Glucoamylase complex

Glucoamylase complex (EC 3.2.1.20) Glucoamylase-(maltase)-l and glucoamylase-(maltase)-2 (have hiiisimilaf... 

Individuals with genetic deficiencies of the sucrase-isomaltase complex show symptoms of sucrose intolerance but are able to digest normal amounts of starch in a meal, without problems. The maltase activity in the glucoamylase complex, and residual activity in the sucrase-isomaltase complex (which is normally present in excess of need) is apparently sufficient to digest normal amounts of dietary starch. 

Bonds (1) and (3) would first be hydrolyzed by glucoamylase. Bond (2) would require isomaltase. Bonds (4) and (5) could then be hydrolyzed by the sucrase-isomaltase complex, or by the glucoamylase complex, all of which can convert maltotriose and maltose to glucose. 

The isolation of a maltase-glucoamylase complex from rabbit intestines has been described. ... 

FIGURE 6.16 AFM images of glucoamylase-amylose complexes and binding models. 

Morris, V. J., Gunning, A. P., Faulds, C. B., Williamson, G., and Svensson, B. (2005). AFM images of complexes between amylose and Aspergillus niger glucoamylase mutants, native, and mutant starch binding domains A model for the action of glucoamylase. Starch-Starke 57,1-7. 

T. P. Frandsen, B. B. Stoffer, M. M. Palcic, S. Hof, and B. Svensson, Structure and energetics of the glucoamylase-isomaltose transition state complex probed by using modeling and deoxygenated substrates coupled with site-directed mutagenesis, J. Mol. Biol., 263 (1996) 79-89. 

E. M. S. Harris, A. E. Aleshin, L. M. Firsov, and R. B. Honzatko, Refined structure of the complex of 1-deoxynojirimycin with glucoamylase from Aspergillus awamori var. X100 to 2.4-A resolution, Biochemistry, 32 (1993) 1618—1626. 

L-arabinose, have also been reported to be in direct linkage with a protein. L-Arabinose may also be linked to L-serine and L-threonine in a hyaluronic acid-polypeptide complex from ox vitreous-humor.750 D-Mannose is reported to be glycosidically linked in a glucoamylase [(l->4)-a-D-glucan glucohydrolase, EC 3.2.1.3] from Aspergillus... 

This barrel can be compared with that of the 12-helix a, a barrel of a fungal glucoamylase whose structure is shown in Fig. 2-29. Numerous more complex folding patterns have been discovered. They have been classified by Jane Richardson.117 122 Many of the proteins described by these folding patterns can be grouped into families and "superfamilies."227 Chothia suggested that there may be about 1,000 families in nature 268 over 700, with over 360 distinct folds have been identified.2683... 

Digestion of dietary glycogen and starch in the human body begins with the salivary and pancreatic amylases, which cleave a-1,4 linkages at random. It continues with a glucoamylase found in the brush border membranes of the small intestine where it occurs as a complex with maltase.74 Carbohydrases are discussed in Chapter 12, Section B. 

Assay methods are available for most of the carbohydrates ranging from glycogen, starch, and cellulose to the monosaccharides and their monophosphates. Concentration determination of complex carbohydrates usually depends on their enzymatic hydrolysis to monosaccharides and determination of monosaccharide concentration via an enzymatic reaction. For example, starch is hydrolyzed to glucose by glucoamylase, and the... 

Randell, K D, Frandsen, T P, Stoffer, B, Johnson, M A, Svensson, B, Pinto, B M, Synthesis and glycosidase inhibitory activity of 5-thioglucopyranosylamines. Molecular modeling of complexes with glucoamylase, Carbohydr. Res., 321, 143-156, 1999. 

The dissociation constant for pullulan was larger than that for amy-lopectin due to the slow binding (kon) and the fast release (koff) of the enzyme (Table 3). The hydrolysis rate constant in the ES complex (kcat) of pullulan was ca. 30 times slower than that of amylopectin. This reflects the slow reaction of pullulan compared with amylopectin (curve e of Fig. 10a), due to the slow hydrolysis of a-1,6 linkages compared with a-1,4 hnkages catalyzed by glucoamylase [62,63]. 

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