosine, prephenate dehydrogenase removes a hydrogen atom (as a hydride) from the molecule, which is absorbed by the cofactor NAD+.
- π **Cofactor Role**: NAD+ acts as a hydride acceptor, converting to NADH, which is essential for the production of the tyrosine precursor.
- π¬ **Chemical Details**: The script hints at further exploration of the chemistry involved in the amino transferase enzyme's action in a future webcast.
Q & A
What is the final product of the shikimate pathway discussed in the webcast?
-The final products of the shikimate pathway discussed are the aromatic amino acids phenylalanine and tyrosine.
What is the first transformation that enolpyruvate shikimate phosphate undergoes?
-The first transformation is an anti elimination, which increases the degree of unsaturation and leads to the formation of chorismate.
Which enzyme catalyzes the conversion of chorismate to prephenate?
-The enzyme that catalyzes this conversion is called chorismate mutase.
What type of reaction is used to form the benzene ring from the highly functionalized molecule?
-An isomerization reaction is used to form the benzene ring from the highly functionalized molecule.
What is the role of prephenate dehydratase in the pathway?
-Prephenate dehydratase catalyzes the decarboxylation of prephenate, which is a key step in differentiating phenylalanine from tyrosine.
How is the hydroxyl group eliminated during the formation of phenylalanine?
-The hydroxyl group is eliminated through a decarboxylation reaction catalyzed by prephenate dehydratase, which also involves the elimination of a hydrogen atom.
What is the purpose of the amino transferase in the pathway?
-The amino transferase is used to introduce an amino group at the Ξ± position of phenylalanine through a transamination process.
What is the difference in the reaction that leads to the formation of tyrosine instead of phenylalanine?
-In the formation of tyrosine, the hydroxyl group must remain in place, and the hydrogen atom is removed through a reaction catalyzed by prephenate dehydrogenase, which involves the absorption of hydride by the cofactor NAD+.
How does the cofactor NAD+ participate in the reaction that produces the precursor to tyrosine?
-NAD+ acts as a hydride acceptor, forming NADH and allowing for the production of the precursor to tyrosine with a phenol group.
What is the final step in converting the precursor to tyrosine into the actual amino acid?
-The final step involves a reductive amination reaction, where the carbonyl group is transformed into the corresponding L-amino acid, yielding tyrosine.
What does the term 'unsaturation' refer to in the context of the shikimate pathway?
-In the context of the shikimate pathway, 'unsaturation' refers to the introduction of double bonds or rings into the molecule, which is necessary for the formation of the aromatic ring.
How does the process of introducing unsaturation contribute to the formation of the aromatic ring?
-Introducing unsaturation through the formation of a cyclohexadiene intermediate (chorismate) allows for the subsequent reactions that lead to the formation of the benzene ring found in the aromatic amino acids.
Outlines
πΏ Shikimate Pathway to Aromatic Amino Acids
This paragraph explains the biochemical transformation of enolpyruvate shikimate phosphate into prephenate and subsequently into the aromatic amino acids phenylalanine and tyrosine. The process involves increasing unsaturation by converting the functionalized molecule into a benzene ring. Initially, an anti elimination reaction catalyzed by chorismate synthase results in the formation of chorismate, which then undergoes isomerization to prephenate. This isomerization is facilitated by the enzyme chorismate mutase and is characterized by the breaking of a carbon-oxygen bond and the formation of a carbon-carbon bond through a concerted electron flow. The paragraph also discusses the subsequent steps of decarboxylation and amino transferase reactions that lead to the production of phenylalanine and tyrosine, including the role of the cofactor NAD+ in accepting a hydride to form NADH during the process.
π¬ Building the Aromatic Ring through Functional Group Manipulations
The second paragraph focuses on the progression from the initial carbocyclic ring to the formation of the aromatic ring through a series of functional group manipulations. It emphasizes the introduction of unsaturation as a key step in this transformation process. The paragraph succinctly summarizes the complex biochemical pathway described in the first paragraph, highlighting the significance of each step in the synthesis of the aromatic amino acids.
Mindmap
Keywords
π‘Shikimate pathway
π‘Enolpyruvate shikimate phosphate
π‘Unsaturation
π‘Chorismate synthase
π‘Cyclohexadiene
π‘Isomerization
π‘Chorismate mutase
π‘Decarboxylation
π‘Prephenate dehydratase
π‘Amino transferase
π‘NAD+ and NADH
Highlights
The shikimate pathway is discussed in detail, showing how three building blocks come together to produce enolpyruvate shikimate phosphate.
The molecule enolpyruvate shikimate phosphate is transformed into prephenate and then into the aromatic amino acids phenylalanine and tyrosine.
Greater degrees of unsaturation are introduced by transforming the highly functionalized molecule into a benzene ring through an anti elimination reaction.
Chorismate synthase catalyzes the 1,4 elimination to build in cyclohexadiene, forming the molecule chorismate.
Chorismate undergoes isomerization to give prephenate, involving a concerted flow of electrons and bond rearrangement.
Chorismate mutase is the enzyme responsible for the isomerization reaction.
The carbon-oxygen bond highlighted in yellow breaks, and a carbon-carbon bond forms during the isomerization.
Prephenate dehydratase catalyzes the decarboxylation that differentiates phenylalanine from tyrosine.
Decarboxylation eliminates the hydroxyl group, producing CO2 and hydroxide as byproducts.
The resulting structure is a precursor to phenylalanine, with a remaining hydrogen atom at the four position of the benzene ring.
An amino transferase introduces an amino group at the Ξ± position of phenylalanine through a reductive amination process.
For tyrosine, the hydroxyl group must be retained while the hydrogen atom is removed.
Prephenate dehydrogenase catalyzes the decarboxylation and elimination of hydride to produce the precursor to tyrosine.
NAD+ acts as a hydride acceptor, forming NADH and allowing the production of the phenol-containing aromatic ring.
The same amino transferase reaction is used to convert the carbonyl group to the corresponding L-amino acid, completing the synthesis of tyrosine.
The overall steps in synthesizing the aromatic amino acids involve a series of functional group manipulations and introducing unsaturation to form the aromatic ring.
The chemistry and mechanism of the amino transferase enzyme may be discussed in more detail in an upcoming webcast.
The cofactor roles and transamination process are briefly mentioned but not detailed in this webcast.
Transcripts
5.0 / 5 (0 votes)
Thanks for rating: