Cyclic AMP regulates the biosynthesis of cellobiohydrolase in Cellulomonas flavigena growing in sugar cane bagasse
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ORIGINAL PAPER
Cyclic AMP regulates the biosynthesis of cellobiohydrolase in Cellulomonas Xavigena growing in sugar cane bagasse Jesús Antonio Herrera-Herrera · Odilia Pérez-Avalos · Luis M. Salgado · Teresa Ponce-Noyola
Received: 1 April 2009 / Revised: 6 August 2009 / Accepted: 10 August 2009 / Published online: 23 August 2009 © Springer-Verlag 2009
Abstract Cellulomonas Xavigena produces a battery of cellulase components that act concertedly to degrade cellulose. The addition of cAMP to repressed C. Xavigena cultures released catabolic repression, while addition of cAMP to induced C. Xavigena cultures led to a cellobiohydrolase hyperproduction. Exogenous cAMP showed positive regulation on cellobiohydrolase production in C. Xavigena grown on sugar cane bagasse. A C. Xavigena cellobiohydrolase gene was cloned (named celA), which coded for a 71- kDa enzyme. Upstream, a repressor celR1, identiWed as a 38 kDa protein, was monitored by use of polyclonal antibodies. Keywords Cellobiohydrolase · Cellulomonas Xavigena · cAMP regulation
Introduction Plant cellulose is the most abundant polysaccharide on Earth. Large varieties of cellulolytic fungi and bacteria produce enzymes known as cellulases, which convert insoluble cellulosic substrates to soluble sugars. The
Communicated by Jorge Membrillo-Hernández. J. A. Herrera-Herrera · O. Pérez-Avalos · T. Ponce-Noyola (&) Department of Biotechnology and Bioengineering CINVESTAV-IPN, Av. IPN 2508, 07300 Sn. Pedro Zacatenco, México, DF, Mexico e-mail: [email protected] L. M. Salgado Department of Biochemistry CICATA-IPN, Unidad Querétaro, Cerro Blanco 141, 076090 Colinas del Cimatario, Querétaro, Mexico
microbial conversion of cellulose requires a multiple enzyme system, which includes these three enzyme types: endoglucanases (1,4--D-glucan glucanohydrolase; EC 3.2.1.4), cellobiohydrolases (1,4--D-glucan cellobiohydrolase; EC 3.2.1.91) and -glucosidase (-D-glucoside glucohydrolases, EC 3.2.1.21) (Bayer et al. 1998). These enzymes are industrially important, and, consequently, substantial eVorts have been dedicated to study the genetics, structure, function and interaction of components of the cellulase enzyme systems (Shulein 2000). Most of the studied microorganisms synthesize cellulolytic enzyme complexes in relation to their growth conditions, but they apparently do not coordinate their activities by the same mechanisms. Bacteria of the genera Ruminococcus, Clostridium, Bacteroides and Acetivibrio, all anaerobic, have a specialized modularly arranged extracellular multienzyme complex, the cellulosome, which ensures maximal coordination and substrate accessibility (Schwarz 2001). In contrast, aerobic bacteria and fungi synthesize individual extracellular enzymes with speciWc modules that bind to their substrates. Despite the lack of detailed knowledge about the molecular mechanisms used to regulate the biosynthesis of these enzymes, in most analyzed bacteria the expression of the corresponding genes probably follows an induction mechanism regulated according to the c
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