Essential role of a family-32 carbohydrate-binding module in substrate recognition by Clostridium thermocellum mannanase CtMan5A.

The family-5 glycoside hydrolase domain (GH5) and the family-32 carbohydrate-binding module (CBM32) of Clostridium thermocellum mannanase CtMan5A, along with their genetically inactivated derivatives, were collectively or separately expressed. Their catalytic and substrate-binding abilities were measured to investigate importance of CBM32 in substrate recognition by CtMan5A. Characterization of the truncated derivatives of CtMan5A and isothermal calorimetry analysis of the interaction between the inactivated proteins and mannooligosaccharides suggested that GH5 and CBM32 collectively formed a substrate-binding site capable of accommodating a mannotetraose unit in CtMan5A.

Influence of a mannan binding family 32 carbohydrate binding module on the activity of the appended mannanase.

In general, cellulases and hemicellulases are modular enzymes in which the catalytic domain is appended to one or more noncatalytic carbohydrate binding modules (CBMs). CBMs, by concentrating the parental enzyme at their target polysaccharide, increase the capacity of the catalytic module to bind the substrate, leading to a potentiation in catalysis. Clostridium thermocellum hypothetical protein Cthe_0821, defined here as C.

Acetylacetoin synthase as a marker enzyme for detecting the 2,3-butanediol cycle.

Acetylacetoin synthase (AACSase) and acetylacetoin reductase (AACRase) are representative enzymes of the 2,3-butanediol cycle. After examining their induction conditions in various bacteria, the former was induced by acetoin and the latter by glucose. All strains carrying AACSase also had AACRase, but the reverse was not true.