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C–C Bond Formation: Aldol Condensation Overview

C–C Bond Formation: Aldol Condensation Overview

Aldol condensation is an important route in synthetic organic chemistry used to generate a new carbon–carbon bond under basic or acidic conditions. The aldol condensation reaction presented in Figure 1 constitutes an aldol addition reaction followed by the dehydration process.

C–C Bond Cleavage: Retro-Aldol Reaction

C–C Bond Cleavage: Retro-Aldol Reaction

The reverse of the aldol addition reaction is called the retro-aldol reaction. Here, the carbon–carbon bond in the aldol product is cleaved under acidic or basic conditions to form two molecules of carbonyl compounds. The mechanism of the reaction consists of three steps.
In the first step, as depicted in Figure 1, the base deprotonates the β-hydroxy ketone at the hydroxyl group to form an alkoxide ion.

Base-Catalyzed Aldol Addition Reaction

Base-Catalyzed Aldol Addition Reaction

As depicted in Figure 1, base-catalyzed aldol addition involves adding two carbonyl compounds in aqueous sodium hydroxide to form a β-hydroxy carbonyl compound.

Crossed Aldol Reaction Using Weak Bases

Crossed Aldol Reaction Using Weak Bases

This lesson deals with the crossed aldol reaction using weak bases. The self-condensation of an aldehyde having α hydrogen is prevented by adding it slowly to a mixture of formaldehyde and weak bases like hydroxide and alkoxide. Upon slow addition of the aldehyde, the base deprotonates the α carbon of the aldehyde to form the corresponding enolate. The enolate subsequently attacks the formaldehyde to form a single crossed product. Figure 1 depicts the aforementioned reaction.

Allosteric Proteins-ATCase

Allosteric Proteins-ATCase

Binding sites linkages can regulate a protein's function. For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis...

Dehydration of Aldols to Enals: Base-Catalyzed Aldol Condensation

Dehydration of Aldols to Enals: Base-Catalyzed Aldol Condensation

This lesson delves into the aldol condensation catalyzed by bases, where aldols undergo dehydration to enals. As shown in Figure 1, the β-hydroxy aldehyde formed in a base-catalyzed aldol addition reaction dehydrates on heating to yield an unsaturated carbonyl product, which is commonly referred to as an enal.

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Related Experiment Video

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Structural Biology and Analytical Chemistry Approaches for Characterizing C-Glycoside Metabolic Enzymes in Human Gut Microbiota

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B-factor Analysis and Conformational Rearrangement of Aldose Reductase.

Ganesaratnam K Balendiran¹, J Rajendran Pandian², Evin Drake¹

¹Department of Chemistry, WBSH 6017, Youngstown State University, One University Plaza, Youngstown, OH 44555.

Current Proteomics

|November 4, 2014

Summary

This summary is machine-generated.

Aldose Reductase (AR) catalyzes glucose reduction via an ordered mechanism. NADPH binding triggers a loop movement, crucial for product release and the rate-limiting step in catalysis.

Keywords:

Aldo-keto reductase B-factor TLS clustering crystal structure statistical analysis structural dynamics

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Area of Science:

Biochemistry
Enzymology
Structural Biology

Background:

Aldose Reductase (AR) is an enzyme catalyzing NADPH-dependent glucose reduction.
AR follows a sequential ordered kinetic mechanism where NADPH binds before the substrate.
Understanding AR's catalytic mechanism is vital for metabolic research.

Purpose of the Study:

To elucidate the kinetic and structural basis of Aldose Reductase's catalytic mechanism.
To investigate the role of a specific surface loop (residues 213-224) in AR function.
To identify the rate-limiting step in the AR-catalyzed reaction.

Main Methods:

Kinetic and structural experiments were employed.
Translation/Libration/Screw (TLS) analysis of apo AR crystal structures.
Analysis of B-factors in AR binary and ternary complexes.

Main Results:

A conformational change involving a hinge-like loop movement (residues 213-224) was observed upon NADPH binding.
This loop reorientation is proposed to facilitate NADP+ release, representing the rate-limiting step.
TLS analysis suggests the 213-224 loop moves as a rigid unit, further supported by B-factor analysis.

Conclusions:

The study reveals a crucial loop movement in Aldose Reductase's catalytic cycle.
This conformational change, driven by NADPH binding, is essential for product release and enzyme turnover.
The findings provide detailed insights into the mechanism of AR-catalyzed reactions.