Disappearance of energy-transfer as a tool for fluorimetric study of the degradation of enkephalins by aminopeptidase activity from mouse brain.

The breakdown of the Tyr-Gly bond of enkephalins by aminopeptidases from mouse striatum can be studied by following the disappearance of energy transfer between the tyrosine residue and the dimethylaminonaphtalene sulfonyl group (DNS) in the biologicaly active fluorescent enkephalin, Tyr-Gly-Gly-Phe-Met-NH-(CH₂)₂-NH-DNS (Met-E-C₂-DNS). Such a process can be followed in a continuous mode yielding a simple method for the study of the effects of pH, temperature, etc… Furthermore, the enzymatic degradation of unsubstituted Met-E leads to several products, whereas Met-E-C₂-DNS gives only Gly-Gly-Phe-Met-NH-(CH₂)₂-DNS as the degradation product and behaves thus as a selective substrate in the study of aminopeptidases. This fluorimetric method should prove useful for studying the degradation of other neuropeptides or hormones containing one tyrosine or tryptophane residue in their sequence.