Screening for neuropeptide-metabolizing peptidases during the differentiation of chick embryo retina

Chick retina was screened for neuropeptide-metabolizing peptidase activity during development using a kininase bioassay in which hydrolysis of any peptide bond of bradykinin (Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9) leads to inactivation, combined with chromatographic bradykinin-product analysis. Bradykinin was degraded at a high rate, 6.1-26.6 mU/mg protein, by retina homogenates of all developmental stages. Kininase activity increased 2.3-fold from the 8th to the 18th embryonic day and 2-fold in the immediate posthatching period relative to the activity level at hatching. Bradykinin-product analysis, 57-113% recovery of the peptide fragments, indicated that kininase activity corresponded mostly to endopeptidase A- and to endopeptidase B-like activities (hydrolysis of Phe5-Ser6 and Pro7-Phe8 peptide bonds, respectively) and to angiotensin I-converting enzyme activity at all developmental stages. The data indicated that the relative amounts of these activities vary during retina differentiation.