{alpha}-D-Glucuronidases from the xylanolytic thermophiles Clostridium stercorarium and Thermoanaerobacterium saccharolyticum

• Published in: Microbiology (Society for General Microbiology) Vol. 141; no. 9; pp. 2033 - 2040
• Main Authors: Bronnenmeier, Karin, Meissner, Harald, Stocker, Susanne, Staudenbauer, Walter L
• Format: Journal Article
• Language: English
• Published: Soc General Microbiol 01.09.1995
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/13500872-141-9-2033

Lehrstuhl für Mikrobiologie, Technische Universität München, Arcisstraβe 16, D-80290 München, Germany ABSTRACT -D-Glucuronidases were purified from the xylanolytic thermophiles Clostridium stercorarium and Thermoanaerobacterium saccharolyticum . This enzyme activity was found to be intracellular in each organism, with T. saccharolyticum producing much greater total activity. The specific activities of the purified enzymes (10 U mg -1 T. saccharolyticum ; 1.7 U mg -1 C. stercorarium ) differed by a factor of approximately 5. For the determination of enzyme activities, 4- O -methyl- -D-glucuronosyl-xylotriose was used as a substrate and the glucuronic acid released by -D-glucuronidase action was quantified by a colorimetric procedure. 4- O -Methyl- -D-glucuronosyl-xylotriose was the hydrolysis product that accumulated after exhaustive degradation of 4- O -methyl- -D-glucuronoxylan with xylanases of C. stercorarium . Hydrolysis of side chains in high-molecular-mass glucuronoxylan could not be detected. Neither of the enzymes was able to hydrolyse the chromogenic aryl-substrate p -nitrophenyl- -D-glucuronoside. Both -D-glucuronidases have a dimeric structure, with monomeric molecular masses of 72 and 76 kDa for C. stercorarium and of 71 kDa for T. saccharolyticum . The pl was estimated to be 4.3 for each enzyme. While both enzymes exhibited a similar pH optimum (pH 5.5-6.5) they differed in their thermostabilities. At 60 °C, half-lives of 14 and 2.5 h, respectively, were determined for the -D-glucuronidases of C. stercorarium and T. saccharolyticum . This description of -D-glucuronidase activity in thermophilic anaerobic bacteria extends our knowledge of these enzymes, previously purified and characterized only in fungi. Tel: +49 89 2105 2637. Fax: +49 89 2105 2360. Keywords: -D-glucuronidases, Clostridium, Thermoanaerobacterium , thermoactive enzymes, xylan