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Endo‐Oligopeptidase A., a Putative Enkephalin‐Generating Enzyme, in the Vertebrate Retina
Author(s) -
Ferro E. S.,
Hamassaki D. E.,
Camargo A. C. M.,
Britto L. R. G.
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb06363.x
Subject(s) - colocalization , oligopeptidase , enkephalin , ganglion cell layer , chemistry , microbiology and biotechnology , biochemistry , antiserum , enzyme , biology , retinal , antibody , receptor , opioid , immunology
: Endo‐oligopeptidase A., EC 3.4.22.19, converts small enkephalin‐containing peptides into the corresponding enkephalins in vitro. We investigated the presence of endooligopeptidase A in the retina and its possible colocalization with enkephalins in retinal neurons. The specific activity of endo‐oligopeptidase A found in pigeon retinae (30.3 ± 7.3 mU/mg, mean ± standard deviation) was four times higher than in rabbit retinae (7.0 ± 1.1 mU/mg). The enzyme activity was not modified by EDTA, but it was enhanced by dithiothreitol and inhibited by zinc and 5.5′‐dithiobis(2‐nitrobenzoic acid). Immunohistochemical experiments with a purified antiserum against rabbit endo‐oligopeptidase A revealed labeled neurons in both the inner nuclear layer and the ganglion cell layer of pigeon and rabbit retinae. Double‐labeling immunofluorescence experiments demonstrated that about 90% of neurons containing endo‐oligopeptidase A‐like immune‐reactivity also contained [Leu 5 )‐enkephalin‐like immuno‐reactivity. These colocalization results may represent an important step toward the demonstration of the possible involvement of endo‐oligopeptidase A in enkephalin generation in vivo.