Glycosylated salivary alpha-amylases are capable of maltotriose hydrolysis and glucose formation

Murine Salivary Amylase Protects Against Streptococcus mutans-Induced Caries

Saliva protects dental surfaces against cavities (i. e., dental caries), a highly prevalent infectious disease frequently associated with acidogenic Streptococcus mutans. Substantial in vitro evidence supports amylase, a major constituent of saliva, as either protective against caries or supporting caries. We therefore produced mice with targeted deletion of salivary amylase (Amy1) and determined the impact on caries in mice challenged with S. mutans and fed a diet rich in sucrose to promote caries. Total smooth surface and sulcal caries were 2.35-fold and 1.79-fold greater in knockout mice, respectively, plus caries severities were twofold or greater on sulcal and smooth surfaces. In in vitro experiments with samples of whole stimulated saliva, amylase expression did not affect the adherence of S. mutans to saliva-coated hydroxyapatite and slightly increased its aggregation in solution (i.e., oral clearance). Conversely, S. mutans in biofilms formed in saliva with 1% glucose displayed no differences when cultured on polystyrene, but on hydroxyapatite was 40% less with amylase expression, suggesting that recognition by S. mutans of amylase bound to hydroxyapatite suppresses growth. However, this effect was overshadowed in vivo, as the recoveries of S. mutans from dental plaque were similar between both groups of mice, suggesting that amylase expression helps decrease plaque acids from S. mutans that dissolve dental enamel. With amylase deletion, commensal streptococcal species increased from ~75 to 90% of the total oral microbiota, suggesting that amylase may promote higher plaque pH by supporting colonization by base-producing oral commensals. Importantly, collective results indicate that amylase may serve as a biomarker of caries risk.

Amylases: Biofilm Inducer or Biofilm Inhibitor?

Biofilm is a syntrophic association of sessile groups of microbial cells that adhere to biotic and abiotic surfaces with the help of pili and extracellular polymeric substances (EPS). EPSs also prevent penetration of antimicrobials/antibiotics into the sessile groups of cells. Hence, methods and agents to avoid or remove biofilms are urgently needed. Enzymes play important roles in the removal of biofilm in natural environments and may be promising agents for this purpose. As the major component of the EPS is polysaccharide, amylase has inhibited EPS by preventing the adherence of the microbial cells, thus making amylase a suitable antimicrobial agent. On the other hand, salivary amylase binds to amylase-binding protein of plaque-forming Streptococci and initiates the formation of biofilm. This review investigates the contradictory actions and microbe-associated genes of amylases, with emphasis on their structural and functional characteristics.

Changes Occurring on the Activity of Salivary Alpha-Amylase Proteoforms in Two Naturalistic Situations Using a Spectrophotometric Assay

Simple Summary

Salivary alpha-amylase (sAA) is considered a biomarker of acute stress since this enzyme is released in saliva after autonomic nervous system activation, in response to psychological or physical stress situations. This enzyme has different isoforms that could be differentially expressed depending on the stressful situation. The aims of the present research were (1) to develop and validate an easy and fast method to estimate the activity of the major sAA proteoforms (both non-glycosylated and glycosylated proteoforms) in saliva samples, and (2) to evaluate the possible changes occurring in the activity of both proteoforms when measured by this method in two different stress models (physical effort and psychological challenge). This new method was precise and, when applied to the different stress models, allowed to detect changes of different magnitudes in both proteoforms. Therefore, this research opens a new field for the evaluation of isoforms of sAA as potential biomarkers of stress.

Abstract

This study aimed to evaluate the changes in the activity of total salivary alpha-amylase (TsAA) and both the non-glycosylated and glycosylated salivary alpha-amylase proteoforms (NGsAA and GsAA, respectively) in physical and psychological stress models, estimated using a simple and easily set-up method. The method used was a spectrophotometric assay with 2-chloro-4-nitrophenyl-α-D-maltotriose (CNPG3) as a substrate, incubated with Concanavalin A (ConA) to remove most of the glycosylated protein from the sample. This method allowed the measurement of TsAA and estimation of NGsAA and GsAA activities with imprecision lower than 10%. When this method was applied to two different stress models, differences in the responses of the proteoforms were observed, with the NGsAA activity showing changes of higher magnitude after stress induction than the GsAA activity, and the highest correlation with the State–Trait Anxiety Inventory Scale in the Trier Social Stress Test (TSST). In conclusion, the activity of the two main sAA proteoforms can be easily estimated in saliva, and their measurement can provide additional information on TsAA activity in physical or psychological stress situations.

The rise in glucose concentration in saliva samples mixed with test foods monitored using a glucometer: An observational pilot study

OBJECTIVES

The aim of this study was to quantify the changes in glucose concentration in unstimulated saliva samples mixed with finely crushed salted sticks or oat meal using a readily available portable glucometer.

METHODS

Glucose measurements were taken every 10 min during a 1 h monitoring period, for a total of 14 saliva samples mixed with test foods. Salivary amylase activity was measured immediately after saliva collection (T0) and after 1h (T60). Level of salivary amylase activity was correlated with an increase in glucose concentration.

RESULTS

We observed significant differences in the rate of increase in glucose concentration between the two different test foods, with salted sticks leading to greater increase in glucose concentration. No significant association was found between salivary amylase activity and the rate of increase in glucose concentration. The mean level of amylase activity at T60 was higher than that at T0, but this difference was not significant.

CONCLUSIONS

This pilot study presents glucose release rate characteristics from specific food particles mixed with saliva in vitro suggesting that the same process takes place in the oral cavity. However, the characteristics of this process when occurring in the mouth would expectedly be modified by different factors such as rinsing effect of salivary flow, oral temperature, etc. Prolonged release of low molecular carbohydrates such as maltose and glucose from food particles can be considered cariogenic and therefore unfavorable for individuals with other risk factors contributing to the development of dental caries.

Saliva: a Dynamic Proteome

The proteome of whole saliva, in contrast to that of serum, is highly susceptible to a variety of physiological and biochemical processes. First, salivary protein secretion is under neurologic control, with protein output being dependent on the stimulus. Second, extensive salivary protein modifications occur in the oral environment, where a plethora of host- and bacteria-derived enzymes act on proteins emanating from the glandular ducts. Salivary protein biosynthesis starts with the transcription and translation of salivary protein genes in the glands, followed by post-translational processing involving protein glycosylation, phosphorylation, and proteolysis. This gives rise to salivary proteins occurring in families, consisting of structurally closely related family members. Once glandular secretions enter the non-sterile oral environment, proteins are subjected to additional and continuous protein modifications, leading to extensive proteolytic cleavage, partial deglycosylation, and protein-protein complex formation. All these protein modifications occur in a dynamic environment dictated by the continuous supply of newly synthesized proteins and removal by swallowing. Understanding the proteome of whole saliva in an environment of continuous turnover will be a prerequisite to gain insight into the physiological and pathological processes relevant to oral health, and be crucial for the identification of meaningful biomarkers for oral disease.

Inhibition of salivary amylase by black tea in high-caries and low-caries index children: A comparative in vivo study

Introduction:

Dental caries is a universal disease. Dietary modification is important in reducing the occurrence of dental caries. Tea which is so frequently consumed with cariogenic starch rich food is proposed to have anticariogenic potential. The various mechanism has been proposed for same and one being inhibition of salivary amylase activity.

Aim:

To determine the effect of 1.5% black tea decoction on salivary amylase activity in children with high caries and no caries.

Materials and Methods:

A total of 30 children in the age group of 12–15 years were selected for the study. They were further grouped based on their decayed missing filled surface (DMFS) score into high-caries group (DMFS above 10) and no-caries group (DMFS = 0). After 2 h of fasting, subjects consumed two salted crackers for 60 s following which they rinsed with water and then with black tea decoction (1.5%) the very next day. Retained food particles were recovered salivary amylase activity was noted as maltose to sucrose ratio via chromatography.

Results:

The average ratio of maltose to sucrose ratio percentage reduction in high-caries group was 43.63% and 41.17% in no caries group which was highly significant (P < 0.005) while the intergroup comparison was found statistically insignificant.

Conclusions:

Tea decoction has inhibitory effect on salivary amylase activity thus dental caries. The effect was statistically insignificant in children with high- and no-caries index.

Influences of AMY1 gene copy number and protein expression on salivary alpha-amylase activity before and after citric acid stimulation in splenic asthenia children

OBJECTIVE

To compare the correlations between salivary alpha-amylase (sAA) activity and amylase, alpha 1 (salivary) gene (AMYl) copy number or its gene expression between splenic asthenia and healthy children, and investigate the reasons of attenuated sAA activity ratio before and after citric acid stimulation in splenic asthenia children.

METHODS

Saliva samples from 20 splenic asthenia children and 29 healthy children were collected before and after citric acid stimulation. AMYl copy number, sAA activity, and total sAA and glycosylated sAA contents were determined, and their correlations were analyzed.

RESULTS

Although splenic asthenia and healthy children had no differences in AMY1 copy number, splenic asthenia children had positive correlations between AMY1 copy number and sAA activity before or after citric acid stimulation. Splenic asthenia children had a higher sAA glycosylated proportion ratio and glycosylated sAA content ratio, while their total sAA content ratio and sAA activity ratio were lower compared with healthy children. The glycosylated sAA content ratio was higher than the total sAA content ratio in both groups. Splenic asthenia and healthy children had positive correlations between total sAA or glycosylated sAA content and sAA activity. However, the role played by glycosylated sAA content in sAA activity in healthy children increased after citric acid stimulation, while it decreased in splenic asthenia children.

CONCLUSION

Genetic factors like AMY1 copy number variations, and more importantly, sAA glycosylation abnormalities leading to attenuated sAA activity after citric acid stimulation, which were the main reasons of the attenuated sAA activity ratio in splenic asthenia children compared with healthy children.

Age Differences of Salivary Alpha-Amylase Levels of Basal and Acute Responses to Citric Acid Stimulation Between Chinese Children and Adults

It remains unclear how salivary alpha-amylase (sAA) levels respond to mechanical stimuli in different age groups. In addition, the role played by the sAA gene (AMY1) copy number and protein expression (glycosylated and non-glycosylated) in sAA activity has also been rarely reported. In this study, we analyzed saliva samples collected before and after citric acid stimulation from 47 child and 47 adult Chinese subjects. We observed that adults had higher sAA activity and sAA glycosylated levels (glycosylated sAA amount/total sAA amount) in basal and stimulated saliva when compared with children, while no differences were found in total or glycosylated sAA amount between them. Interestingly, adults showed attenuated sAA activity levels increase over those of children after stimulation. Correlation analysis showed that total sAA amount, glycosylated sAA amount, and AMY1 copy number × total sAA amount were all positively correlated with sAA activity before and after stimulation in both groups. Interestingly, correlation r between sAA levels (glycosylated sAA amount and total sAA amount) and sAA activity decreased after stimulation in children, while adults showed an increase in correlation r. In addition, the correlation r between AMY1 copy number × total sAA amount and sAA activity was higher than that between AMY1 copy number, total sAA amount, and sAA activity, respectively. Taken together, our results suggest that total sAA amount, glycosylated sAA amount, and the positive interaction between AMY1 copy number and total sAA amount are crucial in influencing sAA activity before and after stimulation in children and adults.

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.

Enzymatic conversions of starch

This article surveys methods for the enzymatic conversion of starch, involving hydrolases and nonhydrolyzing enzymes, as well as the role of microorganisms producing such enzymes. The sources of the most common enzymes are listed. These starch conversions are also presented in relation to their applications in the food, pharmaceutical, pulp, textile, and other branches of industry. Some sections are devoted to the fermentation of starch to ethanol and other products, and to the production of cyclodextrins, along with the properties of these products. Light is also shed on the enzymes involved in the digestion of starch in human and animal organisms. Enzymatic processes acting on starch are useful in structural studies of the substrates and in understanding the characteristics of digesting enzymes. One section presents the application of enzymes to these problems. The information that is included covers the period from the early 19th century up to 2009.

Taking the starch out of oral biofilm formation: molecular basis and functional significance of salivary α-amylase binding to oral streptococci

α-Amylase-binding streptococci (ABS) are a heterogeneous group of commensal oral bacterial species that comprise a significant proportion of dental plaque microfloras. Salivary α-amylase, one of the most abundant proteins in human saliva, binds to the surface of these bacteria via specific surface-exposed α-amylase-binding proteins. The functional significance of α-amylase-binding proteins in oral colonization by streptococci is important for understanding how salivary components influence oral biofilm formation by these important dental plaque species. This review summarizes the results of an extensive series of studies that have sought to define the molecular basis for α-amylase binding to the surface of the bacterium as well as the biological significance of this phenomenon in dental plaque biofilm formation.

Characterization of the human submandibular/sublingual saliva glycoproteome using lectin affinity chromatography coupled to multidimensional protein identification technology

In-depth analysis of the salivary proteome is fundamental to understanding the functions of salivary proteins in the oral cavity and to reveal disease biomarkers involved in different pathophysiological conditions, with the ultimate goal of improving patient diagnosis and prognosis. Submandibular and sublingual glands contribute saliva rich in glycoproteins to the total saliva output, making them valuable sources for glycoproteomic analysis. Lectin-affinity chromatography coupled to mass spectrometry-based shotgun proteomics was used to explore the submandibular/sublingual (SM/SL) saliva glycoproteome. A total of 262 N- and O-linked glycoproteins were identified by multidimensional protein identification technology (MudPIT). Only 38 were previously described in SM and SL salivas from the human salivary N-linked glycoproteome, while 224 were unique. Further comparison analysis with SM/SL saliva of the human saliva proteome, revealed 125 glycoproteins not formerly reported in this secretion. KEGG pathway analyses demonstrated that many of these glycoproteins are involved in processes such as complement and coagulation cascades, cell communication, glycosphingolipid biosynthesis neo-lactoseries, O-glycan biosynthesis, glycan structures-biosynthesis 2, starch and sucrose metabolism, peptidoglycan biosynthesis or others pathways. In summary, lectin-affinity chromatography coupled to MudPIT mass spectrometry identified many novel glycoproteins in SM/SL saliva. These new additions to the salivary proteome may prove to be a critical step for providing reliable biomarkers in the diagnosis of a myriad of oral and systemic diseases.

In depth study of a new highly efficient raw starch hydrolyzing α-amylase from Rhizomucor sp

A new α-amylase from Rhizomucor sp. (RA) was studied in detail due to its very efficient hydrolysis of raw starch granules at low temperature (32 °C). RA contains a starch binding domain (SBD) connected to the core amylase catalytic domain by a O-glycosylated linker. The mode of degradation of native maize starch granules and, in particular, the changes in the starch structure during the hydrolysis, was monitored for hydrolysis of raw starch at concentrations varying between 0.1 and 31%. RA was compared to porcine pancreatic α-amylase (PPA), which has been widely studied either on resistant starch or as a model enzyme in solid starch hydrolysis studies. RA is particularly efficient on native maize starch and release glucose only. The hydrolysis rate reaches 75% for a 31% starch solution and is complete at 0.1% starch concentration. The final hydrolysis rate was dependent on both starch concentration and enzyme amount applied. RA is also very efficient in hydrolyzing the crystalline domains in the maize starch granule. The major A-type crystalline structure is more rapidly degraded than amorphous domains in the first stages of hydrolysis. This is in agreement with the observed preferential hydrolysis of amylopectin, the starch constituent that forms the backbone of the crystalline part of the granule. Amylose-lipid complexes present in most cereal starches are degraded in a second stage, yielding amylose fragments that then reassociate into B-type crystalline structures, forming the final resistant fraction.

Glycoprofiling of the Human Salivary Proteome

Glycosylation is important for a number of biological processes and is perhaps the most abundant and complicated of the known post-translational modifications found on proteins. This work combines two-dimensional polyacrylamide gel electrophoresis (2-DE) and lectin blotting to map the salivary glycome, and mass spectrometry to identity the proteins that are associated with the glycome map. A panel of 15 lectins that recognize six sugar-specific categories was used to visualize the type and extent of glycosylation in saliva from two healthy male individuals. Lectin blots were compared to 2-D gels stained either with Sypro Ruby (protein stain) or Pro-Q Emerald 488 (glycoprotein stain). Each lectin shows a distinct pattern, even those belonging to the same sugar-specific category. In addition, the glycosylation profiles generated from the lectin blots show that most of the salivary proteins are glycosylated and that the pattern is more widespread than is demonstrated by the glycoprotein stained gel. Finally, the co-reactivity between two lectins was measured to determine the glycan structures that are most and least often associated with one another along with the population variation of the lectin reactivity for 66 individuals.

Expression of alpha-amylase isozymes in rat tissues

Gene expressions of alpha-amylase isozymes in rat tissues were analyzed by a reverse transcription-polymerase chain reaction (RT-PCR), followed by EcoRI digestion. This procedure is based on evidence that an RT-PCR product from mouse pancreas RNA is sensitive to EcoRI, but not the product from the salivary gland or liver RNAs. The method was applied to the analysis of alpha-amylase expression in rat liver after partial hepatectomy, in which a potent expression of pancreas type isozyme was observed. However, no expression of the pancreatic isozyme in the regenerating liver was found. We also analyzed the expression of alpha-amylase gene in several additional rat tissues. In intestine, stomach, testis and skeletal muscle, the corresponding PCR products were amplified, but few were detected in heart or spleen. Intestine and stomach expressed a pancreatic isozyme of alpha-amylase. Analyses of the alpha-amylase activity and protein indicated the presence of the enzyme in those tissues. Immunohistochemical analysis also indicated that the amylase proteins were specifically present in epithelial cells of rat intestinal mucosa. This is a convenient method for identification of alpha-amylase isozyme mRNA in rodent tissues.

A restriction endonuclease assay for expression of human alpha-amylase isozymes

BACKGROUND

The alpha-amylase isozymes can be detected separately by electrophoresis; however, sometimes the identification is difficult because of their microheterogeneity. In the present study, we tried to establish a convenient method for the detection of alpha-amylase isozyme expression.

METHODS

The procedure is based on three different restriction sites presented in those genes; a PstI site in both AMY 2A and 2B genes, a HaeII site in both AMY 1 and 2A genes, and a BamHI site in AMY 2B gene. After amplification from total tissue RNAs by RT-PCR with primers that were able to cover each exon, the products were cleaved with corresponding restriction endonucleases.

RESULTS

This method was applied to human samples from the parotid gland, liver (non-hepatoma), hepatoma and white blood cells (WBCs). The results indicated that the parotid gland and hepatoma (also liver) clearly expressed AMY 1 and AMY 2B genes, respectively. However, AMY 2B gene was also expressed apparently in WBCs, which produced salivary-type isozyme of the alpha-amylase, although the amylase protein was not able to identify for the hepatic isozyme.

CONCLUSIONS

The method presented here might be convenient and useful for the determination of alpha-amylase isozyme expression in humans.

alpha-Amylase expressed in human liver is encoded by the AMY-2B gene identified in tumorous tissues

BACKGROUND

An alpha-Amylase in human liver is detected with an anti-human salivary amylase antibody, but the enzyme activity is very low. We previously found that the rat liver contained an amylase which differed from the enzyme of mice. In this study, we characterized the human liver amylases biochemically and immunohistochermically.

METHODS AND RESULTS

Although the amylase activity of human liver was much lower than that of rat, protein moiety and sugar chains of the human amylase were identified as similar to the rat liver enzyme with an anti-human salivary amylase antibody and by concanavalin A (Con A) affinity chromatography. Liver amylases from human and rat were the same size, 50 kDa, on Western blot analysis and had the same isoelectric points. The cytoplasm of hepatocytes was moderately stained immunohistochemically with the anti-human salivary amylase antibody. Intrahepatic bile ducts were also stained weak-to-moderately. RT-PCR, with a specific primer for the consensus sequence of human amylases, amplified a single 474-bp product from the human liver total RNA. The PCR product was sequenced and referred to the homology. Thirteen bases in the 434-bp fragment of the human liver amylase differed from the corresponding region of the AMY-1 gene transcript and the deduced amino acid sequence differed at five residues. The human liver amylase cDNA sequence was identical to the corresponding cDNA of the AMY-2B, which was known to expressed in tumorous tissues. In situ hybridization revealed the expression of AMY-2B mRNA in non-tumorous human liver.

CONCLUSIONS

The present results suggest the possibility that a novel amylase detected in tumorous tissues and encoded by the AMY-2B gene is a liver-specific amylase expressed in the human liver.

Expression of alpha-amylase gene in rat liver: liver-specific amylase has a high affinity to glycogen

The reactivity of rat liver alpha-amylases with maltotriose (G3), maltopentose (G5) and glycogen has been investigated. Liver amylases were found to be glycosylated and to have a molecular mass of 50 kDa by Western blotting using an anti-human salivary amylase antibody. The glycosylated liver amylases were found to be capable of G3- and G5-hydrolysis and of glucose formation, as demonstrated by thin-layer chromatography. When the amylase preparation was exposed to different concentrations of glycogen and run on a cellulose acetate membrane, the mobilities of rat liver amylases significantly decreased with tailing directly from the point of origin. In contrast, rat salivary amylases were not so much. These results indicate that rat liver amylases have a strong affinity to glycogen. We confirmed the expression of liver-specific amylases in rat liver by reverse transcriptional-polymerase chain reaction (RT-PCR); PCR products showed one band of an expected size of 474 bp using primers tested in the present study. A partial nucleotide sequence was then determined. When compared with the gene of mouse liver amylase, the substitution of 26 bases out of 434 bases was elucidated. The present data demonstrate the presence of liver-specific amylases in rats.