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K F Chan

Publications and source records attributed to K F Chan.

68 records · Page 4Linked to original sources
PubMed1982

Rabbit skeletal muscle phosphorylase kinase. Interactions between subunits and influence of calmodulin on different complexes.

Aspects of the molecular interaction and subunit structure of rabbit skeletal muscle phosphorylase kinase, (alpha beta gamma delta)4, were investigated. Exogenous addition of the delta subunit (calmodulin) stimulated the activities of nonactivated phosphorylase kinase and the alpha gamma delta complex, but not the gamma delta complex. This stimulatory effect does not seem to affect the activity-pH profile of the native kinase and is expressed at least partly through an interaction of the calmodulin with the alpha subunit, resulting in an increase in the apparent Vm parameters. Low concentrations of trifluoperazine had only slight effect on the activities of the three forms of kinase, whereas high concentrations caused nonspecific inactivation. The effects of trifluoperazine and EGTA on the activities of the alpha gamma delta and gamma delta complexes were additive; together, they inactivated the two complexes to about 10% of their original activities. The delta subunit remained tightly bound to phosphorylase kinase and the alpha gamma delta complex, even in the presence of 8 M urea, but less so with the gamma delta complex. The nonactivated kinase is more stable towards heat inactivation at 37 degrees C than the alpha gamma delta complex, whereas the gamma delta complex is least stable. Similar to the holoenzyme, limited trypsin digestion activated the alpha gamma delta complex. The pH 6.8/8.2 activity ratio of this complex increased from 0.5 to 0.9, with concomitant degradation of the alpha subunit. In contrast, the gamma delta complex is fairly inert to limited proteolysis. By using sucrose density gradient ultracentrifugation and pretreatment of the gamma delta complex with EGTA, results indicated that the gamma subunit may be a Ca2+-independent kinase, which has about 30% of the original phosphorylase kinase activity.

Animals↗
PubMed1982

Phosphorylase kinase specificity. A comparative study with cAMP-dependent protein kinase on synthetic peptides and peptide analogs of glycogen synthase and phosphorylase.

A synthetic pentadecapeptide, Pro-Leu-Ser-Arg-Thr-Leu-Ser-Val-Ser-Ser-Leu-Pro-Gly-Leu-Glu, corresponding to the phosphorylatable site at the NH2 terminus of glycogen synthase, could be phosphorylated stoichiometrically at seryl residue 7 by both phosphorylase kinase and cAMP-dependent protein kinase. Phosphorylation of seryl residue 3 also occurred after prolonged incubation with cAMP-dependent protein kinase. Kinetic studies show that the pentadecapeptide is a better substrate for phosphorylase kinase. A peptide consisting of residues 1-11 was not as good a substrate and substitution of Arg-4 by Lys and Ser-9 by ARg in the unidecapeptide decreased and increased phosphorylase kinase reaction rates, respectively. Higher rates of phosphorylation were obtained with peptides of the phosphorylatable site of phosphorylase. A peptide with the sequence, Leu-Ser-Tyr-Arg-Arg-Tyr-Ser-Leu was phosphorylated initially by phosphorylase kinase and cAMP-dependent protein kinase at Ser-2 and Ser-7, respectively. Upon longer incubation, second site phosphorylation occurred with both kinases. A peptide of the same sequence with D-amino acids could not be phosphorylated but was a competitive inhibitor of both enzymes. The results suggest that optimal interaction of the two kinases depends on various factors including the orientation of arginyl groups with respect to the phosphorylatable serine.

Amino Acid Sequence↗
PubMed1982

Annular pancreas.

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Acute Disease↗
PubMed1981

Case report 159.

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Giant Cell Tumors↗
PubMed1980

Case report 109.

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Acromegaly↗
PubMed1979

Case report 87.

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Calcinosis↗
PubMedDate not supplied

Widespread occurrence of ganglioside-stimulated protein kinase in animal brains.

Ganglioside-stimulated protein kinase, designated PKJ, had been found in several animal brains. These include guinea pig, rabbit, rat, and duck brains. All of the four brain PKJ could be extracted from the particulate fractions using nonionic detergent nonidet P-40 and purified by using identical DEAE-cellulose and phenyl-Sepharose chromatographic methods. These results suggest that PKJ from different animal brains has similar ionic and hydrophobic characteristics. All four of the partially purified PKJ preparations could undergo autophosphorylations in the presence of trisialoganglioside GT1b and 32P-ATP. Analyses of the autophosphorylated proteins by using SDS-polyacrylamide gel electrophoresis and subsequent autoradiography revealed one major radioactive band with apparent M(r) = 68,000. The range of ganglioside-stimulated autophosphorylation was between 6- and 10-fold. The structural similarities of the different animal brain PKJ were further determined by using one-dimensional peptide mapping techniques. Limited proteolytic cleavages of the 32P-labeled 68-kD bands with staphylococcal aureus V-8 protease resulted in four major radioactive fragments with apparent M(r) corresponding to 22, 20, 18 and 15 kD, respectively. By contrast, digestion with chymotrypsin revealed only two major radioactive bands with apparent M(r) of 43 and 26 kD, respectively. These findings indicate that PKJ from guinea pig, rabbit, rat, and duck brains may have similar primary structures.

Animals↗