Characterization of SdAmy, a novel alpha amylase from Saccharophagus degradans

Abstract

Saccharophagus degradans is a gram-negative marine bacterium. It is the most versatile bacterium in terms of the degradation of complex polymers (CP) found to date. The high rate of degradation of different polysaccharides that this bacterium has makes it a candidate to obtain and investigate the properties of the enzymes that degrade these polymers. The objective of this work is to carry out the structural characterization of SdAmy, a novel alphaamylase from S. degradans, and the study of the CBM20 domain of SdAmy. The enzyme is composed mainly by a N-terminal catalytic domain (CD), a central AamyC domain (AamyC) and a carbohydrate-binding module family 20 at the C-terminal (CBM20). SdAmy and the CBM20 domain was successfully expressed in Escherichia coli cells, purified and its properties were investigated. The enzyme showed maximum activity at 40°C and pH 5.0. SdAmy showed a Vmax and Km values of about -1.min-1 and 0,34 g.l-1 , respectively, when used potato starch as substrate. The activity and stability of SdAmy was improved in the presence of calcium. Carbohydrate binding assays showed that the CBM20 domain bind to amylose with a Kad of 3.13 ± 0.25 ml/g. Our results allow us to propose that this novel SdAmy as an alternative amylase that could be used in processes involving enzymes that act at moderate temperatures.