Enkephalin convertase in the rat spinal cord.

3H-Guanidinoethylmercaptosuccinic acid (3H-GEMSA) a very selective inhibitor of enkephalin convertase, binds to the crude rat spinal cord homogenates saturably, reversibly and with high affinity. Scatchard analysis revealed two classes of binding sites with KD: 4.5 nM and 215 nM. A plot of dissociation experiment was nonlinear with the T1/2: 2 min and 6 min, respectively. 3H-GEMSA binding sites are evenly distributed throughout the rat spinal cord and their high density might suggest a physiological significance of enkephalin convertase in that tissue.