amylopectin and panose

A bottleneck in enzymatic starch hydrolysis, like in biofuel industry, is relatively slow degradation of branched structures compared to linear ones. This research aimed to evaluate glucoamylases for their activity towards branched gluco-oligosaccharides. The activity of seven modified glucoamylases and two homologs was compared to that of a reference glucoamylase obtained from a commercial enzyme cocktail 'Distillase® SSF'. All enzymes were evaluated for their activity towards panose (glc(α1-6)glc(α1-4)glc), pullulan and a purified branched gluco-oligosaccharide with a degree of polymerisation of 5 (bDP5) identified as glc(α1-4)[glc(α1-4)glc(α1-6)]glc(α1-4)glc. The enzymes degraded bDP5 differently, which was mainly due to variation in their capability to cleave α-(1→6)-linked or the α-(1→4)-linked glucosyl residue at the non-reducing end of the branched glucosyl residue. By comparing the enzyme activity towards bDP5 with those towards panose and pullulan, it was suggested that the activity towards bDP5 could be estimated only when the activity towards both commercial substrates was evaluated.

Topics: Amylopectin; Carbohydrate Sequence; Glucan 1,4-alpha-Glucosidase; Glucans; Glucose; Hypocrea; Oligosaccharides

To gain insight into the molecular details and hydration of amylopectin, the five constituting trisaccharides have been chemically synthesized as their methyl alpha-glycosides. All five trisaccharides were subjected to 950 MHz NMR spectroscopy for complete assignment and nanosecond molecular dynamics trajectories were calculated to study the structure and dynamics of the trisaccharides in aqueous solution. Systematic analysis of the simulation data revealed several examples of bridging water molecules playing an important role in the stabilization of specific amylopectin conformations, which was also supported by the experimental NMR data such as interresidue NOE's and heteronuclear scalar couplings between nuclei from neighboring residues. Although alpha-maltotriose, alpha-iso-maltotriose, alpha-panose and alpha-isopanose are relatively well characterized structures, the study also includes one less characterized trisaccharide with the structure alphaGlcp(1-->4)alphaGlcp(1-->6)alphaGlcp. This trisaccharide, tentatively labelled alpha-forkose, is located at the branch point of amylopectin, forking the amylopectin into two strands that align into double-helical segments. The results show that the conformation of alpha-forkose takes a natural bend form which fits well into the structure of the double-helical segment of amylopectin. As the only trisaccharide in this study the structure of alpha-forkose is not significantly influenced by the hydration. In contrast, alpha-isopanose takes a restricted, but rather extended form due to an exceptionally strong localized water density. The two homo-linkage oligomers, alpha-maltotriose and alpha-iso-maltotriose, showed to be the most extended and the most flexible trimers, respectively, providing regular structure for crystalline domains and maximum linker flexibility for amorphous domains.

Topics: Amylopectin; Carbohydrate Conformation; Carbohydrate Sequence; Diffusion; Glucans; Glucose; Magnetic Resonance Spectroscopy; Maltose; Models, Molecular; Trisaccharides