title: Purification and partial characterization of a calcium-stimulated protease from the cyanobacterium, Anabaena variabilis.
abstract: A calcium-stimulated protease was purified to apparent homogeneity from the heterocyst-forming cyanobacterium Anabaena variabilis ATCC 29413. As judged from experiments with inhibitors and chromogenic peptide substrates, the enzyme is a serine protease with a substrate specificity like trypsin. Its apparent relative molecular mass is 52,000. Calcium depletion inhibits the enzymic activity by 92%. Half-maximal activity requires about 0.5 microM free Ca2+. The enzyme binds to a hydrophobic column in a calcium-dependent manner, indicating calcium-induced exposure of a hydrophobic domain. The possible role of the protease in heterocyst differentiation is discussed.
mesh_terms: D002118:Calcium / Q000502:physiology*; D002845:Chromatography; D000458:Cyanobacteria / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D012697:Serine Endopeptidases / Q000302:isolation & purification*
chemical_list: D012697:Serine Endopeptidases; D002118:Calcium