Cold-Active Starch-Degrading Enzymes from a Cold and Alkaline Greenland Environment: Role of Ca2+ Ions and Conformational Dynamics in Psychrophilicity

• Type: Article in International Scientific Journal
• Date: 2025

Authors

Bendtsen, MK (Author) Other; Nowak, JS (Author) Other; Paiva, P (Author) Other; Hernández, ML (Author) Other; Ferreira, P (Author) FCUP; Pedersen, JS (Author) Other; Bekker, NS (Author) Other; Viezzi, E (Author) Other; Bisiak, F (Author) Other; Brodersen, DE (Author) Other; Pedersen, LH (Author) Other; Zervas, A (Author) Other; Pedro A Fernandes (Author) FCUP; Ramos, MJ (Author) Other; Stougaard, P (Author) Other; Thogersen, MS (Author) Other; Otzen, DE (Author) Other

Journal

Title: Biomolecules

Vol. 15

Final page: 415

ISSN: 2218-273X

Publisher: MDPI

Indexing

ISI Web of Knowledge - 0 Citations

Scopus - 0 Citations

Other information

Authenticus ID: P-018-BS0

DOI: 10.3390/biom15030415

Abstract (EN): Cold-active enzymes hold promise for energy-efficient processes. Amylases are widely used in household and industrial applications, but only a few are cold-active. Here we describe three novel secreted amylases, Rho13, Ika2 and I3C6, all from bacteria growing in the cold and alkaline ikaite columns in Greenland. They all hydrolyzed starch to smaller malto-oligomers, but only Rho13 and Ika2 hydrolyzed cyclodextrins, and only Ika2 displayed transglycosylation activity. Ika2 forms a stable dimer, while both Rho13 and I3C6 are mainly monomeric. They all have optimal active temperatures around 30-35 degrees C and significant enzymatic activity below 20 degrees C, but Rho13 and I3C6 had an alkaline optimal pH, while Ika2 was markedly acidophilic. They showed complex dependence on Ca2+ concentration, with the activity of Rho13 and I3C6 following a bell-shaped curve and Ika2 being unaffected; however, removal of Ca2+ reduced the stability of all three enzymes. Loss of structure occurred well above the temperature of optimal activity, showing the characteristic psychrophilic divorce between activity and stability. MD simulations showed that Ika2 did not have a well-defined Ca2+ binding site, while Rho13 and I3C6 both maintained one stably bound Ca2+ ion. We identified psychrophilic features as higher levels of backbone fluctuations compared to mesophilic counterparts, based on a lower number of internal hydrogen bonds and salt bridges. This increased fluctuation was also found in regions outside the active site and may provide easier substrate access and accommodation, as well as faster barrier transitions. Our work sheds further light on the many ways in which psychrophilic enzymes adapt to increased catalysis at lower temperatures.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 31