Studies on choline acetyltransferase isolated from human brain.

Area of Science:

• Biochemistry
• Neuroscience

Background:

• Choline acetyltransferase (ChAT) is crucial for acetylcholine synthesis in the central nervous system.
• Understanding ChAT's biochemical properties is vital for neurological research.

Purpose of the Study:

• To characterize the purified human striatal choline acetyltransferase.
• To determine its kinetic parameters, molecular weight, and response to various effectors.

Main Methods:

• Purification of ChAT from human striatal tissue.
• Enzyme kinetics assays using acetyl-coenzyme A and choline.
• Molecular weight determination via Sephadex G-100 gel filtration.
• Sedimentation analysis using sucrose-density gradients.
• Assessing the effects of salts, chelating agents, and metal ions on enzyme activity.

Main Results:

• The enzyme exhibited a Km of 8 μM for acetyl-coenzyme A and 250 μM for choline.
• The predominant component had a molecular weight of approximately 67,000 daltons.
• Activity was enhanced by salts (KCl, NaCl, (NH4)2SO4) and chelators (EDTA, EGTA).
• Cupric sulfate (0.1 mM) caused near-complete inhibition, which was reversible by increasing enzyme, dithiothreitol, or EDTA concentrations.

Conclusions:

• The study provides key biochemical and kinetic data for human striatal ChAT.
• These findings contribute to understanding ChAT function and regulation in the brain.
• The characterization offers insights into potential therapeutic targets for neurological disorders involving acetylcholine.