Brain endo-oligopeptidase B: inactivation of LH-RH by hydrolysis of the Pro9-Gly-NH2(10) peptide bond

Abstract

1. The site of hydrolysis of rabbit brain endo-oligopeptidase B acting on luteinizing hormone-releasing hormone (LH-RH) was determined by isolating the products by chromatography on Aminex A-5 resin developed with pyridine-acetic acid buffer. The products [des-Gly-NH2(10)]-LH-RH, glycinamide and unhydrolyzed LH-RH were identified and shown to be homogeneous by amino acid analysis and high-voltage paper electrophoresis at pH 2.1 and 3.5 and recovered in yields of 58, 65 and 23%, respectively. 2. A sensitive analytical method for the measurement of 4-40 nmoles of glycinamide with an automatic amino acid analyzer was described. Aminex A-5 resin (0.90 x 15 cm) was eluted with sodium citrate buffer, pH 3.25 (0.2 N Na+) at 32 degrees C and ninhydrin was used for detection. 3. The data show that endo-oligopeptidase B acts as a post-proline cleaving enzyme that inactivates LH-RH by hydrolysis of the Pro9-Gly-NH2(10) peptide bond. The enzyme may participate in the metabolism of LH-RH in the central nervous system.