Identification of a calcium-dependent microsomal proteinase responsible for monobasic cleavage of chicken proalbumin

• Published in: Biochimica et biophysica acta Vol. 990; no. 3; pp. 276 - 279
• Main Authors: Peach, Robert J., Brennan, Stephen O.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 24.03.1989; Elsevier; North-Holland
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Calcium - physiology; Chicken; Chickens; Child; Endopeptidases - physiology; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Humans; Hydrogen-Ion Concentration; Hydrolases; Hydrolysis; KEX2 proteinase; Liver microsome; Microsomes, Liver - enzymology; Molecular Sequence Data; Prealbumin - isolation & purification; Prealbumin - metabolism; Proalbumin Christchurch; Proalbumin processing; Serum Albumin - isolation & purification; Yeast; α1-Antitrypsin Pittsburgh; Liver microsome; Proalbumin Christchurch; α 1-Antitrypsin Pittsburgh; Proalbumin processing; Yeast; PMSF; TLCK; Chicken; KEX2 proteinase; PCMB; Human; Enzyme; Cleavage site; Liver; Proteinase; Albumin; Microsome; Ripening; Autoradiography; Vertebrata; Electrophoretic mobility; Aves
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/S0304-4165(89)80045-5

The location and nature of the endoproteolytic activity involved in processing of proproteins has been studied in chicken liver microsomes. A membrane-bound, calcium-dependent proteinase was found to cleave chicken proalbumin with a monobasic cleavage site approx. 10-times faster than human proalbumin, which has a dibasic cleavage site. The mutant (human) proalbumin Christchurch (Arg(−1) → Gln), with a potential monobasic site, was not processed. The enzyme, which had a pH optimum of between 5.0 and 7.0, was not inhibited by serine or aspartyl proteinase inhibitors but was affected by some inhibitors of cysteine proteinases. The convertase was specifically inhibited by the reactive centre variant α 1-antitrypsin Pittsburgh, but not by normal α 1-antitrypsin.