Acid proteinase of hypothalamus

Abstract

In a continuing study of the physiological role of protein breakdown in the hypothalamus, acid proteinase from bovine hypothalamus was purified about 1000-fold. The molecular weight of the enzyme was approximately 50,000. Masimal activity against hemoglobin was obtained at pH 3.2-3.5; serum albumin was split much more slowly. Hypothalamus acid proteinase was partially inhibited by beta-phenyl pyruvate, or benzethonium Cl, and was completely inhibited by low concentrations of pepstatin. This proteinase splits somatostatin, substance P, and analogs of substance P. The probable sites of enzyme action on these peptides were determined by the end group dansyl technique. The enzyme, most likely cathepsin D, may play an important role in the formation and breakdown of peptide hormones in the hypothalamus.

Purification and Characterisation of a Membrane‐Bound Substance‐P‐Degrading Enzyme from Human Brain

“…Although the substance-P-degrading enzyme purified from human brain is a neutral endopeptidase with a molecular weight very similar to that reported for a soluble neutral endopeptidase ( M , = 40 000) purified from bovine hypothalamus [20], the particulate human brain enzyme is clearly distinguishable from the cytosolic bovine enzyme. The soluble enzyme can be classified as a thiol enzyme as it is strongly inhibited by p-chloromercuribenzoate and iodoacetate while its action is potentiated by dithiothreitol.…”

“…A cytosolic enzyme has been partially purified from rat brain and shown to release phenylalanine and leucine preferentially from substance P, suggesting cleavage at two or more internal peptide bonds (Gln6-Phe7 or Phe7-Phe' and Glyg-Leu") [19]. Akopyan and coworkers [20] purified a neutral endopeptidase from bovine hypothalamus which degraded luteinizing-hormone-releasing hormone (luliberin) and somatostatin and also cleaved substance P, probably between Gln6-Phe' and Phe7-Phe'. In addition, a prolyl endopeptidase has been purified from rabbit brain and shown to cleave substance P between Abbreviations.…”

Purification of rabbit brain endooligopeptidases and preparation of antienzyme antibodies

“…Recently several laboratories have published descriptions of purified brain peptidases that hydrolyze oligopeptides such as bradykinin (Orlowski et al, 1979), angiotensin II (Knisatscheck & Bauer, 1979; Orlowski et al, 1979;Taylor & Dixon, 1980), substance P (Blumberg et al, 1980;Akopyan et al, 1978), LH-RH (Kock et al, 1974;Knisatscheck & Bauer, 1979; Orlowski et al, 1979;Hersch & McKelvy, 1979;Akopyan et al, 1978;Kuhl et al, 1979;Horsthemke & Bauer, 1980;Taylor & Dixon, 1980), and TRH (Rupnow et al, 1979). However, comparison of the properties of these enzymes with those of endooligopeptidases A and B indicates several similarities.…”

Capillary electrophoretic determination of cathepsin D activity using Oregon Green-labeled hemoglobin

“…In muscle it represents a major enzyme in the lysosomal pathway for degradation of myofibrillar proteins including myosin and titin [2]. Cathepsin D may be involved in the downregulation of hormones as it has been shown to catabolize peptides including bovine parathyroid hormone [3], substance P [4], somatostatin [5,6], and prolactin [6]. Cathepsin D has been found in high levels in senile plaque of brains from Alzheimer©s patients where it has been suggested to be responsible for proteolytic processing of a b-amyloid precursor [7±9].…”