Sucrose phosphorolysis

Phosphorylases have been described for the polysaccharides, glycogen and amylose, and for sucrose. Phosphorylases from both muscle and plants are able to cleave the 1, 4 -qj linkages of glycogen and starch to yield glucose-1-phosphate. Sucrose phosphorylase is a separate enzyme obtained from bacteria which produces glucose-l-phosphate and fructose from sucrose. Phosphorolysis has also been involved in the cleavage of the pentosidic... 

The first group is comprised that of compounds which potentially could be degraded to form G-l-P by phosphorolysis by beta-linkage specific enzymes. They include IPTGlu, cellobiose, sophorose, salicin, and sucrose. Addition of these compounds, or exogenous G-l-P, to Solka Floe fermentations improved maximum cellulase yields from 171 to 309%, and the time period for enzyme synthesis was reduced from 95 to 59% compared with using Solka Floe only. 

Arsenate similarly replaces phosphate in various phosphorolysis reactions, so that sucrose phosphorylase catalyzes the hydrolysis of sucrose in its presence (23), potato phosphorylase can hydrolyze amylose and amylopectin (24), nucleoside phosphorylase can hydrolyze inosine... 

One possible way to solve this problem is to combine another enzyme, like SP, which produces a-GlP for GP. Waldmann and colleagues reported the combined use of SP and GP for the production of amylose from sucrose (1986). In this system, SP catalyzes the phosphorolysis of sucrose to produce a-GlP and fructose, and the a-GlP is next used as a substrate of GP to produce amylose. An interesting feature of this SP-GP system is that Pi produced in the second GP reaction is used as a substrate for the first SP reaction. The cooperative action by the two phosphorylases proceeds continuously with a constant Pi concentration, without any inhibition caused by an accumulation of Pi. Based on this SP-GP system, we have now established the process to manufacture essentially linear amylose with controlled molecular size, by using thermostable variants of SP and GP (Yanase et al., 2007 Ohdan et al., 2007). 

We next tried to provide a-GlP, not from sucrose, but from cellobiose by using CBP. When CBP from Clostridium thermocellum (Kim et al., 2002) and GP were incubated with cellobiose in the presence of Pi and maltooligosac-chride primer, linear a-1,4 glucan was synthesized wth a yield (38.6 %) that was much lower than in the SP-GP method (Ohdan et al., 2007). To improve the yield of amylose, mutarotase and glucose oxidase were added to the initial reaction mixture with the expectation that they would remove the glucose derived from the CBP reaction and consequently shift the equilibrium state to phosphorolysis. The yield of amylose was increased to 64.8% (Ohdan et al., 2007). 

E.C.2.4.1.5, and 2.4.1.140) that catalyze the conversion of sucrose for the synthesis of high-molecular weight glucans, and sucrose phosphorylases (E.C.2.4.1.7) which catalyze the phosphorolysis of sucrose to produce glucose-1-phosphate. They both utilize sucrose as the sole source of energy to synthesize their products. 

Sucrose phosphorylase is a bacterial enzyme that catalyzes the phosphorolysis of sucrose to yield glucose-1-phosphate and fructose. 

The equilibrium constant for the phosphorolysis of sucrose, expressed by the mass law equation ... 

The reaction is essentially an exchange of hypoxanthine for phosphate, and is analogous to the phosphorolysis of glycogen and sucrose. For this reason, the enzyme has been termed nucleoside phosphorylase. It can also catalyze an exchange between ribose-l-phosphate and inorganic phosphate. This was shown by incubating ribose-l-phosphate with P in the presence of the enzyme and subsequently isolating radioactive ribose-l-phosphate. With arsenate, an irreversible arsenolysis of the nucleoside results. 

In the case of polysaccharides and sucrose both phosphorolytic and hydrolytic types of cleavage have been recognized. It appeared for a time as if phosphorolysis were the only mechanism for nucleoside splitting. Now, however, two other reactions involving cleavage at the N-glycosidic linkage are known. They are (1) hydrolysis and (2) base transfer reactions. 

It will be observed that in this, as well as in the phosphorolysis reaction, the enzyme acts as glucose donor and glucose acceptor to its substrates, and is able to catalyze the exchange of an ester bond for a glyco-sidic bond. The role of sucrose phosphorylase in the reversible phosphorolysis of sucrose can thus be considered as a summation of the two reactions. 

The same can be observed in the phosphorolysis of sucrose with sucrose phosphorylase ... 

The observed single inversion in the phosphorolysis of maltose may be explained on the basis of a three-component system in which the phosphate transfer occurs between the substrates rather than between the enzyme and each substrate separately. The occurrence of the inversion would indicate that the carbon oxygen bond of the phosphate ester is broken, as has been shown in the case of sucrose phosphorylase. ... 

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