Human salivary a-amylase

A. oryzae a-amylase has about the same degree of multiple attack as human salivary a-amylase, i.e. an average of three hydrolytic cleavages per chain encounter. A. oryzae a-amylase is the only common a-amylase known to hydrolyze the cyclic a-(l- 4)-l inked maltodextrins to any extent.25,26 A kinetic analysis revealed that the catalytic constant, k2, increased significantly from 3.3 to 270 to 3270min-1 for cyclomaltohexaose, cyclomaltoheptaose and cyclomalto-octaose, respectively, while the Km was 4.7 M, 10.2 M and 2.4 M, respectively.26... 

Uchida et al.220b reported the synthesis of 6m-deoxy maltodextrins by B. macerans CGTase transglycosylation reactions between mono-6-O-p-toluene sulfonyl cyclomal-tohexaose and maltose. The best inhibitors for human salivary a-amylase and human pancreatic a-amylase were 6m-deoxy maltotetraose and 6m-deoxy maltopentaose. 

Kj values, however, were in the nanomolar range, with the Kj for the maltohexaosyl acarbose, 33 nM for A. oryzae a-amylase, 37 nM for B. amyloliquefaciens a-amylase, 14nM for human salivary a-amylase and 7.0nM for porcine pancreatic a-amylase. These inhibition constants represented relative inhibitory potency over acarbose of 8200-, 351 -, 90- and 114-times, respectively for the four a-amylases.220d... 

In a similar use of a-amylase, Parrish and Whelan249 treated potato starch with crystalline human salivary a-amylase and obtained a phosphorylated maltotetraose that had previously been reported by Postemak250 and that was the smallest phospho-dextrin formed. They determined its structure to be 63-phosphomaItotetraose, similar in structure to the smallest a-limit dextrin, 63-a- D-glucopyranosylmaltotriose, formed by this enzyme and porcine pancreatic a-amylase. 

Figure 7. High performance liquid chromatography of reaction product of elsinan with human salivary a-amylase.

Figure 8. Action pattern of human salivary a-amylase on elsinan ( ) represents the sites cleaved by the enzyme G, a-D-glucopyranosyl residue...

Ion-exchange chromatography separated four inhibitors of a-amylase from an alcoholic extract of wheat. After extensive purification, one of them (mol. wt. 2.1 X 10" ) was 100 times more reactive towards human salivary a-amylase than towards human pancreatic a-amylase. 

A method described for the determination of (human) salivary a-amylase is based on the hydrolysis of 4-nitrophenyl a-maltoside to give 4-nitrophenol. Precision estimates for the method were considered in detail. The production of oligosaccharide substrates for oc-amylase and the actions of the human parotid and human and porcine pancreatic a-amylases upon them were compared. ... 

The effects of various ions in conjunction with tris or amino-acids upon the activity of human salivary a-amylase have been investigated. Though it has been claimed previously that Na+ is an activator of a-amylase, the current study reconfirmed that sodium ion does not activate the human enzyme. A continuous flow method for the estimation of serum a-amylase activity uses amylopectin dyed with DyAmyl-L as substrate. ... 

Several enzyme inhibitors are useful for the control of carbohydrate-dependent diseases, such as diabetes. One of these is acarbose, a pseudopolysaccharide produced by an Actinoplanes strain. Acarbose inhibits intestinal a-glucosidase thus reducing the conversion of starch into glucose (Truscheit et al. 1981). Other enzymes, the protein a-amylases from plants, are effective inhibitors of human a-amylases, in contrast with several a-amylases isolated from streptomycetes (e.g., pami and Haim II) which are active in various animals but not in humans. However, a new polypeptide, Al-409, produced by Streptomyces chartreusis was recently shown to be active on human salivary a-amylase, opening the way to further studies (Imada 2004). 

Crystalline human salivary a-amylase produced 6 -phosphomaltotetraose from potato amylopectin, demonstrating that the covalently linked phosphate in potato starch was attached to the C-6 hydroxyl group by a phosphoester linkage in amylopectin [23]. 

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