Kinetics and stereochemistry of the Cellulomonas fimi β-mannanase studied using 1H-NMR

Endo–1,4-β-mannanases (β-mannanases) randomly hydrolyse the mannosidic bonds within the main chain of various mannans and heteromannans. Some of these polysaccharides are hemicelluloses, a major part of the plant cell-wall. The β-mannanases have been assigned to family 5 and 26 of the glycoside hydrolase clan A. This work presents a detailed kinetic analysis of the family 26 β-mannanase CfMan26A from the soil-bacterium Cellulomonas fimi. The full-length enzyme consists of five modules: a family 26 catalytic module, an immunoglobulin-like module, a mannan-binding module, a surface layer homology-module and a module of unknown function. A truncated variant consisting of the catalytic module and the immunoglobulin-like module was used in these studies. The degradation of mannotriose, mannotetraose and mannopentaose was studied by 1H-NMR. First, the mutarotation of one of the hydrolysis products (mannose) was determined to be 1.7 10−5s−1 at 5°C and pH 5.0. As expected for a family 26 glycoside hydrolase, the ...