AUTHOR=Zhang Guoyan , An Yingfeng , Parvez Amreesh , Zabed Hossain M. , Yun Junhua , Qi Xianghui 

TITLE=Exploring a Highly D-Galactose Specific L-Arabinose Isomerase From Bifidobacterium adolescentis for D-Tagatose Production

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2020.00377

DOI=10.3389/fbioe.2020.00377

ISSN=2296-4185

ABSTRACT=<p><sc>D</sc>-Galactose-specific <sc>L</sc>-arabinose isomerase (L-AI) would have much potential for the enzymatic conversion of <sc>D</sc>-Galactose into D-tagatose, while most of the reported L-AIs are <sc>L</sc>-arabinose specific. This study explored a highly <sc>D</sc>-Galactose-specific L-AI from <italic>Bifidobacterium adolescentis</italic> (BAAI) for the production of D-tagatose. In the comparative protein-substrate docking for <sc>D</sc>-Galactose and <sc>L</sc>-arabinose, BAAI showed higher numbers of hydrogen bonds in <sc>D</sc>-Galactose-BAAI bonding site than those found in <sc>L</sc>-arabinose-BAAI bonding site. The activity of BAAI was 24.47 U/mg, and it showed good stability at temperatures up to 65°C and a pH range 6.0–7.5. The <italic>K</italic><sub>m</sub>, <italic>V</italic><sub>max</sub>, and <italic>K</italic><sub>cat</sub>/<italic>K</italic><sub>m</sub> of BAAI were found to be 22.4 mM, 489 U/mg and 9.3 mM<sup>–1</sup> min<sup>–1</sup>, respectively for <sc>D</sc>-Galactose, while the respective values for <sc>L</sc>-arabinose were 40.2 mM, 275.1 U/mg, and 8.6 mM<sup>–1</sup> min<sup>–1</sup>. Enzymatic conversion of <sc>D</sc>-Galactose into D-tagatose by BAAI showed 56.7% conversion efficiency at 55°C and pH 6.5 after 10 h.</p>