Enzymes glucosidase reaction

Figure 47-9. Schematic pathway of oligosaccharide processing. The reactions are catalyzed by the following enzymes , oligosaccharideiprotein transferase , a-glucosidase I ...

Enzyme activity (urease, amidase, dehydrogenase, pl-glucosidase, phosphatase, arylsulfatase, fluorescein diacetate hydrolysis) Laboratory incubation Indicates potential microbial activity and nutrient cycling reactions determined in nonstandard laboratory with specialized equipment highly spatially and temporally variable dependent upon organic inputs Dick et al. (1996) Parham et aL (2002)... 

One problem identified at the outset was that MPEG or a monosaccharide DOX-MPEG as acceptors had to be presented to a glucosidase in a concentration, which renders the solution quite viscous at 37°C, and consequently the reaction becomes very slow.47 Below this acceptor concentration threshold, reaction yields were very low. Enzymes from thermophilic bacteria working at higher temperatures... 

For example ca. 4 pmole of parathion can be metabolized (to a 4-nitrcphenol hydrolysis prodix t) in one hour by a suspension of 10 cells (Shen and Dcwd unpublished data). Dechlorination of 1-chloro 2 4-dinitrdDenzene, by a cell-free extract (1000 g supernatant) occurred at a rate of 20 nmole/min/mg protein (Shen and DcMd unpublished data). This dechlorination reaction appears to be performed by a glutathione transferase-like enzyme, since the reaction is glutathione dependent. Both a-glucosidase and 3-glucosidase activity have also been detected (Shen and Dcwd uipublished data). 

More specific hydrolysis may be achieved by the use of enzymes. Thus, the enzyme a-amylase in saliva and in the gut is able to catalyse hydrolysis of al 4 bonds throughout the starch molecule to give mainly maltose, with some glucose and maltotriose, the trisaccharide of glucose. Amylose is hydrolysed completely by this enzyme, but the al 6 bonds of amylopectin are not affected. Another digestive enzyme, a-l,6-glucosidase, is required for this reaction. Finally, pancreatic maltase completes the hydrolysis by hydrolysing maltose and maltotriose. 

Incorporation of [14C]-glucose into glycogen by the reverse reaction of the hydrolase amylo-l,6-glucosidase. Measurement of the incorporated radioactivity in the precipitated glycogen [20, 39]. This assay can only test the enzymes function of the hydrolysis of the 1-6 bond (see section 4.6.16.1). 

---