HIGH-MOLECULAR-WEIGHT ASPARTIC ENDOPEPTIDASE GENERATES A CORONARO-CONSTRICTORY PEPTIDE FROM THE BETA-CHAIN OF HEMOGLOBIN

Studying the influence of brain cathepsin D (EC 3.4.23.5) and high mol ecular weight (HMW) aspartic endopeptidase (EC 3.4.23.-) on the proces sing of hypothalamic calmodulin-binding coronaro-constrictory peptide factors from the beta chain of globin it was found that only HMW aspar tic endopeptidase generates the fragment 31-40 of the beta-chain of bo vine hembglobin (Hb) by cleavage of the Leu30-Leu31 and Phe40-Phe41 bo nds. Digestion of the beta-chain of globin was performed at 37-degrees -C at an enzyme/substrate ratio of 1:80 at pH 3.5 using different time s of incubation (from 4 h to 10 h). The resulting peptides were separa ted by reversed-phase high-performance liquid chromatography (HPLC) an d then identified by amino acid analysis and Edman degradation. The di fferences in specificity and activity of these two brain aspartic prot einases could be explained by their different structural features. Our finding provides evidence for a different biological function of thes e two enzymes. Data obtained give us reason to suppose that HMW aspart ic proteinase probably can participate in the processing of the corona ro-constrictory peptide in vivo by limited proteolysis of Hb or Hb-lik e protein.