Human Salivary Α-amylase Research Articles

The use of starch azure for measurement of alpha-amylase activity

Despite being widely used, there is no standard protocol for α-amylase activity measurement with starch azure substrate. Boiling pre-treatment of starch azure suspension increased the reaction rate of hydrolysis catalysed by human salivary α-amylase (HSA) or porcine pancreatic α-amylase (PPA) and the sensitivity of spectrophotometric activity measurement has been improved. Kinetic constants, KM, and vmax, obtained from parallel isothermal titration calorimetric (ITC) measurements on natural and starch azure revealed, that the blue starch derivative does not differ significantly from its natural counterpart from kinetic point of view. Interestingly, substrate inhibition was observed in starch azure hydrolysis characterised by dissociation constants 49 mg/mL and 16.4 mg/mL for HSA and PPA, respectively. In this work a new protocol has been suggested for α-amylase activity measurement using boiled insoluble starch azure as substrate at 5 mg/mL concentration.

Oleanolic acid and ursolic acid as potential inhibitors of human salivary α-amylase: insights from in vitro assays and in silico simulations.

It is known that inhibiting α-amylase, an important enzyme in digestion of starch and glycogen, is a useful strategy for treating disorders in carbohydrate uptake. Two natural components distributed in many fruits and plants, oleanolic acid and ursolic acid, are endowed with important pharmacological activities and wide therapeutic possibilities. Until now, only a tiny fraction of their applications have been identified and exploited. Our in vitro inhibition studies demonstrated that oleanolic acid and ursolic acid non-competitively inhibit the activity and function of human salivary α-amylase. The molecular simulations revealed that oleanolic acid and ursolic acid interact with amino acid residues within the binding pocket of human salivary α-amylase, among which the side chain of Arg195 and Asp 197 was supposed to be important in imparting the inhibitory activity of triterpenoids. The present work will provide meaningful information for future development of functional drugs for the treatment of disorders in carbohydrate metabolism. Graphical abstract This work is valuable for providing a deeper insight into the interaction mechanism of oleanolic acid and ursolic acid with α-amylase.

HPLC Method for Measurement of Human Salivary \u03b1-Amylase Inhibition by Aqueous Plant Extracts

Control of hyperglycemia is an important treatment in metabolic disorders such as type II diabetes and obesity. α-Amylase, as the first enzyme of glucose release from dietary polysaccharides, is a potential target to identify new sources of novel anti-obesity and anti-diabetic drugs. In this work, different herbal extracts as α-amylase inhibitors were studied by measuring the rate of the cleavage of a maltooligomer substrate 2-chloro-4-nitrophenyl-β-D-maltoheptoside. Measurement of chromophore containing products after reversed phase HPLC separation was used for α-amylase activity measurement. Rates of hydrolysis catalysed by human salivary α-amylase were determined in the presence and absence of lyophilised water extracts of eleven herbs. Remarkable bioactivities were found for extracts of Cinnamomum zeylanicum Blume (bark), Camellia sinensis L. (leaf), Ribes nigrum L. (leaf), Laurus nobilis L. (leaf), Vaccinium macrocarpon Aiton (fruit) and Syzygium aromaticum L. (bud). Determined IC50 values were in 0.017–41 μg/ml range for these six selected plant extracts. Our results confirm the applicability of this HPLC-based method for the quick and reliable comparison of plants as α-amylase inhibitors.

Flexible immunosensor for the detection of salivary α-amylase in body fluids

The development of a portable testing device for detecting Human Salivary α-Amylase (HSA) is very timely since such an enzyme is a valuable biomarker for diagnosing many diseases and monitoring the human stress. We show that an easy-to-use and robust device like the Quartz-Crystal Microbalance (QCM) can be a suitable platform for HSA sensing with a limit of detection of 1µg/mL (77 U/L). The functionalization of the gold surface is realized by the Photochemical Immobilization Technique (PIT), a powerful and simple method based on an appropriate UV-activation of antibodies. The resulting QCM-based immunosensor allows one to detect HSA in saliva by simple dilution and one-step protocol, whereas the measurement of HSA content in body fluids like urine and serum could be carried out by introducing an additional step consisting of analyte ballasting through the formation of sandwich complexes, which pushes the limit of detection to less than 10 U/L. The validation of the one-step protocol with a standard laboratory method like Phadebas test demonstrates the reliability of the proposed immunosensors, which can be applied to the amylase concentration in body fluids like blood serum and urine for which the physiological level is above 20 U/L.

Inhibition of α-Amylases by Condensed and Hydrolysable Tannins: Focus on Kinetics and Hypoglycemic Actions.

The aim of the present study was to compare the in vitro inhibitory effects on the salivary and pancreatic α-amylases and the in vivo hypoglycemic actions of the hydrolysable tannin from Chinese natural gall and the condensed tannin from Acacia mearnsii. The human salivary α-amylase was more strongly inhibited by the hydrolysable than by the condensed tannin, with the concentrations for 50% inhibition (IC50) being 47.0 and 285.4 μM, respectively. The inhibitory capacities of both tannins on the pancreatic α-amylase were also different, with IC50 values being 141.1 μM for the hydrolysable tannin and 248.1 μM for the condensed tannin. The kinetics of the inhibition presented complex patterns in that for both inhibitors more than one molecule can bind simultaneously to either the free enzyme of the substrate-complexed enzyme (parabolic mixed inhibition). Both tannins were able to inhibit the intestinal starch absorption. Inhibition by the hydrolysable tannin was concentration-dependent, with 53% inhibition at the dose of 58.8 μmol/kg and 88% inhibition at the dose of 294 μmol/kg. For the condensed tannin, inhibition was not substantially different for doses between 124.4 μmol/kg (49%) and 620 μmol/kg (57%). It can be concluded that both tannins, but especially the hydrolysable one, could be useful in controlling the postprandial glycemic levels in diabetes.

A glycoprotein α-amylase inhibitor from Withania somnifera differentially inhibits various α-amylases and affects the growth and development of Tribolium castaneum.

Identification and characterisation of plant defensive molecules enrich our resources to design crop protection strategies. In particular, plant-derived proteinaceous inhibitor(s) of insect digestive enzymes appear to be a safe, sustainable and attractive option. A glycoprotein having non-competitive α-amylase inhibitory activity with a molecular weight of 8.3 kDa was isolated and purified from seeds of Withania somnifera α-amylase inhibitor (WSAI). Its mass spectrometry analysis revealed 59% sequence coverage with Wrightide II-type α-amylase inhibitor from Wrightia religiosa. A dose-dependent inhibition of α-amylases from Aspergillus oryzae, Bacillus subtilis, Helicoverpa armigera and Tribolium castaneum was recorded. Interestingly, WSAI did not inhibit human salivary α-amylase significantly. When adults of T. castaneum were fed with WSAI (1.6 mg g-1 ), decrease in consumption, growth and efficiency of conversion of ingested food was evident, along with over fourfold increases in feeding deterrence index. A decline in larval residual α-amylase activity after feeding of WSAI resulted in a reduction in longevity of T. castaneum. The study reflects the significance of WSAI in affecting the overall growth and development of T. castaneum. Pre- and post-harvest pest resistive capability makes WSAI a potential candidate for insect pest management. Further, the effectiveness of this inhibitor could be explored either in formulations or through a transgenic approach. © 2016 Society of Chemical Industry.

ZnO nanoparticles and their acarbose-capped nanohybrids as inhibitors for human salivary amylase.

The authors report a controlled synthesis of biocompatible ZnO and acarbose-capped nanohybrids, and examined the inhibition activities of these nanosystems with human salivary α-amylase (HSA) activity. XRD measurements reveal ZnO present in wurtzite phase with hexagonal structure. The average size of ZnO particles for the two studied nanosystems was estimated to lie between 10 to 12 nm using Scherrer equation. These particles depict the onset of absorption at about 320 nm and the band-gap emission at about 370 nm, which are fairly blue shifted as compared with the bulk ZnO and have been understood due to the size quantisation effect. The inhibitory action of thioglycerol capped ZnO nanoparticles (SP1) and acarbose drug (used for diabetes type II) capped ZnO (SP2) for HSA was observed to 61 and72%, respectively. The inhibition activity of the SP1 alone was found to be very similar to that of acarbose and the coating of these particles with drug (SP2) demonstrated an enhancement in inhibition activity of the enzyme by about 30%. From the inhibition studies, it is confirmed that these nanosystems showed better inhibition activity at physiological temperature and pH. These nanosystems are projected to have potential applications in diabetes type II control.

Development of a workflow for screening and identification of α-amylase inhibitory peptides from food source using an integrated Bioinformatics-phage display approach: Case study – Cumin seed

The main objective of this study was to develop an efficient workflow to discover α-amylase inhibitory peptides from cumin seed. A total of 56 unknown peptides was initially found in the cumin seed protein hydrolysate. They were subjected to 2 different in silico screenings and 6 peptides were shortlisted. The peptides were then subjected to in vitro selection using phage display technique and 3 clones (CSP3, CSP4 and CSP6) showed high affinity in binding α-amylase. These clones were subjected to the inhibitory test and only CSP4 and CSP6 exhibited high inhibitory activity. Therefore, these peptides were chemically synthesized for validation purposes. CSP4 exhibited inhibition of bacterial and human salivary α-amylases with IC50 values of 0.11 and 0.04μmol, respectively, whereas CSP6 was about 0.10 and 0.15μmol, respectively. Results showed that the strength of each protocol has been successfully combined as deemed fit to enhance the α-amylase inhibitor peptide discovery.

Simple ITC method for activity and inhibition studies on human salivary α-amylase

Isothermal titration calorimetry (ITC) has an increasing significance in enzyme kinetic studies owing to its general applicability and sensitivity. In the present work, we aimed at developing a simple ITC-based screening procedure for the measurement of human salivary α-amylase (HSA) activity. Reaction of two substrates was studied with three independent methods (ITC, HPLC and spectrophotometry). ITC experiments were made using free and chromophore-containing maltooligomers of different length as substrates. Detailed studies revealed that maltoheptaose or longer oligomers could model properly starch and the presence of aromatic chromophore group did not affect the KM values considerably. It is the first time, when ITC was used to investigate of HSA-catalysed hydrolysis of different substrates (2-chloro-4-nitrophenyl-4-O-α-D-galactopyranosyl-maltoside, maltoheptaose and starch) in the presence of acarbose inhibitor. All measured IC50 values are in micromolar range (0.9, 18.6 and 29.0 μM, respectively) and increased in parallel with the degree of polymerisation of substrates.

Advancing insights on the anti-obesity biochemical mechanism of (−)-epigallocatechin gallate (EGCG) by inhibiting α-amylase activity

The biochemical mechanisms of EGCG against human salivary α-amylase are comprehensively investigated in vitro as well as histological analyses and physiological indexes of obesity mice in vivo after 30 day EGCG oral administration.

Capillary isoelectric focusing with whole column UV detection (CIEF-UV-WCID) to characterize human salivary α-amylase

Capillary isoelectric focusing with whole column UV detection (CIEF-UV-WCID) to characterize human salivary α-amylase

A probabilistic approach to body fluid typing interpretation: an exploratory study on forensic saliva testing

Identifying specific human body fluids and establishing their presence in traces can be crucial to help reconstructing alleged incidents in criminal cases. It is up to the forensic practitioner to test for the presence of body fluids, interpret the test results and draw scientifically supported conclusions that can be used in a court of law. This study presents a Bayesian network for the interpretation of test results for human saliva based on the presence of human salivary α-amylase. The Bayesian network can be used by forensic practitioners as an exploratory tool to form their expert opinion on the presence or absence of saliva in a trace.

Structure of amylase-binding protein A of Streptococcus gordonii: a potential receptor for human salivary α-amylase enzyme.

Amylase-binding protein A (AbpA) of a number of oral streptococci is essential for the colonization of the dental pellicle. We have determined the solution structure of residues 24-195 of AbpA of Streptococcus gordonii and show a well-defined core of five helices in the region of 45-115 and 135-145. (13) Cα/β chemical shift and heteronuclear (15) N-{(1) H} NOE data are consistent with this fold and that the remainder of the protein is unstructured. The structure will inform future molecular experiments in defining the mechanism of human salivary α-amylase binding and biofilm formation by streptococci.

The roles of AMY1 copies and protein expression in human salivary α-amylase activity

Salivary α-amylase (sAA) activity has been extensively investigated in nutrition and psychology. But few studies were performed to assess the role played by sAA gene (AMY1) copies and protein expression in basal and stimulus-induced sAA activity. The sAA activity, amount and AMY1 copy number were determined from 184 saliva samples pre- and post-citric acid stimulation. Our findings showed that citric acid could induce significant increase in sAA activity, total sAA amount, and glycosylated sAA amount, among which the glycosylated sAA amount had the largest response. The correlation analysis showed that AMY1 copy number, total sAA amount and AMY1 copy number×total sAA amount had significantly positive and successively increasing correlations with sAA activity in unstimulated and stimulated saliva, respectively, and furthermore, we observed higher correlations in unstimulated saliva when compared with the corresponding correlations in stimulated saliva. We also observed significant correlations between glycosylated sAA amount and sAA activity in unstimulated and stimulated saliva, respectively. Interestingly, the correlations were higher in stimulated saliva than in unstimulated saliva, and the correlations between glycosylated sAA amount and sAA activity were higher than that of between total sAA amount and sAA activity in stimulated saliva. Moreover, total sAA amount ratio and glycosylated sAA amount ratio showed significantly positive correlation with sAA activity ratio. AMY1 copy number had no correlation with sAA activity ratio. These findings suggested that AMY1 copy number and sAA amount played crucial roles in sAA activity; however, the roles were attenuated after stimulation due to fortified release of glycosylated sAA.

BIOCHEMICAL STUDIES ON α-AMYLASE INHIBITOR EXTRACTED FROM WHITE KIDNEY BEAN (Phaseolus vulgaris)

Crude extract of white kidney beans (Phaseolus vulgaris) showed inhibitory activity against porcine pancreatic α-amylase and human salivary α-amylase. Alpha amylase inhibitors are substances which alter the catalytic action of alpha amylase on starch and consequently slow down or stop the breakdown of starch. The obtained extract was examined qualitatively for phytochemical constituents and total protein content was determined by Lowry method. The crude extract was also studied for α-amylase inhibition activity which showed a linear relationship between the percentage of inhibition and inhibitor concentrations. Optimum temperature was 37oC, optimum periods for preincubation and incubation were 15 and 60 min. Nearly 90 % of inhibition was occurred after 60 min from the beginning of incubation. Kidney bean crude extract inhibits porcine pancreatic α-amylase and human saliva α-amylase in a non-competitive manner.

Characteristic hydrolyzing of megalosaccharide by human salivary α-amylase and small intestinal enzymes, and its bioavailability in healthy subjects

The digestibility of Megalosaccharide® (newly developed carbohydrate comprising α-1,4-glucosaccharide) was investigated in vitro and in vivo. Isomaltosyl-megalosaccharide® (IMS) and nigerosyl-megalosaccharide® (NMS) contain 20% and 50% of the megalosaccharide fraction (degree of polymerization (DP) 10–35), respectively. IMS was hydrolyzed readily by α-amylase to oligosaccharides (DP ≤ 7), and a small amount of glucose was produced from oligosaccharides by small intestinal enzymes (SIEs). NMS was partially hydrolyzed by α-amylase to oligosaccharides, and a small amount of glucose produced by SIEs. When IMS and NMS were treated by SIEs after treatment with human saliva α-amylase for a few minutes, IMS and NMS were hydrolyzed readily to glucose. Plasma levels of glucose and insulin upon ingestion of 50 g of IMS or NMS were elevated the same as those for 50 g of glucose, and breath hydrogen was not excreted. These results suggest that IMS and NMS are digestible carbohydrates.

AnIn VitroandIn VivoStudy of the α-Amylase Activity of Phaseolamin

We evaluated the polypeptide profiles, inhibition of human salivary α-amylase activity, and hemagglutination properties of a commercial phaseolamin sample. We also performed an in vivo assay to investigate the effects of a commercial phaseolamin treatment (100, 500, or 1500 mg/kg) over 20 days on the glycemia, body weight, and serum biochemical parameters (total cholesterol, triglycerides, alanine aminotransferase, and aspartate aminotransferase) of nondiabetic and streptozotocin-induced diabetic rats. The in vitro evaluation showed defined protein profiles, low hemagglutination activity, and high α-amylase inhibition. None of the experimental groups treated with phaseolamin or acarbose showed decreases in body weight. Our data demonstrate that phaseolamin inhibits amylase activity in vitro, reduces blood glucose levels, decreases or attenuates some of the renal and hepatic effects of diabetes in streptozotocin-induced rats, and could therefore have therapeutic potential in the treatment or prevention of the complications of diabetes.

False‐Positive Results with Amylase Testing of Citrus Fruits

In a case of robbery in which the criminals passed through the garden adorned with calamondin trees (Citrus madurensis), the investigators found in the grass six calamondin fruits, some undamaged, while others apparently bitten. The fruits were collected and sent to the laboratory for DNA analysis to verify the presence of saliva and robbers' DNA profile. A specific immunochromatographic strip test for saliva confirmed the presence of human salivary α-amylase, but similar positive results were also observed for intact calamondin and other citrus fruits. Further analysis with a specific automated amylase test confirmed the absence of amylase activity. DNA quantification and typing using a specific forensic kit revealed no human DNA presence in any fruits. This case report demonstrates for the first time the occurrence of false positives when human saliva is sought on citrus fruits.

Inhibition of salivary and pancreatic α-amylases by a pinhão coat (Araucaria angustifolia) extract rich in condensed tannin

The purpose of the present work was to investigate the possible inhibitory effect of a pinhão coat extract rich in condensed tannin on the activity of α-amylases (human salivary and porcine pancreatic). Experiments with the classic α-amylase inhibitor acarbose and a condensed tannin from Acacia mearnsii were done for comparative purposes. Fourier transform-infrared spectroscopy analysis of the pinhão coat tannin revealed a higher proportion of procyanidins to prodelphinidins when compared to the A. mearnsii tannin. The pinhão coat extract rich in condensed tannin was an effective inhibitor of both human salivary and porcine pancreatic α-amylase. Inhibition was of the mixed S-parabolic I-parabolic type. For the human salivary α-amylase the inhibition constants were 56.88±5.74 and 103.27±11.85μg/L; for the porcine pancreatic α-amylase the inhibition constants were smaller, namely, 20.25±1.97 and 46.79±4.57μg/L. The decreasing potency sequence was: acarbose>pinhão coat extract rich in tannin>A. mearnsii tannin. Similarly to acarbose and the A. mearnsii tannin, the pinhão coat extract was also effective in diminishing the post-prandial glycemic levels in rats after starch administration. The inhibitory properties of the pinhão coat extract indicate that it can be used to suppress postprandial hyperglycemia in diabetic patients.

Pub: Probing the Interaction of Human Salivary Alpha-Amylase and Amylase Binding Protein A(AbpA) of Streptococcus gordonii

Amylase binding protein A (AbpA) of Streptococcus gordonii serves as a major receptor for human salivary α-amylase (HSAmy), the predominant enzyme in human salivary secretions, to bind to the bacterial cell surface. On enamel surfaces, the binding of AbpA to HSAmy renders S. gordonii act as a scaffold for other oral bacteria to attach to the acquired enamel pellicle leading to complex bacterial communities and invasion of host tissues. While the role of AbpA in adhesion, starch metabolism and biofilm formation in influencing the ecology of the oral biofilms has been established, the structure function relationships of AbpA are yet to be defined. Since distally located aromatic residues of HSAmy are involved in the interaction with AbpA, we hypothesized that AbpA might use separate structural regions to bind to HSAmy. To test this, several deletion mutants of AbpA were constructed and studied to correlate the effect of deletions in binding to HSAmy in the following: 1) their secondary structural features through circular dichroism studies; 2) their ability to alter the capacity of HSAmy to hydrolyze starch and several oligosaccharides after complex formation and 3) their binding to HSAmy using surface plasmon resonance spectroscopy. Our results showed that a) AbpA does not bind at the active site of salivary α-amylase; b) both the N-terminal region (24-56 residues) and a central region (residues 124-165) are required for binding to HSAmy; and c) the C-terminal end residues (166- 195) are not necessary for binding. These results clearly show that AbpA binding to HSAmy encompasses distinct and distal regions of the structure.