Macroamylasemia: variable response of a 7S and a 11S macroamylase to phosphate-benzoic acid buffer during gel filtration.

During thin layer or macrocolumn gel filtration with Sephadex G 200, a 7S macroamylase dissociated completely to normal-sized amylase when the eluant was phosphate-benzoic acid buffer. In contrast a 11S macroamylase was not affected by the buffer and amylase activity was associated with 11S proteins. Since phosphate-benzoic acid buffer is used in a thin layer screening method described by Peeters et al. (9), some macroamylases may go undetected. After treatment of the 7S macroamylase with phosphate-benzoic acid buffer, the amylase-free 7S proteins obtained formed macroamylase with added pancreatic amylase. This indicates that the buffer did not inhibit the activity of the macroamylase, but caused a dissociation of the macroamylase during gel filtration. The difference in the effect of phosphate-benzoic acid buffer on the two types of macroamylases may be attributed to the difference in affinity of binding proteins for the amylase molecule.

Activity of gamma-glutamyl transpeptidase in serum of patients receiving anticonvulsant of anticoagulant therapy.

1. Effects of chronic anticoagulant therapy in heart patients and anticonvulsant therapy in epileptics on gamma-glutamyl transpeptidase activity in serum were investigated. 2. The enzyme was elevated in 22% of 18 patients receiving anticoagulants. In these patients prothrombin time was also abnormally high. 3. 84% of 65 epileptics exhibited elevated gamma-glutamyl transpeptidase activity, 67% of which were not associated with elevated alkaline phosphatase or aspartate aminotransferase activities. In these latter cases, involvement of the liver was not apparent. 4. Possible relationships of anticonvulsant mediated enzyme induction or hepatic toxicity to elevated gamma-glutamyl transpeptidase activity in serum in epileptics is discussed.

Action of phenobarbital and carbon tetrachloride on hepatic microsomal inosine diphosphatase in the rat.

Pretreatment of rats with phenobarbital decreased the in vitro activity of liver microsomal inosine diphosphatase, whereas CCl4 caused an opposite effect. These actions were essentially abolished when the activity of the enzyme was assayed in the presence of optimal concentrations of triton X-100. The detergent was shown to activate and solubilize the enzyme along with membrane protein and phospholipids. During solubilization there was a tendency towards a greater phosphatidylcholine and lower phosphatidylethanolamine content in triton-soluble membranes. Microsomes of phenobarbital-treated rats were more resistant to triton solubilization, whereas those from CCl4-treated rats were more susceptible than the controls. These results demonstrated a loose association between the enzyme and the endoplasmic reticulum and that phenobarbital or CCl4 altered the activity of IDP-ase probably by affecting the binding of the enzyme to the structure skeleton of the membrane. The role of phospholipid changes in the stability of microsomal membranes is discussed.