title: Cellulose hydrolysis by cellobiohydrolase Cel7A shows mixed hyperbolic product inhibition.
abstract: In order to establish which are the contribution of linear (total), hyperbolic (partial) or parabolic inhibitions by cellobiose, and also a special case of substrate inhibition, the kinetics of cellobiohydrolase Cel7A obtained from Trichoderma reesei was investigated. Values of kinetic parameters were estimated employing integrated forms of Michaelis-Menten equations through the use of non-linear regression, and criteria for selecting inhibition models are discussed. With cellobiose added at the beginning of the reaction, it was found that cellulose hydrolysis follows a kinetic model, which takes into account a mixed hyperbolic inhibition, by cellobiose with the following parameter values: K (m) 5.0 mM, K (ic) 0.029 mM, K (iu) 1.1 mM, k (cat) 3.6 h(-1) and k (cat') 0.2 h(-1). Cellulose hydrolysis without initial cellobiose added also follows the same inhibition model with similar values (4.7, 0.029 and 1.5 mM and 3.2 and 0.2 h(-1), respectively). According to Akaike information criterion, more complex models that take into account substrate and parabolic inhibitions do not increase the modulation performance of cellulose hydrolysis.
authors.affiliation: CITAB - Departamento de Biologia e Ambiente, Universidade de Trás-os-Montes e Alto Douro, Apartado 1013, 5001-801, Vila Real, Portugal. bezerra@utad.pt
authors.forename: Rui Manuel Furtado
authors.initials: RM
authors.lastname: Bezerra
authors.forename: Albino A
authors.initials: AA
authors.lastname: Dias
authors.forename: Irene
authors.initials: I
authors.lastname: Fraga
authors.forename: António Nazaré
authors.initials: AN
authors.lastname: Pereira
mesh_terms: D002480:Cellulase / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism*; D043366:Cellulose 1,4-beta-Cellobiosidase / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D013379:Substrate Specificity
chemical_list: D002482:Cellulose; D002480:Cellulase; D043366:Cellulose 1,4-beta-Cellobiosidase