科研之友
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摘要
Staphylothermus marinus maltogenic amylase (SMMA) is a novel extreme thermophile maltogenic amylase with an optimal temperature of 100 degrees C, which hydrolyzes alpha-(1-4)-glycosyl linkages in cyclodextrins and in linear malto-oligosaccharides. This enzyme has along N-terminal extension that is conserved among archaic hyperthermophilic amylases but is not found in other hydrolyzing enzymes from the glycoside hydrolase 13 family. The SMMA crystal structure revealed that the N-terminal extension forms an N%26apos; domain that is similar to carbohydrate-binding module 48, with the strand-loop-strand region forming a part of the substrate binding pocket with several aromatic residues, including Phe-95, Phe-96, andTyr-99. A structural comparison with conventional cyclodextrin-hydrolyzing enzymes revealed a striking resemblance between the SMMA N%26apos; domain position and the dimeric N domain position in bacterial enzymes. This result suggests that extremophilic archaea that live at high temperatures may have adopted a novel domain arrangement that combines all of the substrate binding components within a monomeric subunit. The SMMA structure provides a molecular basis for the functional properties that are unique to hyperthermophile malto-genic amylases from archaea and that distinguish SMMA from moderate thermophilic or mesophilic bacterial enzymes.
- 出版日期2012-3-9
- 单位长春大学; 中国科学技术大学
