Search PubMed⌕ Search

Biomedical subjects

J Goris

Publications and source records attributed to J Goris.

At least 109 records · Page 6Linked to original sources
PubMed1983

Modulation of latent protein phosphatase activity from vascular smooth muscle by histone-H1 and polylysine.

An apparently latent phosphatase which migrated as a protein of Mr 130,000 during sucrose density centrifugation, and a spontaneously active phosphatase (Mr 68,000) were isolated from bovine aortic smooth muscle. Basal phosphorylase phosphatase activity of the latent preparations was stimulated 12 fold by low concentrations of lysine-rich histone-H1 (30 micrograms/ml) and 6 fold by polylysine (Mr 17,000; 12 micrograms/ml), whereas the spontaneously active enzyme was only slightly affected. The enzymatic activity of the spontaneously active preparation was completely destroyed by beta-mercaptoethanol. In contrast, the apparently latent enzyme was converted to a more active form of lower molecular weight (Mr 86,000) following treatment with beta-mercaptoethanol and this form of the enzyme was still stimulateable by histone-H1. These findings show that the aortic spontaneous and apparently latent phosphatase actives are ascribable to separate enzymes and they suggest that the activity of latent phosphatase in living cells may be modulated by cationic proteins such as histones or similar effector molecules.

Animals↗
PubMed1983

Role of the deinhibitor protein in the interconversion of the ATP,Mg-dependent protein phosphatase.

The small molecular weight (+/- 9,000) heat stable deinhibitor protein, isolated from dog liver, not only protects the multisubstrate protein phosphatase from inhibition by inhibitor-1 and the modulator protein. It prevents the conversion of the active enzyme to the ATP,Mg-dependent enzyme form brought about by the modulator protein, and also affects the activation of the ATP,Mg-dependent protein phosphatase, probably by stabilizing the enzyme in its active conformation during the reversible activation by protein kinase FA. Therefore the deinhibitor protein could be an important factor in the process of glycogen synthesis, which requires glycogen synthase and phosphorylase as dephosphorylated enzymes.

Adenosine Triphosphate↗
PubMed1981

The MgATP-dependent protein phosphatase and protein phosphatase 1 have identical substrate specificities.

The MgATP-dependent phosphorylase phosphatase was found to have a broad substrate specificity. Its activity against all phosphoproteins tested was dependent upon preincubation with the activating factor FA and MgATP. The enzyme dephosphorylated and inactivated phosphorylase kinase and inhibitor 1, and dephosphorylated and activated glycogen synthase and acetyl-CoA carboxylase. Glycogen synthase was dephosphorylated at similar rates whether it had been phosphorylated by cyclic-AMP-dependent protein kinase, phosphorylase kinase or glycogen synthase kinase 3. The enzyme also catalysed the dephosphorylation of ATP citrate lyase, initiation factor eIF-2, and troponin I. The properties of the MgATP-dependent protein phosphatase from either dog liver or rabbit skeletal muscle showed a remarkable similarity to highly purified preparations of protein phosphatase 1 from rabbit skeletal muscle. The relative activities of the two enzymes against all phosphoproteins tested was very similar. Both enzymes dephosphorylated the beta-subunit of phosphorylase kinase 40-fold faster than the alpha-subunit, and both enzymes were inhibited by identical concentrations of the two proteins termed inhibitor 1 and inhibitor 2, which inhibit protein phosphatase 1 specifically. These results demonstrate that the MgATP-dependent protein phosphatase is a type-1 protein phosphatase, and is distinct from type-2 protein phosphatases which dephosphorylate the alpha-subunit of phosphorylase kinase and are unaffected by inhibitor 1 and inhibitor 2. The possibility that the MgATP-dependent protein phosphatase is an inactive form of protein phosphatase 1 and that both proteins share the same catalytic subunit is discussed.

Adenosine Triphosphate↗
PubMed1980

ATP x Mg-dependent protein phosphatase from rabbit skeletal muscle. I. Purification of the enzyme and its regulation by the interaction with an activating protein factor.

An ATP x Mg-dependent protein phosphatase (FC) was purified to near homogeneity from rabbit muscle. The enzyme was completely devoid of any spontaneous activity but could be activated by a protein activator (FA) in the presence of ATP and Mg ions. The inactive phosphatase migrated as a single protein band on sodium dodecyl sulfate-gel electrophoresis, and in discontinuous gel electrophoresis, where the potential phosphatase activity was located in the main protein band. The molecular weight determined by sodium dodecyl sulfate electrophoresis or by sucrose density centrifugation was found to be 70,000. FC migrated on gel filtration as a 140,000 molecular weight species. The activation by FA was not paralleled by an incorporation of [32P]-phosphate into the ATP x Mg-dependent phosphatase, and from the kinetics of activation a protein-protein interaction with ATP x Mg as a necessary factor, can be inferred as the mechanism of activation. After activation by FA and ATP X Mg, the purified enzyme had a specific activity of 10,000 units/mg of protein, and a Km for rabbit muscle phosphorylase a of approximately 1.0 mg/ml. The activated enzyme did not release [32P]phosphate from 32[-labeled rabbit muscle synthase b, prepared from glucagon-treated dogs. It did, however, remove all the 32P label from phosphorylase b kinase, autophosphorylated to the level of 2.0 mol/mol of 1.3 X 10(6) molecular weight.

Adenosine Triphosphate↗
PubMed1980

ATP x Mg-dependent protein phosphatase from rabbit skeletal muscle. II. Purification of the activating factor and its characterization as a bifunctional protein also displaying synthase kinase activity.

A protein (FA) has been isolated from rabbit muscle which has two functions: one is the activation of the ATP x Mg-dependent phosphatase (see previous paper) (1) and the second is the phosphorylation and concomitant inactivation of glycogen synthase, independent from cyclic AMP or Ca ions. The two activities co-purify throughout the purification scheme, and reside in the single protein band that the purified preparation shows in discontinuous acrylamide gel electrophoresis. Heat inactivation experiments with the purified protein showed a parallel decrease of both activities with time. GTP could efficiently replace the ATP in both reactions. Sodium dodecyl sulfate-gel electrophoresis also shows a single protein-stained band corresponding to a Mr = approximately 50,000 and sucrose density gradient centrifugation gave a value of 45,000. The enzyme incorporates only 1 mol of phosphate/mol of synthase monomer (85,000 daltons) and brings the activity ratio (+/- glucose-6-P) down to less than 0.05. Kinetic studies suggest that FA exerts its two activities in quite different ways: the activation of the ATP x Mg-dependent phosphatase is bought about by a protein-protein interaction (FA x FC complex formation) with ATP x Mg as a necessary cofactor, whereas for the inactivation of synthase, FA is a cyclic AMP- and Ca-independent kinase.

Adenosine Triphosphate↗