Molecular Dynamics Simulations of Family 7 Cellobiohydrolase Mutants Aimed at Reducing Product Inhibition

Autor(es)

Silveira, Rodrigo L. ^[1] ; Skaf, Munir S. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Inst Chem, BR-13084862 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Physical Chemistry B; v. 119, n. 29, p. 9295-9303, JUL 23 2015.
• Citações Web of Science: 17

Resumo

Enzymatic conversion of lignocellulosic biomass into biofuels and chemicals constitutes a potential route for sustainable development. Cellobiohydrolases are key enzymes used in industrial cocktails for depolymerization of crystalline Cellulose, and their mechanism of action has been intensely studied in the past several years. Provided with a tunnel-like substrate-binding cavity, cellobiohydrolases possess the ability to processively hydrolyze glycosidic bonds of crystalline cellulose, yielding one molecule of cellobiose per catalytic cycle. As such, cellobiose expulsion from the product binding site is a necessary step in order to allow for the processive hydrolysis mechanism. However, the high-affinity binding of cellobiose to the enzyme impairs the process and causes activity inhibition due to reaction products. Here, we use molecular dynamics simulations to study the binding of cellobiose to the Trichoderma reesei Cel7A (TrCel7A) cellobiohydrolase and the effects of mutations that reduce cellobiose binding, without affecting the structural and dynamical integrities of the enzyme. We observe that the product binding site exhibits an intrinsic flexibility that can sterically hinder cellobiose release. Several point mutations in the product binding site reduce cellobiose-enzyme interactions, but not all modifications are able to maintain the structural integrity of the enzyme. In particular, imitation of charged residues in the TrCel7A product binding site causes perturbations that affect the structure of the loops that form the substrate-binding tunnel of the enzyme and, hence, may affect TrCel7A function in other steps of the hydrolysis mechanism. Our results suggest there is a trade-off between product inhibition and catalytic efficiency, and they provide directions for cellulases engineering. (AU)

• Processo FAPESP: 14/10448-1 - Aspectos moleculares da arquitetura de paredes celulares de plantas
• Beneficiário: Rodrigo Leandro Silveira
• Linha de fomento: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 13/08293-7 - CECC - Centro de Engenharia e Ciências Computacionais
• Beneficiário: Munir Salomao Skaf
• Linha de fomento: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs