Phosphorylases

Phosphorylase is a family of allosteric enzymes that catalyze the production of glucose-1-phosphate from a polyglucose such as glycogen, starch or maltodextrin. Phosphorylase is also a common name used for glycogen phosphorylase in honor of Earl W. Sutherland Jr. who in the late 1930's discovered the first phosphorylase.

Function
More generally, phosphorylases are enzymes that catalyze the addition of a phosphate group from an inorganic phosphate (phosphate+hydrogen) to an acceptor. Do not confuse this enzyme with a phosphatase or a kinase. A phosphatase removes a phosphate group from a donor, while a kinase transfers a phosphate group from a donor (usually ATP) to an acceptor.

Types
The phosphorylases are named by prepending the name of the substrate, e.g. glycogen phosphorylase, starch phosphorylase, maltodextrin phosphorylase.

All known phosphorylases share catalytic and structural properties.

Activation
Phosphorylase a is the active form of glycogen phosphorylase that is derived from the phosphorylation of the inactive form, phosphorylase b.

Pathology
Some disorders are related to phosphorylases:


 * Glycogen storage disease type V - muscle glycogen
 * Glycogen storage disease type VI - liver glycogen