title: Alginate, the slime exopolysaccharide of Pseudomonas aeruginosa, binds human leukocyte elastase, retards inhibition by alpha 1-proteinase inhibitor, and accelerates inhibition by secretory leukoprotease inhibitor.
abstract: The interaction of alginate from Pseudomonas aeruginosa ATCC 39324 with human leukocyte elastase was studied by determining the effects of the polysaccharide on the amidolytic activity of the enzyme toward a range of synthetic peptide substrates of different length. The data support a model in which each elastase molecule interacts with a total of 19 uronic acid units on the alginate, primarily through electrostatic forces. Binding of alginate results in occlusion of distal subsites, most likely S4 and S5, of the enzyme's extended substrate-binding domain. As a result, alginate alone appears to be a weak inhibitor of the hydrolysis of long synthetic peptide substrates and [14C]elastin by elastase. Alginate also has effects on the antielastase function of naturally occurring protease inhibitors in the lung: It reduces the association rate of elastase and alpha 1-proteinase inhibitor, whereas it increases the association rate of elastase and secretory leukoprotease inhibitor. In the presence of 36 micrograms/ml alginate, the median concentration found in sputum from cystic fibrosis patients infected with mucoid strains of P. aeruginosa, the second-order rate constant for inhibition of elastase by secretory leukoprotease inhibitor is 2.6-fold greater than that for alpha 1-proteinase inhibitor. Alginate has only a minor effect on the antielastase activities of elafin and a recombinant form of the isolated C-terminal domain of secretory leukoprotease inhibitor. Based on these findings, alginate may be an important factor in determining the local distribution of leukocyte elastase and perturbing the overall protease-antiprotease balance in the infected lungs of cystic fibrosis patients.
authors.affiliation: Department of Pathology, State University of New York at Stony Brook 11794, USA.
authors.forename: Q L
authors.initials: QL
authors.lastname: Ying
authors.forename: M
authors.initials: M
authors.lastname: Kemme
authors.forename: S R
authors.initials: SR
authors.lastname: Simon
mesh_terms: D000464:Alginates / Q000378:metabolism* / Q000494:pharmacology; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism; D001672:Biocompatible Materials / Q000378:metabolism*; D004347:Drug Interactions; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D006801:Humans; D019272:Leukocyte Elastase; D008433:Mathematics; D008969:Molecular Sequence Data; D010196:Pancreatic Elastase / Q000378:metabolism* / Q000494:pharmacology; D011134:Polysaccharides / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary; D053491:Proteinase Inhibitory Proteins, Secretory; D011506:Proteins / Q000737:chemistry / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000737:chemistry*; D015842:Serine Proteinase Inhibitors / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D013379:Substrate Specificity; D000515:alpha 1-Antitrypsin / Q000378:metabolism
chemical_list: D000464:Alginates; D001426:Bacterial Proteins; D001672:Biocompatible Materials; D006603:Hexuronic Acids; D011134:Polysaccharides; D053491:Proteinase Inhibitory Proteins, Secretory; D011506:Proteins; D015842:Serine Proteinase Inhibitors; D000515:alpha 1-Antitrypsin; D012965:Sodium Chloride; D020723:Glucuronic Acid; D010196:Pancreatic Elastase; D019272:Leukocyte Elastase