Influence of the mannan binding module of beta-mannanase CfMan26A in the hydrolysis of mannan

Abstract: Hemicellulose is next to cellulose the most abundant polysaccharide on earth and as such an important renewable resource. Mannans are the major hemicellulose in so:ftwodd and are found as storage polysaccharide in various plants. -mannanases are the main mannan degrading enzymes. In this work the -1,4-mannanase from the soilliving bacteria Cellulosamas Jimi was studied and special focus was put on the product profile. Mannans are frequently used in the food-, paper- and textile industries and the field of possible applications is large. Deeper knowledge in the mannan degrading enzymes and the products fmmed from hydrolysis is required in order to enter this field and to optimize cmTent utilization. -1,4-mannanase, CfMan26A, from C. Jimi is an endo acting enzyme consisting of five domains. The first one is a glycosidehydrolase family 26 catalytic domain and the third is a family 23 carbohydrate binding domain (CBM) which binds mannans. Two variants of the enzyme were expressed, one fullength form comprising all five domains and one truncated fmm with only the first two domains, e.i. excluding the CBM. The hydrolysis products of mannohexaose and galactamannan (guar gum) from the two enzymes were studied with HPACD-PAD. The products from guar gum hydrolysis were also analyzed by the use ofsize exclusion chromatography. The results showed a striking difference in product profile for mannohexaose hydrolysis and a probable difference in the profile from guar gum hydrolysis, indicating that the CBM affected the product pattem. The activity on galactomam1an (locust bean gum and guar gum) was not significantly different between the two variants. But the results showed that both enzymes where restricted by the galactase side groups. In addition the affinity of the fullength enzyme to soluble galactamannans was confnmed with affinity gel electrophoresis. To conclude, this study showed that a CBM can affect the hydrolysis products of a -1,4- mannanase without significantly affecting the rate ofhydrolysis. This is of special importance when considering applications for the hydrolysis products. These findings can also be a fmiher step in elucidating the action of the CBM.