title: An extracellular--pepstatin insensitive acid protease produced by Thermoplasma volcanium.
abstract: In this study, some parameters for the production and caseinolytic activity of an extracellular thermostable acid protease from a thermoacidophilic archaeon Thermoplasma volcanium were determined. The highest level of growth and enzyme production were detected at pH 3.0 over an incubation period of 192 h at 60 degrees C. The pH optimum for the acid protease activity was 3.0 and the enzyme was fairly stable over a broad pH range (pH 3.0-8.0). The temperature for maximum activity of the enzyme was 55 degrees C and activity remained stable between 50 degrees C and 70 degrees C. These features could be of relevance for various biotechnological applications of this enzyme. Serine-(PMSF), cysteine-(DTT), metallo-(EDTA) and aspartate-(pepstatin) protease inhibitors did not inhibit the caseinolytic activity of the enzyme. Therefore, Tp. volcanium acid protease could be a member of the pepstatin-insensitive carboxyl proteinases.
authors.affiliation: Middle East Technical University, Department of Biological Sciences, 06531 Ankara, Turkey. biosemra@metu.edu.tr
authors.forename: Semra
authors.initials: S
authors.lastname: Kocabiyik
authors.forename: Hatice
authors.initials: H
authors.lastname: Ozel
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D002417:Cattle; D006863:Hydrogen-Ion Concentration; D008670:Metals; D008892:Milk / Q000737:chemistry / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D013696:Temperature; D013822:Thermoplasma / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D008670:Metals; D012697:Serine Endopeptidases; C104058:xanthomonapepsin