REACTION OF ENZYMES AND PROTEINS WITH MUSTARD GAS (BIS(beta-CHLOROETHYL)SULFIDE)

Area of Science:

• Biochemistry
• Chemical kinetics

Background:

• Mustard gas (H) is a chemical agent known to react with biological molecules.
• Understanding protein-H interactions is crucial for assessing its biological impact.

Purpose of the Study:

• To determine the reaction rates of mustard gas (H) with various proteins.
• To elucidate the reaction kinetics and identify the specific protein residues involved.

Main Methods:

• Kinetic analysis of the reaction between mustard gas (H) and thirteen different proteins.
• pH-dependent studies to identify reactive functional groups (carboxyl and amino).
• Spectrophotometric analysis using Folin's phenol reagent to quantify reaction extent.

Main Results:

• Reaction rates varied by up to 100-fold across different proteins.
• Carboxyl groups were consistently reactive with H at pH 6.0, with bound H approximately equaling covered carboxyl groups.
• Amino groups showed minimal reactivity, except in yeast hexokinase.
• Folin's phenol reagent color intensity decreased with H treatment, indicating reaction, and was partially restored upon alkaline hydrolysis.

Conclusions:

• Protein structure influences mustard gas (H) reaction rates.
• Carboxyl groups are the main targets for H alkylation under the tested conditions.
• The reaction mechanism is bimolecular and can be reversed via hydrolysis.