Barbara Illingworth

The isolation of pyridoxal-5-phosphate from crystalline muscle phosphorylase

Abstract Dialyzed and Norit-treated muscle phosphorylase a, after recrystallization from versene-glycerophosphate, contains 8 organic phosphate groups per mole or 2 phosphate groups per subunit of molecular weight of 125,000. Four of these phosphate groups are extracted by precipitation of the enzyme with trichloroacetic or perchloric acid. The extracted phosphate compound was isolated as the barium salt and identified as pyridoxal-5-phosphate by its spectrum and by specific enzymic tests. Column chromatography of the trichloroacetic acid extract and paper electrophoresis did not reveal the presence of other phosphorylated compounds. In particular, pyridoxamine-5-phosphate, adenylic acid and other nucleotides could not be detected. Free pyridoxal, pyridoxamine or pyridoxine were also absent.

The effect of epinephrine and other glycogenolytic agents on the phosphorylase A content of muscle

Abstract 1. Injection of epinephrine in rats caused a marked rise in the phosphorylase a content of muscle. Nor-epinephrine had the same effect but required much larger doses. 2. Epinephrine prevented the complete disappearance of phosphorylase a in a fatigued muscle and accelerated the resynthesis of phosphorylase a during recovery from fatigue. 3. The concentration of active phosphorylase a in thin frog muscles, incubated in a solution containing epinephrine, aerobically or anaerobically rose at the expense of inactive phosphorylase b . 4. Versene inhibited the above rise. 5. The glycogenolytic agents dinitrophenol and caffeine reduced the phosphorylase a content when it was high and caused no change when it was low.

Phosphorylase and uridinediphosphoglucose-glycogen transferase in pyridoxine deficiency

Abstract The total phosphorylase activity of the skeletal muscle of rats maintained on a pyridoxine deficient diet has been found to fall to 35% of the normal value. The phosphorylase a activity of the tissue of these rats has the normal value, and the glycogen content of the muscles of such deficient rats is not different from that of control animals. The apparent activity of uridine diphosphoglucose-glycogen transferase is not changed from the normal level in pyridoxine deficiency.

Enzymatic Defects as Causes of Hypoglycemia

A review of some of the enzymatic causes of hypoglycemia is presented. Evidence that there may be a diminished production of epinephrine or glucagonin certain cases of hypoglycemia is reviewed and the relationship of these hormones to the activation of glycogen phosphorylase is discussed. Galactosemia, fructose intolerance and glycogen storage diseases are cited as examples of hereditary disorders attributable to specific enzyme defects and often accompanied by hypoglycemia. The deficiencies of galactose-1-phosphate uridyl transferase in galactosemia and aldolase in fructose intolerance result in the accumulation in the tissues of toxic quantities of intermediary metabolites (galactose-1-phosphate and fructose-1-phosphate, respectively) which secondarily affect the activities of other enzymes. In Type I glycogenosis, the hypoglycemia is explained by the deficiency of glucose-6-phosphatase. Other types of glycogenoses often provide examples of intermittent hypoglycemia. The role of gluconeogenesis in the maintenance of blood sugar levels has not been reviewed.