TY - JOUR

T1 - Identification of an Amylomaltase from the Halophilic Archaeon Haloquadratum walsbyi by Functional Metagenomics: Structural and Functional Insights

AU - Leoni, Claudia

AU - Manzari, Caterina

AU - Hai, Tran

AU - Golyshin, Peter

AU - Pesole, Graziano

AU - Volpicella, Mariateresa

AU - Ceci, Luigi R.

PY - 2022/1/7

Y1 - 2022/1/7

N2 - Amylomaltases are prokaryotic 4-α-glucanotransferases of the GH77 family. Thanks to the ability to modify starch, they constitute a group of enzymes of great interest for biotechnological applications. In this work we report the identification, by means of a functional metagenomics screening of the crystallization waters of the saltern of Margherita di Savoia (Italy), of an amylomaltase gene from the halophilic archaeon Haloquadratum walsbyi, and its expression in Escherichia coli cells. Sequence analysis indicated that the gene has specific insertions yet unknown in homologous genes in prokaryotes, and present only in amylomaltase genes identified in the genomes of other H. walsbyi strains. The gene is not part of any operon involved in the metabolism of maltooligosaccharides or glycogen, as it has been found in bacteria, making it impossible currently to assign a precise role to the encoded enzyme. Sequence analysis of the H. walsbyi amylomaltase and 3D modelling showed a common structure with homologous enzymes characterized in mesophilic and thermophilic bacteria. The recombinant H. walsbyi enzyme showed starch transglycosylation activity over a wide range of NaCl concentrations, with maltotriose as the best acceptor substrate compared to other maltooligosaccharides. This is the first study of an amylomaltase from a halophilic microorganism.

AB - Amylomaltases are prokaryotic 4-α-glucanotransferases of the GH77 family. Thanks to the ability to modify starch, they constitute a group of enzymes of great interest for biotechnological applications. In this work we report the identification, by means of a functional metagenomics screening of the crystallization waters of the saltern of Margherita di Savoia (Italy), of an amylomaltase gene from the halophilic archaeon Haloquadratum walsbyi, and its expression in Escherichia coli cells. Sequence analysis indicated that the gene has specific insertions yet unknown in homologous genes in prokaryotes, and present only in amylomaltase genes identified in the genomes of other H. walsbyi strains. The gene is not part of any operon involved in the metabolism of maltooligosaccharides or glycogen, as it has been found in bacteria, making it impossible currently to assign a precise role to the encoded enzyme. Sequence analysis of the H. walsbyi amylomaltase and 3D modelling showed a common structure with homologous enzymes characterized in mesophilic and thermophilic bacteria. The recombinant H. walsbyi enzyme showed starch transglycosylation activity over a wide range of NaCl concentrations, with maltotriose as the best acceptor substrate compared to other maltooligosaccharides. This is the first study of an amylomaltase from a halophilic microorganism.

KW - 4-Α-glucanotransferase

KW - Archaea

KW - Functional Metagenomics

KW - Halophile

KW - Haloquadratum Walsbyi

KW - Saltern

KW - amylomaltase

U2 - 10.3390/life12010085

DO - 10.3390/life12010085

M3 - Article

VL - 12

JO - Life

JF - Life

SN - 2075-1729

IS - 1

ER -