Action pattern of porcine pancreatic alpha-amylase on three different series of beta-maltooligosaccharide glycosides

Interfacial Catalysis during Amylolytic Degradation of Starch Granules: Current Understanding and Kinetic Approaches

Enzymatic hydrolysis of starch granules forms the fundamental basis of how nature degrades starch in plant cells, how starch is utilized as an energy resource in foods, and develops efficient, low-cost saccharification of starch, such as bioethanol and sweeteners. However, most investigations on starch hydrolysis have focused on its rates of degradation, either in its gelatinized or soluble state. These systems are inherently more well-defined, and kinetic parameters can be readily derived for different hydrolytic enzymes and starch molecular structures. Conversely, hydrolysis is notably slower for solid substrates, such as starch granules, and the kinetics are more complex. The main problems include that the surface of the substrate is multifaceted, its chemical and physical properties are ill-defined, and it also continuously changes as the hydrolysis proceeds. Hence, methods need to be developed for analyzing such heterogeneous catalytic systems. Most data on starch granule degradation are obtained on a long-term enzyme-action basis from which initial rates cannot be derived. In this review, we discuss these various aspects and future possibilities for developing experimental procedures to describe and understand interfacial enzyme hydrolysis of native starch granules more accurately.

Maltooligosaccharides: Properties, Production and Applications

Maltooligosaccharides (MOS) are homooligosaccharides that consist of 3-10 glucose molecules linked by α-1,4 glycosidic bonds. As they have physiological functions, they are commonly used as ingredients in nutritional products and functional foods. Many researchers have investigated the potential applications of MOS and their derivatives in the pharmaceutical industry. In this review, we summarized the properties and methods of fabricating MOS and their derivatives, including sulfated and non-sulfated alkylMOS. For preparing MOS, different enzymatic strategies have been proposed by various researchers, using α-amylases, maltooligosaccharide-forming amylases, or glycosyltransferases as effective biocatalysts. Many researchers have focused on using immobilized biocatalysts and downstream processes for MOS production. This review also provides an overview of the current challenges and future trends of MOS production.

Ring-Opening of Cyclodextrins: An Efficient Route to Pure Maltohexa-, Hepta-, and Octaoses

Many preparations of maltooligosaccharides have been described in literature, essentially using enzymatic or biotechnological processes. These compounds, derived from starch, are well-known as prebiotic agents. The use of maltohexa-, hepta-, and octaoses as synthons in organic synthesis was also well documented in literature. They can indeed be obtained as single compounds by the cyclodextrins’ ring-opening. This reaction has been studied for many years, varying the protecting and functional groups and the reaction conditions, leading to functionalized oligomaltoses. These compounds are of wide interest in various fields. They have a strong potential as scaffolds for multivalence in chemobiology, as building blocks for the production of biomimetic pseudo-glycopeptides, as well as monomers for the preparation of materials. In view of the importance of these oligomaltoses, this review focuses on the different methodologies allowing access to them via chemical and enzymatic ring-opening of cyclodextrins.

Colorado potato beetle alpha-amylase: Purification, action pattern and subsite mapping for exploration of active centre

Colorado potato beetle is an invasive insect herbivore and one of the most challenging agricultural pests globally. This study is the first characterization of the active centre of Colorado potato beetle (Leptinotarsa decemlineata) α-amylase (LdAmy). Bond cleavage frequency values for LdAmy were determined by HPLC product analysis on a chromophore labelled maltooligomer substrate series. Binding energies between amino acid moieties of subsites and glucose residues of substrate were calculated. Active site contains six subsites in the binding region of LdAmy; four glycone- (-4, -3, -2, -1) and two aglycone-binding sites (+1, +2). Subsite map calculation resulted in apparent binding energies -11.8 and - 11.0 kJ/mol for subsites (+2) and (-3), respectively, which revealed very favorable interactions at these positions. Structures of binding sites of LdAmy and mammalian α-amylases show similarity, but there are variations in the binding energies at subsite (-2) and (-4). Differences were interpreted by comparison of amino acid sequences of human salivary α-amylase (HSA) and porcine pancreatic α-amylase (PPA) and two insect (Leptinotarsa decemlineata and Tenebrio molitor) enzymes. The observed substitution of positively charged His305 in HSA at subsite (-2) with an acidic Asp in LdAmy in the same position may explain the obtained energy reduction.

Cooperation of enzymes involved in carbohydrate digestion of Colorado potato beetle (Leptinotarsa decemlineata, Say)

Colorado potato beetle (Leptinotarsa decemlineata, Say) is the main pest of Solanaceae and its survival is mainly dependent on the carbohydrate digestion. Characterizing the gut enzymes may help us with finding effective inhibitors for plant protection. Activity measurements revealed that gut extracts contain α- and β-glucosidase in addition to α-amylase. For larvae, amylase activity was detected only in gut saturated with nutrients. Leptinotarsa decemlineata α-amylase (LDAmy) had optimum pH of 6.0 and was active under 30-40°C temperature measured on a selective α-amylase substrate, 2-chloro-4-nitrophenyl-4-O-α-D-galactopyranosyl-maltoside. HPLC analysis demonstrated dimer, trimer, and tetramer reducing end amylolytic products from 2-chloro-4-nitrophenyl-maltoheptaoside substrate in similar ratio than that of during porcine pancreatic α-amylase (PPA) catalyzed hydrolysis. The 4,6-O-benzylidene-modified substrate (BzG7PNP) is very stable toward hydrolysis by exo-glycosidases, therefore is very useful to monitor the digestion catalyzed by α-amylases exclusively. Similarly to PPA active site, three glycon and two aglycon binding sites are suggested for LDAmy based on the pattern of early hydrolysis products of BzG7PNP. The observed similarity between LDAmy and PPA raises the possibility of using known inhibitors of mammalian α-amylases to protect the potato plant from attack of Colorado potato beetle.

Enzymatic synthesis of 4-methylumbelliferyl (1-->3)-beta-D-glucooligosaccharides-new substrates for beta-1,3-1,4-D-glucanase

The transglycosylation reactions catalyzed by beta-1,3-D-glucanases (laminaranases) were used to synthesize a number of 4-methylumbelliferyl (MeUmb) (1-->3)-beta-D-gluco-oligosaccharides having the common structure [beta-D-Glcp-(1-->3)](n)-beta-D-Glcp-MeUmb, where n=1-5. The beta-1,3-D-glucanases used were purified from the culture liquid of Oerskovia sp. and from a homogenate of the marine mollusc Spisula sachalinensis. Laminaran and curdlan were used as (1-->3)-beta-D-glucan donor substrates, while MeUmb-beta-D-glucoside (MeUmbGlcp) was employed as a transglycosylation acceptor. Modification of [beta-D-Glcp-(1-->3)](2)-beta-D-Glcp-MeUmb (MeUmbG(3)) gives 4,6-O-benzylidene-D-glucopyranosyl or 4,6-O-ethylidene-D-glucopyranosyl groups at the non-reducing end of artificial oligosaccharides. The structures of all oligosaccharides obtained were solved by 1H and 13C NMR spectroscopy and electrospray tandem mass spectrometry. The synthetic oligosaccharides were shown to be substrates for a beta-1,3-1,4-D-glucanase from Rhodothermus marinus, which releases MeUmb from beta-di- and beta-triglucosides and from acetal-protected beta-triglucosides. When acting upon substrates with d.p.>3, the enzyme exhibits an endolytic activity, primarily cleaving off MeUmbGlcp and MeUmbG(2).

Subsite mapping of human salivary alpha-amylase and the mutant Y151M

This study characterizes the substrate-binding sites of human salivary alpha-amylase (HSA) and its Y151M mutant. It describes the first subsite maps, namely, the number of subsites, the position of cleavage sites and apparent subsite energies. The product pattern and cleavage frequencies were determined by high-performance liquid chromatography, utilizing a homologous series of chromophore-substituted maltooligosaccharides of degree of polymerization 3-10 as model substrates. The binding region of HSA is composed of four glycone and three aglycone-binding sites, while that of Tyr151Met is composed of four glycone and two aglycone-binding sites. The subsite maps show that Y151M has strikingly decreased binding energy at subsite (+2), where the mutation has occurred (-2.6 kJ/mol), compared to the binding energy at subsite (+2) of HSA (-12.0 kJ/mol).

Subsite mapping of the binding region of alpha-amylases with a computer program

A computer program has been evaluated for subsite map calculations of depolymerases. The program runs in windows and uses the experimentally determined bond cleavage frequencies (BCFs) for determination of the number of subsites, the position of the catalytic site and for calculation of subsite binding energies. The apparent free energy values were optimized by minimization of the differences of the measured and calculated BCF data. The program called suma (SUbsite Mapping of alpha-Amylases) is freely available for research and educational purposes via the Internet (E-mail: gyemant@tigris.klte.hu). The advantages of this program are demonstrated through alpha-amylases of different origin, e.g. porcine pancreatic alpha-amylase (PPA) studied in our laboratory, in addition to barley and rice alpha-amylases published in the literature. Results confirm the popular 'five subsite model' for PPA with three glycone and two aglycone binding sites. Calculations for barley alpha-amylase justify the '6 + 2 + (1) model' prediction. The binding area of barley alpha-amylase is composed of six glycone, two aglycone binding sites followed by a barrier subsite at the reducing end of the binding site. Calculations for rice alpha-amylase represent an entirely new map with a '(1) + 2 + 5 model', where '(1)' is a barrier subsite at the nonreducing end of the binding site and there are two glycone and five aglycone binding sites. The rice model may be reminiscent of the action of the bacterial maltogenic amylase, that is, suggesting an exo-mechanism for this enzyme.

Action pattern and subsite mapping of Bacillus licheniformis alpha-amylase (BLA) with modified maltooligosaccharide substrates

This study represents the first characterisation of the substrate-binding site of Bacillus licheniformis alpha-amylase (BLA). It describes the first subsite map, namely, number of subsites, apparent subsite energies and the dual product specificity of BLA. The product pattern and cleavage frequencies were determined by high-performance liquid chromatography, utilising a homologous series of chromophore-substituted maltooligosaccharides of degree of polymerisation 4-10 as model substrates. The binding region of BLA is composed of five glycone, three aglycone-binding sites and a 'barrier' subsite. Comparison of the binding energies of subsites, which were calculated with a computer program, shows that BLA has similarity to the closely related Bacillus amyloliquefaciens alpha-amylase.

Chemoenzymatic synthesis of 2-chloro-4-nitrophenyl beta-maltoheptaoside acceptor-products using glycogen phosphorylase b

In the present work, we aimed at developing a chemoenzymatic procedure for the synthesis of beta-maltooligosaccharide glycosides. The primer in the enzymatic reaction was 2-chloro-4-nitrophenyl beta-maltoheptaoside (G(7)-CNP), synthesised from beta-cyclodextrin using a convenient chemical method. CNP-maltooligosaccharides of longer chain length, in the range of DP 8-11, were obtained by a transglycosylation reaction using alpha-D-glucopyranosyl-phosphate (G-1-P) as a donor. Detailed enzymological studies revealed that the conversion of G(7)-CNP catalysed by rabbit skeletal muscle glycogen phosphorylase b (EC 2.4.1.1) could be controlled by acarbose and was highly dependent on the conditions of transglycosylation. More than 90% conversion of G(7)-CNP was achieved through a 10:1 donor-acceptor ratio. Tranglycosylation at 37 degrees C for 30 min with 10 U enzyme resulted in G(8-->12)-CNP oligomers in the ratio of 22.8, 26.6, 23.2, 16.5, and 6.8%, respectively. The reaction pattern was investigated using an HPLC system. The preparative scale isolation of G(8-->11)-CNP glycosides was achieved on a semipreparative HPLC column. The productivity of the synthesis was improved by yields up to 70-75%. The structures of the oligomers were confirmed by their chromatographic behaviours and MALDI-TOF MS data.

Examination of the active sites of human salivary alpha-amylase (HSA)

The action pattern of human salivary amylase (HSA) was examined by utilising as model substrates 2-chloro-4-nitrophenyl (CNP) beta-glycosides of maltooligosaccharides of dp 4-8 and some 4-nitrophenyl (NP) derivatives modified at the nonreducing end with a 4,6-O-benzylidene (Bnl) group. The product pattern and cleavage frequency were investigated by product analysis using HPLC. The results revealed that the binding region in HSA is longer than five subsites usually considered in the literature and suggested the presence of at least six subsites; four glycone binding sites (-4, -3, -2, -1) and two aglycone binding sites (+1, +2). In the ideal arrangement, the six subsites are filled by a glucosyl unit and the release of maltotetraose (G4) from the nonreducing end is dominant. The benzylidene group was also recognisable by subsites (-3) and (-4). The binding modes of the benzylidene derivatives indicated a favourable interaction between the Bnl group and subsite (-3) and an unfavourable one with subsite (-4). Thus, subsite (-4) must be more hydrophylic than hydrophobic. As compared with the action of porcine pancreatic alpha-amylase (PPA) on the same substrates, the results showed differences in the three-dimensional structure of active sites of HSA and PPA.

Amylose chain behavior in an interacting context. III. Complete occupancy of the AMY2 barley alpha-amylase cleft and comparison with biochemical data

In the first two papers of this series, the tools necessary to evaluate substrate ring deformations were developed, and then the modeling of short amylose fragments (maltotriose and maltopentaose) inside the catalytic site of barley alpha-amylase was performed. In this third paper, this docking has been extended to the whole catalytic cleft. A systematic approach to extend the substrate was used on the reducing side from the previous enzyme/pentasaccharide complex. However, due to the lack of an obvious subsite at the nonreducing side, an alternate protocol has been chosen that incorporates biochemical information on the enzyme and features on the substrate shape as well. As a net result, ten subsites have been located consistent with the distribution of Ajandouz et al. (E. H. Ajandouz, J. Abe, B. Svensson, and G. Marchis-Mouren, Biochimica Biophysica Acta, 1992, Vol. 1159, pp. 193-202) and corresponding binding energies were estimated. Among them, two extreme subsites (-6) and (+4), with stacking residues Y104 and Y211, respectively, have strong affinities with glucose rings added to the substrate. No other deformation has been found for the new glucose rings added to the substrate; therefore, only ring A of the DP 10 fragment has a flexible form when interacting with the inner stacking residues Y51. Global conservation of the helical shape of the substrate can be postulated in spite of its significant distortion at subsite (-1).

Synthesis of chromogenic substrates of alpha-amylases on a cyclodextrin basis

One-pot acetylation and subsequent partial acetolysis of alpha-, beta- and gamma-cyclodextrins resulted in crystalline peracetylated malto-hexaose, -heptaose, and -octaose, respectively. Prolonged acetolysis of beta-cyclodextrin gave a mixture of acetylated maltooligosaccharides, from which peracetylated malto-triose, -tetraose, and -pentaose were isolated. The acetylated oligosaccharides were converted into alpha-acetobromo derivatives, and then transformed into 4-nitrophenyl and 2-chloro-4-nitrophenyl beta-glycosides. From the 4-nitrophenyl glycosides 4,6-O-benzylidene derivatives were prepared, which were used together with the free glycosides as substrates of porcine pancreatic alpha-amylase.