Problem 73 - Chemistry and Chemical Reactivity

Question

Voodoo lilies depend on carrion beetles for pollination. Carrion beetles are attracted to dead animals, and because dead and putrefying animals give off the horrible-smelling amine cadaverine, the lily likewise releases cadaverine (and the closely related compound putrescine, page 501 ). A biological catalyst, an enzyme, converts the naturally occurring amino acid lysine to cadaverine. (EQUATION CANNOT COPY) What group of atoms must be replaced in lysine to make cadaverine? (Lysine is essential to human nutrition but is not synthesized in the human body.)

Step-by-Step Solution

Answer

The carboxyl group \(-COOH\) in lysine must be replaced to form cadaverine.

Step 1: Understanding Lysine Structure

Lysine is a naturally occurring amino acid with the molecular formula \( C_6H_{14}N_2O_2 \). It contains an amino group \(-NH_2\), a carboxyl group \(-COOH\), and a side chain with a structure \( - (CH_2)_4 -NH_2 \). We need to identify what part of this structure is modified.

Step 2: Understanding Cadaverine Structure

Cadaverine is a biogenic amine with the molecular formula \( C_5H_{14}N_2 \). Its structure consists of a chain of five methylene groups \( (CH_2)_5 \) with an amino group at each end. Unlike lysine, there is no carboxyl group in cadaverine.

Step 3: Identifying the Conversion

The transformation of lysine to cadaverine involves removing the carboxyl group \(-COOH\) from lysine. The enzyme facilitates this reaction known as decarboxylation, which converts the amino acid into a biogenic amine.

Step 4: Conclude the Atom Group Replacement

To convert lysine into cadaverine, the carboxyl group \(-COOH\) of lysine must be replaced, leaving behind a straight chain of carbon atoms with amino groups attached at each end.

Key Concepts

Lysine

Lysine is an essential amino acid that plays a significant role in human nutrition. Despite its importance, the human body cannot synthesize lysine on its own, making it necessary to obtain it through dietary sources such as meats, beans, and dairy products.
This amino acid is characterized by its structure, which includes the molecular formula \( C_6H_{14}N_2O_2 \). It contains:

• An amino group \(-NH_2\)
• A carboxyl group \(-COOH\)
• A distinctive side chain of \(-(CH_2)_4 -NH_2\)

Understanding lysine's components is crucial for exploring its transformation into biogenic amines, such as cadaverine, in nature.

Enzyme Catalysis

Enzyme catalysis is the process by which enzymes accelerate chemical reactions. Enzymes are biological catalysts that facilitate transformations in living organisms.
They lower the activation energy required for a reaction, enhancing the reaction rate without being consumed in the process.

• Each enzyme is specific to particular substrates, which are the reactants in a reaction.
• They catalyze reactions by binding to substrates and forming an enzyme-substrate complex.
• The reaction takes place and products are released, leaving the enzyme ready to engage in another catalytic cycle.

In the case of lysine conversion, a specific enzyme catalyzes the decarboxylation reaction, transforming lysine into cadaverine.

Decarboxylation

Decarboxylation is a type of enzyme-catalyzed reaction, involving the removal of a carboxyl group \(-COOH\) from a molecule.
This process is vital in various biological reactions, aiding in the conversion of amino acids into other compounds.
When lysine undergoes decarboxylation, it transforms into cadaverine, a simpler amine compound.

• This process eliminates the carboxyl group from lysine.
• The resulting molecule (cadaverine) is left with a chain of methylene groups \((CH_2)_5\) with amino groups \(-NH_2\) at both ends.

This reaction illustrates the importance of enzyme-facilitated transformations in the natural production of biogenic amines.

Amino Acids

Amino acids are the building blocks of proteins, playing fundamental roles in various biological processes. Each has a basic structure consisting of an amino group \(-NH_2\), a carboxyl group \(-COOH\), and a side chain unique to each amino acid.
These side chains determine the unique behaviors and functions of amino acids in protein synthesis and other metabolic processes.

• They are classified based on their side chains' properties: non-polar, polar, acidic, and basic.
• They contribute to the structural framework of proteins and enzymes.
• Amino acids participate in intermediary metabolism as precursors to other biomolecules.

Understanding amino acids' structure and function assists in comprehending their transformation in enzymatic reactions, like the conversion of lysine into cadaverine.

Plant Pollination

Plant pollination is a critical process for the reproduction of flowering plants and often involves intricate interactions with animals or environmental agents.
In the case of voodoo lilies, carrion beetles play the central role in pollinating these plants.

• Carrion beetles are attracted by the smell of cadaverine, released by the lily to mimic decaying animals, which are the natural attractants for these beetles.
• By mimicking the scent of cadaverine, the lily ensures successful pollination as the beetles are lured to the flower, facilitating pollen transfer.

This fascinating example demonstrates the role of biogenic amines like cadaverine not only in biochemical conversions but also in ecological interactions.