Related Experiment Videos
How is kyotorphin (Tyr-Arg) generated in the brain?
Neuropeptides
|February 1, 1985
Summary
Kyotorphin (Tyr-Arg) is broken down by brain enzymes but accumulates when bestatin inhibits this degradation. This suggests kyotorphin is produced by specific enzymes near the degrading enzymes in brain tissue.
Area of Science:
- Neurochemistry
- Enzymology
Background:
- Kyotorphin (Tyr-Arg) is a dipeptide with potential biological activity.
- Its rapid degradation in brain tissue suggests localized enzymatic regulation.
Purpose of the Study:
- To investigate the enzymes involved in kyotorphin degradation and accumulation in brain tissue.
- To identify the cellular localization of kyotorphin metabolism.
Main Methods:
- Incubation of monkey brain homogenates and slices with kyotorphin.
- Assay of kyotorphin degradation and accumulation.
- Inhibition studies using bestatin, leupeptin, p-chloromercuribenzoate, phenylmethylsulfonylfluoride, and diisopropylphosphate.
- Fractionation of brain homogenates to determine subcellular localization.
Main Results:
- Kyotorphin was rapidly degraded by monkey brain homogenates and purified membrane-bound aminopeptidase.
- Bestatin significantly inhibited kyotorphin degradation, leading to time-dependent accumulation.
- Leupeptin and p-chloromercuribenzoate inhibited bestatin-induced kyotorphin accumulation.
- Accumulation was primarily observed in the crude mitochondrial (P2) and synaptosomal fractions.
Conclusions:
- Membrane-bound aminopeptidase rapidly degrades kyotorphin in the brain.
- Kyotorphin may be generated by leupeptin-sensitive "kyotorphin converting enzymes" located near the degrading aminopeptidase, particularly in synaptosomes.