Protease activities in normal and schizophrenic human prefrontal cortex and white matter

Area of Science:

• Neuroscience
• Biochemistry
• Proteomics

Background:

• Protein and peptide degradation are crucial for brain function.
• Understanding enzyme activity in different brain regions is key to comprehending neurological processes.

Purpose of the Study:

• To quantify and compare endo- and exopeptidase activities in human prefrontal cortex (gray matter) and subjacent white matter.
• To investigate the relative contributions of these enzymes to protein and peptide degradation in distinct brain tissues.
• To explore potential differences in enzyme activity related to cellular composition and in chronic schizophrenia.

Main Methods:

• Post-mortem human prefrontal cortex and white matter tissues were analyzed.
• Activities of Cathepsin D and three dipeptidases (leucyl-glycine, glycyl-L-leucine, glycyl-glycine) were measured in frozen sections.
• Enzyme activities were correlated with histological composition, dry weight, total protein, DNA, and RNA concentrations.

Main Results:

• Cathepsin D activity and RNA concentration were significantly higher in cortical gray matter compared to white matter.
• Dipeptidase activities were generally higher in white matter than in gray matter.
• The order of dipeptidase activity was consistent across both tissues: glycyl-leucine > glycyl-glycine > leucyl-glycine.
• No significant differences in the activity of the four enzymes were observed in the cortex of patients with chronic schizophrenia.

Conclusions:

• The findings suggest preferential localization of Cathepsin D in cortical neurons and dipeptidases in neuroglia.
• These enzyme distribution patterns reflect distinct roles in protein and peptide metabolism within different brain compartments.
• The study provides baseline data on enzyme activities in healthy human brain tissue, with implications for understanding neurological disorders.