ABSTRACT
Brain cytosol is a rich source of peptide degrading enzymes. The resident oligopeptidases and exopeptidases likely participate in the terminal stages of intracellular protein degradation. There has been considerable interest in the role of these enzymes in neuropeptide metabolism, however their physiological significance in this process remains unclear. Although many publications describe protein and peptide hydrolases in crude or partially purified preparations, overlapping substrate specificities make it difficult to clearly define the enzymes involved. Brain cytosol contains a biologically unique macromolecule termed the multicatalytic endopeptidase complex. The first evidence that tissues contain a high molecular weight proteinase with multiple catalytic activities came from studies on the bovine pituitary enzyme. The action of Multicatalytic Endopeptidase Complex on neuropeptide substrates reflects the broad specificity seen with chromogenic substrates. Prolyl oligopeptidase was first detected in extracts of human uterine tissue as an oxytocin-degrading enzyme by R. Walter et al. in 1971.
