Structural basis of exo--mannanase activity in the GH2 family

Author(s):Show less -

Domingues, Mariane Noronha ; Moreira Souza, Flavio Henrique ; Vieira, Plinio Salmazo ; Bueno de Morais, Mariana Abrahao ^[1] ; Zanphorlin, Leticia Maria ^[1] ; dos Santos, Camila Ramos ^[1] ; Siqueira Pirolla, Renan Augusto ; Honorato, Rodrigo Vargas ^[2] ; Lopes de Oliveira, Paulo Sergio ^[2] ; Gozzo, Fabio Cesar ^[3] ; Murakami, Mario Tyago ^[1]

Affiliation

^[1] Brazilian Bioethanol Sci & Technol Lab, BR-13083970 Campinas, SP - Brazil

^[2] Brazilian Ctr Res Energy & Mat, Brazilian Biosci Natl Lab, BR-13083970 Campinas, SP - Brazil

^[3] Univ Estadual Campinas, Dalton Mass Spectrometry Lab, BR-13083970 Campinas, SP - Brazil

• Document type: Journal article
• Source: Journal of Biological Chemistry; v. 293, n. 35, p. 13636-13649, AUG 31 2018.
• Web of Science Citations: 2

Abstract

The classical microbial strategy for depolymerization of -mannan polysaccharides involves the synergistic action of at least two enzymes, endo-1,4--mannanases and -mannosidases. In this work, we describe the first exo--mannanase from the GH2 family, isolated from Xanthomonas axonopodis pv. citri (XacMan2A), which can efficiently hydrolyze both manno-oligosaccharides and -mannan into mannose. It represents a valuable process simplification in the microbial carbon uptake that could be of potential industrial interest. Biochemical assays revealed a progressive increase in the hydrolysis rates from mannobiose to mannohexaose, which distinguishes XacMan2A from the known GH2 -mannosidases. Crystallographic analysis indicates that the active-site topology of XacMan2A underwent profound structural changes at the positive-subsite region, by the removal of the physical barrier canonically observed in GH2 -mannosidases, generating a more open and accessible active site with additional productive positive subsites. Besides that, XacMan2A contains two residue substitutions in relation to typical GH2 -mannosidases, Gly(439) and Gly(556), which alter the active site volume and are essential to its mode of action. Interestingly, the only other mechanistically characterized mannose-releasing exo--mannanase so far is from the GH5 family, and its mode of action was attributed to the emergence of a blocking loop at the negative-subsite region of a cleft-like active site, whereas in XacMan2A, the same activity can be explained by the removal of steric barriers at the positive-subsite region in an originally pocket-like active site. Therefore, the GH2 exo--mannanase represents a distinct molecular route to this rare activity, expanding our knowledge about functional convergence mechanisms in carbohydrate-active enzymes. (AU)

• FAPESP's process: 16/06509-0 - Understanding the enzymatic system involved in the degradation and utilization of xyloglucans from the plant pathogen Xanthomonas axonopodis pv. citri
• Grantee: Plínio Salmazo Vieira
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 15/26982-0 - Exploring novel strategies for depolymerization of plant cell-wall polysaccharides: from structure, function and rational design of glycosyl hydrolases to biological implications and potential biotechnological applications
• Grantee: Mário Tyago Murakami
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 16/19995-0 - Analysis of structural and functional diversity of GH43 enzymes from Xanthomonas axonopodis pv. citri: biological implications and potential biotechnological applications
• Grantee: Mariana Abrahão Bueno de Morais
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 13/24622-0 - Elucidation of the mechanistic basis of family GH62 present in organisms specialized in the degradation of plant biomass
• Grantee: Flavio Henrique Moreira de Souza
• Support Opportunities: Scholarships in Brazil - Post-Doctoral