Versatile biotechnological applications of amylosucrase, a novel glucosyltransferase

Abstract

Amylosucrase (AS; EC 2.4.1.4) is an enzyme that has great potential in the biotechnology and food industries, due to its multifunctional enzyme activities. It can synthesize α-1,4-glucans, like amylose, from sucrose as a sole substrate, but importantly, it can also utilize various other molecules as acceptors. In addition, AS produces sucrose isomers such as turanose and trehalulose. It also efficiently synthesizes modified starch with increased ratios of slow digestive starch and resistant starch, and glucosylated functional compounds with increased water solubility and stability. Furthermore, AS produces turnaose more efficiently than other carbohydrate-active enzymes. Amylose synthesized by AS forms microparticles and these can be utilized as biocompatible materials with various bio-applications, including drug delivery, chromatography, and bioanalytical sciences. This review not only compares the gene and enzyme characteristics of microbial AS, studied to date, but also focuses on the applications of AS in the biotechnology and food industries.

Keywords: Amylose; Amylosucrase; Enzymatically modified starch; Transglycosylation; Turanose.

Fig. 1

(A) The deduced amino acid sequences for various microbial AS. The 3 conserved regions related to the dimerization are surrounded by dotted boxes. (B) The three-dimensional architecture of AS. The secondary and three-dimensional structures are based on NpAS (PDB code: 1G5A), and the active pocket is indicated by a white dotted circle. (C) The phylogenetic analysis of microbial AS. The same colors are used throughout the figure to indicate the different structures: domain N (gray), domain A (red), domain B (green), domain B′ (purple), domain C (yellow)

Fig. 2

(A) Schematic illustration representing the enzymatic synthesis of AMPs and SEM image of the amyulose microparticles generated from the reaciton. The scale bar is 2 μm. (Lim et al., 2014). (B) Turbidity of the reaction solution as a function of the reaction time during the self-assembly of AMPs in the absence (control) and presence of different fatty acids (BA: butanoic acid, HA: hexanoic acid, OA: octanoic acid). Digital images of the reaction tubes corresponding to each condition after (i) 12 h and (ii) 24 h of the self-assembly reactions are shown below (Lim et al., 2016b). (c) SEM images (left) and size distribution (right) of AMPs formed with varying concentrations of lecithin from 0.005% to 0.5% (w/v) (Letona et al., 2019)

Fig. 3

(A) SEM image of beta-carotene-encapsulated amylose microparticles. The scale bar is 10 μm (Letona et al., 2017). (B) Purification efficiency of superparamagnetic amylose microparticles (SAMPs) for target protein, MBP-GFP, from cell lysate after three rounds of recycling. The numbers (1-3) represent the number of recycling (Lim et al., 2015). (C) SEM image of SAMPs synthesized with Dex@IONPs. The inset in the upper right corner shows the size distribution of the histogram of the SAMPs. (D) The average diameter of the SAMPs formed with varying concentrations of Dex@IONPs. (E) The capture efficiency of commercial polystyrene magnetic beads (PSMBs) and superparamagnetic amylose magnetic beads (SAMBs) for target bacteria, E. coli O157:H7, with concentrations ranging from 10² to 10⁶ CFU/mL in milk samples. (F) The capture specificity of immuno-SAMBs for target bacteria. Non-specific binding of the immuno-SAMBs with non-target bacteria was negligible (Luo et al., 2018a)