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Biomedical subjects

C Taylor

Publications and source records attributed to C Taylor.

At least 379 records · Page 21Linked to original sources
PubMed1975

Debranching enzyme from rabbit skeletal muscle. Purification, properties and physiological role.

Debranching enzyme was purified 150-fold from rabbit skeletal muscle by a three-step procedure which utilised ammonium sulphate precipitation, ion-exchange chromatography on DEAE-cellulose and "hydrophobic" chromatography on Sepharose-NH(CH2)4NH2. The preparation was completed within three days, and 200 mg enzyme was isolated from 1000 g muscle, which represented an overall yield of 60%. The preparation was homogeneous by the criteria of polyacrylamide gel electrophoresis and ultracentrifugal analysis. The sedimentation coefficient, s20,w, was 8.1 S. The amino acid composition was determined, and the absorption coefficient, A280 1%, measured refractometrically was 17.5. The subunit molecular weight determined by gel electrophoresis in the presence of sodium dodecyl sulphate was 166000 and this value was supported by sedimentation equilibrium in the presence of 6 M guanidinium chloride (1550oo). The molecular weight of the native enzyme measured by high-speed sedimentation equilibrium was 164000, showing that the debranching enzyme is a monomeric protein at the concentrations which exist in muscle (0.7 mg/ml). The results indicate that the two different enzyme activities which are associated with debranching enzyme, 1,4-glucan-4-glycosyltransferase and amylo-1,6-glucosidase, reside on the same polypeptide chain. Protein-glycogen particles isolated from skeletal muscle showed seven major protein-staining components by polyacrylamide gel electrophoresis, one of which was identified as debranching enzyme. ,our of the other components were the alpha and beta subunits of phosphorylase kinase, glycogen phosphorylase and glycogen synthetase. A new titrimetric assay for debranching enzyme was developed; it was used to demonstrate that the maximum potential activity of debranching enzyme is only 5--10% that of phosphorylase at the concentrations of the two enzymes in skeletal muscle. Since the activity of debranching enzyme is unaffected by every mechanism which leads to the activation of glycogen phosphorylase and phosphorylase kinase, the evidence suggests that the hormonal control of muscle glycogenolysis by adrenalin might be confined to a stimulation of rate of degradation of the outermost branches of glycogen.

Amino Acids↗
PubMed1975

Development of a radioimmunoassay for alpha-melanocyte-stimulating hormone in the rat.

A sensitive and specific radioimmunoassay for alpha-melanocyte-stimulating hormone (alpha-MSH) was developed. Extracts of the neurointermediate lobe of the rat produced displacement curves which were parallel to those obtained with synthetic alpha-MSH. The mean immunoreactive alpha-MSH concentration in neurointermediate lobes from normal adult rats was 2768 +/- 200 (S.E.M.) ng/lobe. This accounted for approximately 78% of the MSH activity of the neurointermediate lobe as measured by bioassay. Much lower levels of immunoreactive alpha-MSH were found in the anterior lobe of the rat. Extracts of rat serum and plasma also contained immunoreactive alpha-MSH and the mean level was found to be 237 +/- 20 pg/ml. This was slightly lower than the level measured in rat plasma by bioassay. Increased levels of alpha-MSH were found in plasma of rats 1 and 3 h after a single injection of trifluoperazine and after 1-5 min of ether anaesthesia. These changes were reflected by decreases in the alpha-MSH content of the neurointermediate lobe.

Adrenocorticotropic Hormone↗