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Methionine enkephalin is hydrolyzed by aminopeptidase N on CD4+ and CD8+ spleen T cells
B C Miller1, D L Thiele, L B Hersh
1Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas 75235-9038.
Abstract:
Exogenous methionine enkephalin incubated with CD4+ or CD8+ T cells purified from murine spleen is metabolized primarily, if not exclusively, by aminopeptidase N (aminopeptidase M, EC 3.4.11.2), a membrane-anchored ectopeptidase. The enzyme activity is identified by its substrate specificity, sensitivity to inhibition by amastatin, and immunoreactivity with antibody to rat kidney aminopeptidase N. Activation of CD4+ T cells results in a small increase per cell in aminopeptidase N activity.
Insights
Aminopeptidase N primarily metabolizes methionine enkephalin in T cells. This enzyme
Area of Science:
- Immunology
- Enzymology
- Cell Biology
Background:
- Methionine enkephalin is a peptide with biological activity.
- T cells play crucial roles in immune responses.
- Enzymatic metabolism of neuropeptides by immune cells is not fully understood.
Purpose of the Study:
- To identify the primary enzyme responsible for metabolizing methionine enkephalin in T cells.
- To investigate the characteristics of this enzymatic activity.
- To determine if T cell activation affects this enzyme's activity.
Main Methods:
- Purification of CD4+ and CD8+ T cells from murine spleen.
- Incubation of T cells with exogenous methionine enkephalin.
- Enzyme activity assays using substrate specificity, amastatin inhibition, and antibody-based detection.
Main Results:
- Aminopeptidase N (APN) was identified as the main enzyme metabolizing methionine enkephalin in both CD4+ and CD8+ T cells.
- APN activity was confirmed by its substrate specificity, amastatin sensitivity, and immunoreactivity.
- CD4+ T cell activation led to a modest increase in APN activity per cell.
Conclusions:
- Aminopeptidase N is the key enzyme for methionine enkephalin metabolism in murine T cells.
- APN activity in T cells exhibits characteristic properties of this ectopeptidase.
- T cell activation can modulate APN expression or activity.