title: Complex Formation of Human Proelastases with Procarboxypeptidases A1 and A2.
abstract: The pancreas secretes digestive proenzymes typically in their monomeric form. A notable exception is the ternary complex formed by proproteinase E, chymotrypsinogen C, and procarboxypeptidase A (proCPA) in cattle and other ruminants. In the human and pig pancreas binary complexes of proCPA with proelastases were found. To characterize complex formation among human pancreatic protease zymogens in a systematic manner, we performed binding experiments using recombinant proelastases CELA2A, CELA3A, and CELA3B; chymotrypsinogens CTRB1, CTRB2, CTRC, and CTRL1; and procarboxypeptidases CPA1, CPA2, and CPB1. We found that proCELA3B bound not only to proCPA1 (KD 43 nm) but even more tightly to proCPA2 (KD 18 nm), whereas proCELA2A bound weakly to proCPA1 only (KD 152 nm). Surprisingly, proCELA3A, which shares 92% identity with proCELA3B, did not form stable complexes due to the evolutionary replacement of Ala(241) with Gly. The polymorphic nature of position 241 in both CELA3A (∼4% Ala(241) alleles) and CELA3B (∼2% Gly(241) alleles) points to individual variations in complex formation. The functional effect of complex formation was delayed procarboxypeptidase activation due to increased affinity of the inhibitory activation peptide, whereas proelastase activation was unchanged. We conclude that complex formation among human pancreatic protease zymogens is limited to a subset of proelastases and procarboxypeptidases. Complex formation stabilizes the inhibitory activation peptide of procarboxypeptidases and thereby increases zymogen stability and controls activation.
authors.affiliation: From the Department of Molecular and Cell Biology and.
authors.forename: András
authors.initials: A
authors.lastname: Szabó
authors.affiliation: From the Department of Molecular and Cell Biology and the Paediatric Nutritional Medicine, Klinikum rechts der Isar (MRI), Else Kröner-Fresenius-Zentrum für Ernährungsmedizin (EKFZ), Technische Universität München (TUM), 85354 Freising, Germany, and.
authors.forename: Claudia
authors.initials: C
authors.lastname: Pilsak
authors.affiliation: From the Department of Molecular and Cell Biology and.
authors.forename: Melinda
authors.initials: M
authors.lastname: Bence
authors.affiliation: the Paediatric Nutritional Medicine, Klinikum rechts der Isar (MRI), Else Kröner-Fresenius-Zentrum für Ernährungsmedizin (EKFZ), Technische Universität München (TUM), 85354 Freising, Germany, and the ZIEL-Institute for Food and Health, 85354 Freising, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Witt
authors.affiliation: From the Department of Molecular and Cell Biology and Center for Exocrine Disorders, Boston University Henry M. Goldman School of Dental Medicine, Boston, Massachusetts 02118, miklos@bu.edu.
authors.forename: Miklós
authors.identifier: 0000-0003-4513-9922
authors.initials: M
authors.lastname: Sahin-Tóth
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D043424:Carboxypeptidase B / Q000235:genetics / Q000378:metabolism; D043422:Carboxypeptidases A / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D004789:Enzyme Activation / Q000502:physiology; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020125:Mutation, Missense; D010196:Pancreatic Elastase / Q000235:genetics / Q000378:metabolism*; D013552:Swine
chemical_list: C058173:CPB1 protein, human; D004792:Enzyme Precursors; D043422:Carboxypeptidases A; D043424:Carboxypeptidase B; D010196:Pancreatic Elastase
keywords: complex; elastase; metalloprotease; pancreas; pancreatitis; proteolytic enzyme; serine protease; zymogen activation