Amylases isoamylases

The linkages of amylopectin and glycogen provide the cell with a glucose polysaccharide that upon action by degradative enzymes, such as amylases, isoamylases, debranching enzymes, or phosphorylases are easily converted into glucose and or a-Glc-1-P. 

Fig. 11.—Successive Actions of Phosphorylase, beta-Amylase, Isoamylase, and befa-Amylase on the Meyer Model of Amylopectin and Glycogen. [The symbolism is basically that of Fig. 9, modified to show the action of the various enzymes as follows - - - removed by pho horylase and heto>amylase , branch points hydrolyzed by isoamylase and-, immune to beta amy]ase after isoamylase action.]...

Fig. 12.—(a) Structure Proposed for Glycogen and Amylopectin by Whelan and Coworkers. [The symbols are as given in Fig. 9.] (b) Successive Actions of Phosphorylase, heia-Amylase, Isoamylase, and heta-Amylase on the Whelan Model. 

W5. Warshaw, A. L., and Lee, K. H., Aging changes of pancreatic isoamylases and the appearance of old amylase in the serum of patients with pancreatic pseudocysts. Gastroenterology 79, 1246-1251 (1980). 

Primary, secondary and tertiary structures of amylolytic enzymes from a wide variety of sources and functions (the a-amylases, bacterial cyclomaltodextrin glucanosyltrans-ferases, isoamylases and starch-branching enzymes) have been found to be closely related, and have been placed into the so-called structural a-amylase family.176,177 These enzymes have been studied with regard to the number, structure, organization and function of domains.178... 

The major enzymes that have been used for studying structures of starch polymers and fragments from them are the endo-acting a-amylases, the exo-acting glucoamylase and (3-amylases, and the debranching enzymes, isoamylases and pullulanases. These enzymes have varied and diverse specificities that have been extensively studied (see previous sections). 

By use of a debranching enzyme, isoamylase or pullulanase, the a-D-(l — 6)-linkages in amylopectin are broken, thus opening up to beta-amylase action those parts of the amylopectin molecule that are otherwise resistant.14 In this way, syrups of very high maltose content can be made.19... 

Whitten RO, Chandler WL, Thomas MGE, Clayson KJ, Fine JS. Survey of a-amylase activity and isoamylases in autopsy tissue. Clin Chem 1988 34 1552-5,... 

Murtaugh, R. J., and R. M. Jacobs. 1985. Serum amylase and isoamylases and their organs in healthy dogs and dogs with experimentally induced acute pancreatitis. American Journal of Veterinary Research 46 742-747. 

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