Endo-oligopeptidase A, a putative enkephalin-generating enzyme, in the vertebrate retina.
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 immunoreactivity also contained [Leu5]-enkephalin-like immunoreactivity. These colocalization results may represent an important step toward the demonstration of the possible involvement of endo-oligopeptidase A in enkephalin generation in vivo.
Ferro
E S
ES
Department of Biophysics, São Paulo State University, Brazil.
Hamassaki
D E
DE
Camargo
A C
AC
Britto
L R
LR
D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000201:enzymology; D010856:Columbidae; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D004745:Enkephalins / Q000096:biosynthesis* / Q000235:genetics; D007150:Immunohistochemistry; D007700:Kinetics; D008666:Metalloendopeptidases; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational; D011817:Rabbits; D012160:Retina / Q000201:enzymology*; D012165:Retinal Ganglion Cells / Q000201:enzymology; D013379:Substrate Specificity
D004745:Enkephalins; D003546:Cysteine Endopeptidases; D008666:Metalloendopeptidases; C022510:thimet oligopeptidase