Human brain aldehyde dehydrogenase: activity with DOPAL and isozyme distribution

Area of Science:

• Biochemistry
• Neuroscience
• Enzymology

Background:

• Aldehyde dehydrogenase (ALDH) is identified as the primary enzyme responsible for metabolizing DOPAL in the human brain.
• Previous research highlights ALDH's critical role in neurotransmitter metabolism.

Purpose of the Study:

• To investigate the activity, distribution, and characteristics of aldehyde dehydrogenase (ALDH) in the human brain.
• To determine if chronic alcoholism affects ALDH activity or its properties.

Main Methods:

• Assessed ALDH activity in various brain regions (cerebellum, corpus striatum, pons) and subcellular fractions (mitochondrial, microsomal).
• Utilized isoelectric focusing (IEF) and kinetic analysis (Km values) to characterize ALDH isozymes.
• Compared ALDH activity and protein content in brain samples from alcoholics and a control group.

Main Results:

• Highest ALDH activity was observed in the cerebellum, corpus striatum, and pons, primarily in mitochondrial and microsomal fractions.
• Isoelectric focusing revealed two distinct ALDH activity bands, and kinetic studies indicated dual Km values, suggesting the presence of two isozymes.
• No significant differences in total ALDH activity, subcellular distribution, or protein content were found between alcoholics and the control group.
• ALDH activity remained unaffected by the presence of DOPAC, pargyline, pyrazole, or ethanol in the assay.

Conclusions:

• The human brain possesses at least two distinct ALDH isozymes, predominantly located in mitochondrial and microsomal fractions of specific brain regions.
• Chronic alcoholism does not appear to alter the overall activity, distribution, or protein levels of brain ALDH.
• ALDH activity in these brain regions is not significantly influenced by common ALDH inhibitors or ethanol itself under the tested conditions.