Maltotetraose substrate

Flypothetical interactions of a five-subsite enzyme with a maltotetraose substrate shown initially with a terminally radiolabeled (filled circles) nonreducing end. The vertical arrow indicates the glycosyl bond cleavage region the roman numerals indicate the subsites, and the 4 indicates the chain length. Only three binding interactions lead to hydrolysis IV,4 V,4 and Vl,4, and their different associated rate constants emphasize that the rates of hydrolysis need not be identical. From Allen and Thoma with permission of the Biochemical Society (London). 

Maltotetraose was a very poor substrate for the enzyme and the products were observed only after long-term reaction. (Reprinted with permission from Ref. 13. Copyright 1990 Academic Press, Inc.)... 

For a glucan to be a substrate for starch phosphorylase, it must be longer than maltotetraose. Shorter oligosaccharides, however, can be used by glucosyltransferases such as D-enzyme (EC 2.4.1.25) in the reaction... 

Figure 9.72 Chromatograms of the action patterns of maltoheptaose after the indicated periods of incubation with a-amylase and a-glucosidase. Peaks 1, glucose 2, maltose 3, maltotriose 4, maltotetraose 5, maltopentaose (x) compound A 6, maltohexaose 7, maltoheptaose. (A) Pure maltoheptaose used for the assay. (B) Blank sample before the addition of substrate. (C-H) Chromatograms after 1, 5, 10,15, 20, and 30 minutes, respectively, of incubation. Chromatographic conditions column, 10 jum Nucleosil SA (250 mm X 4 mm) solvent, acetonitrile-water (72.527.5) flow rate, 0.7 mL/min temperature, 27°C detection, differential refractometer, full scale = 2 X 10-6 refractive index units. (From Haegel et aL, 1981.)...

Furthermore, a-D-mannose-1-phosphate represents a substrate for the enzyme, and the a-mannosyl-maltotetraose is obtained. Supplementary to this result, the a-phosphate of uronic acid was tested, but no enzymatic elongation... 

The molecular mechanism of the substrate recognition and phosphorolysis of phosphorylase was presented.111 The ternary complex of malto-oligosaccha-ride phosphorylase, 4-5-a-D-glucopyranosyl-4-thio-maltotetraose, and phosphate shows that the phosphate group attacked the glycosidic linkage and promoted the phosphorolysis. 

Maltotetraose has also been used as a substrate in the following reaction scheme ... 

Synthesis by P-enzyme occurs by multi-chain action, that is, all the acceptor substrate molecules are increased at approximately the same rate. With maltotetraose or maltohexaose as acceptor, the iodine-pro-duced stain of the products changes from red (degree of polymerization, DP,... 

According to these data it can be established that maltose, maltotriose and maltotetraose are not good substrates of Aspergillus oryzae a-amylase whereas maltopentaose and maltohexaose act as good substrates of the enzyme hexaose/sthe better one. 

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