AUTHOR=Du Juan , Dong Jianjun , Du Songjie , Zhang Kun , Yu Junhong , Hu Shumin , Yin Hua 

TITLE=Understanding Thermostability Factors of Barley Limit Dextrinase by Molecular Dynamics Simulations

JOURNAL=Frontiers in Molecular Biosciences

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/molecular-biosciences/articles/10.3389/fmolb.2020.00051

DOI=10.3389/fmolb.2020.00051

ISSN=2296-889X

ABSTRACT=<p>Limit dextrinase (LD) is the only endogenous starch-debranching enzyme in barley (<italic>Hordeum vulgare</italic>, <italic>Hv</italic>), which is the key factor affecting the production of a high degree of fermentation. Free LD will lose its activity in the mashing process at high temperature in beer production. However, there remains a lack of understanding on the factor affecting the themostability of <italic>Hv</italic>LD at the atomic level. In this work, the molecular dynamics simulations were carried out for <italic>Hv</italic>LD to explore the key factors affecting the thermal stability of LD. The higher value of root mean square deviation (RMSD), radius of gyration (<italic>R</italic><sub>g</sub>), and surface accessibility (SASA) suggests the instability of <italic>Hv</italic>LD at high temperatures. Intra-protein hydrogen bonds and hydrogen bonds between protein and water decrease at high temperature. Long-lived hydrogen bonds, salt bridges, and hydrophobic contacts are lost at high temperature. The salt bridge interaction analysis suggests that these salt bridges are important for the thermostability of <italic>Hv</italic>LD, including E568–R875, D317–R378, D803–R884, D457–R214, D468–R395, D456–R452, D399–R471, and D541–R542. Root mean square fluctuation (RMSF) analysis identified the thermal-sensitive regions of <italic>Hv</italic>LD, which will facilitate enzyme engineering of <italic>Hv</italic>LD for enhanced themostability.</p>