Maltose formation

Maltose formation by the maltose phosphorylase reversible reaction. 

Cleavage of maltose by maltase leads to a fraction of 3-D-glucose which is considerably lower than that present in equilibrium (63%). Consequently, the sensitivity of a maltase-GOD sequence electrode is lower for maltose than for glucose. Such a sensor is being used in a commercial analyzer for a-amylase assay in serum (Osawa et al., 1981), indicating the rate of maltose formation. 

Figure 5. The kinetics of product (maltose) formation from starch hydrolysis catalysed by immobilised a-amylase in a a-amylase/PHEMA complex (weight ratio T/M - 1/2). Production conditions of the complex 60 C, phosphate buffer (0.02 M, pH = 6.9), reaction time 20 min.

The approximate times of osazone formation in minutes are given in Table 111,139. The product from mannose is the simple hydrazone and is practically white. Arabinose osazone separates first as an oil, whilst that from galactose is highly crystalline. Lactose and maltose give no precipitate from hot solution. 

Maltose phosphorylase proceeds via a single-displacement reaction that necessarily requires the formation of a ternary maltose E Pi (or glucose E glucose-l-phosphate) complex for any reaction to occur. Exchange reactions are a characteristic of enzymes that obey double-displacement mechanisms at some point in their catalysis. 

Harrison, Tarr and Hibbert96 investigated the production of levan from sucrose by the action of Bacillus subtilis Cohn and B. mesentericus Trevisan. Nutrient solutions containing 10% carbohydrate, 0.1% peptone, 0.2% disodium hydrogen phosphate and 0.5% potassium chloride were incubated at 37° for six days. Levan formation occurred only with sucrose and raffinose, and not with melezitose, lactose, maltose, D-xylose, D-glucose or D-fructose. It was therefore suggested that only those carbohydrates with a terminal D-fructofuranose residue were satisfactory substrates for levan formation. 

Addition of an aqueous solution of PEG to a saturated aqueous solution of a-CD at room temperature did not lead to complex formation unless the average molecular weight of PEG exceeded 200 [46]. Moreover, carbohydrate polymers such as dextran and pullulan failed to precipitate complexes with PEG, and the same was true for amylose, glucose, methyl glucose, maltose, maltotriose, cyclodextrin derivatives, such as glucosyl-a-CD and maltosyl-a-CD, and water-soluble polymers of a-CD crosslinked by epichlorohydrin. These facts suggested to Harada et al. the direction for further research. 

Malonate complexes, osmium, 37 286 Maltose phosphorylase, arsenate and, 44 194 compound I formation, 43 99 exogenous reduction of intermediates, 43 116-119... 

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