Problem 14
Briefly predict the major consequences of each of the following mutations affecting glycogen utilization. (a) Loss of GTPase activity of the G-protein \(\alpha\) subunit. (b) Loss of phosphodiesterase activity.
Problem 15
Von Gierke disease is frequently the result of a defect in glucose 6 -phosphatase. Suggest another mutation in glucose metabolism that causes symptoms similar to those of von Gierke disease.
Problem 17
UDP-glucose is the activated form of glucose used in glycogen synthesis. However, we have already met other similar activated forms of carbohydrate in our consideration of metabolism. Where else have we seen UDP-carbohydrate?
Problem 19
In human liver extracts, the catalytic activity of glycogenin was detectable only after treatment with \(\alpha\) -amylase, an enzyme that hydrolyzes \(\alpha-1,4\) -glucosidic bonds. Why was \(\alpha\) -amylase necessary to reveal the glycogenin activity?
Problem 20
A sample of glycogen from a patient with liver disease is incubated with orthophosphate, phosphorylase, the transferase, and the debranching enzyme \((\alpha-1,6-\text { glucosidase }) .\) The ratio of glucose 1 -phosphate to glucose formed in this mixture is \(100 .\) What is the most likely enzymatic deficiency in this patient?
