| 1. |
- Ekman, Pia, et al.
(författare)
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Phosphorylation of glucokinase from rat liver in vitro by protein kinase A with a concomitant decrease of its activity
- 1988
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Ingår i: Archives of Biochemistry and Biophysics. - : Elsevier BV. - 0003-9861 .- 1096-0384. ; 261:2, s. 275-282
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Tidskriftsartikel (refereegranskat)abstract
- Glucokinase, purified from rat liver, was phosphorylated to an extent of 1 mol [32P]-phosphate/mol of enzyme when incubated with [32P]ATP and protein kinase A from pig or rabbit muscle. The phosphate was bound to serine residues. K0.5 increased and Vmax decreased upon phosphorylation. The phosphate group was removed during incubation of the phosphorylated glucokinase with alkaline phosphatase. Enzymatically inactive glucokinase was not phosphorylated by the protein kinase.
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| 2. |
- Nilsson Ekdahl, Kristina
(författare)
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In vitro phosphorylation of fructose-1,6-bisphosphatase from rabbit and pig liver with cyclic AMP-dependent protein kinase
- 1988
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Ingår i: Archives of Biochemistry and Biophysics. - : Elsevier BV. - 0003-9861 .- 1096-0384. ; 262:1, s. 27-31
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Tidskriftsartikel (refereegranskat)abstract
- Homogeneous preparations of fructose-1,6-bisphosphatase from mouse, man, rabbit, pig, and rat were tested as substrates for cyclic AMP-dependent protein kinase. Up to 1 mol of [32P]phosphate per mole enzyme subunit was incorporated into fructose-1,6-bisphosphatase from pig and rabbit liver, which should be compared with 2.6 mol of phosphate per mole enzyme subunit in the case of the rat liver enzyme. The phosphorylation of fructose-1,6-bisphosphatase from the livers of man and mouse was negligible. Phosphorylation of pig and rabbit fructose-1,6-bisphosphatase decreased the apparent Km for fructose-1,6-bisphosphate, but in contrast to the case of the rat liver enzyme it did not change the inhibition constants for AMP and fructose-2,6-bisphosphate. The Phosphorylation sites in rabbit and pig liver fructose-1,6-bisphosphatase were located close to the carboxyterminal of the polypeptide chains, since trypsin treatment of the phosphorylated enzyme quantitatively removed all of the protein-bound radioactivity without significantly altering the subunit molecular weight and with a maintained neutral pH Optimum.
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| 3. |
- Persson, Bengt L., et al.
(författare)
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Energy-linked nicotinamide nucleotide transhydrogenase. Hydrodynamic properties and active form of purified and membrane-bound mitochondrial transhydrogenase from beef heart
- 1987
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Ingår i: Archives of Biochemistry and Biophysics. - : Elsevier BV. - 0003-9861 .- 1096-0384. ; 259:2, s. 341-349
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Tidskriftsartikel (refereegranskat)abstract
- The mitochondrial nicotinamide nucleotide transhydrogenase from beef heart was investigated with respect to minimal assembly of the purified enzyme and of the enzyme in the mitochondrial inner membrane. Studies of the hydrodynamic properties of the purified enzyme in the presence of 0.3% Triton X-100 allowed determination of the Stokes radius, sedimentation constant, partial specific volume, frictional ratio, and molecular weight. Under these conditions transhydrogenase existed as an inactive monomer, suggesting that monomerization may be accompanied by inactivation. Radiation inactivation was used to determine the functional molecular size of purified detergent-dispersed transhydrogenase and transhydrogenase in beef heart submitochondrial particles. Under these conditions the catalytic activity of both the purified and the membrane-bound enzyme was found to be catalyzed by a dimeric form of the enzyme. These results suggest for the first time that the minimal functional assembly of detergent-dispersed as well as membrane-bound transhydrogenase is a dimer, which is not functionally associated with, for example, complex I or ATPase. In addition, the results are consistent with the possibility that the two subunits of transhydrogenase are catalytically active in an alternating fashion according to a previously proposed half-of-the-sites reactivity model.
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| 4. |
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| 5. |
- Lohmander, Stefan, et al.
(författare)
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Post-translational events in proteoglycan synthesis : Kinetics of synthesis of chondroitin sulfate and oligosaccharides on the core protein
- 1986
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Ingår i: Archives of Biochemistry and Biophysics. - : Elsevier BV. - 0003-9861. ; 250:1, s. 211-227
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Tidskriftsartikel (refereegranskat)abstract
- Chondrocytes isolated from the Swarm rat chondrosarcoma were incubated in culture with [1-3H]glucose for 30 min to 8 h. Labeled proteoglycans were isolated, treated with borohydride under alkaline conditions, and the three complex sugar structures purified: N- and O-linked oligosaccharides and chondroitin sulfate chains. The amount of incorporated radioactivity into each component sugar was analyzed by HPLC after enzyme digestion and hydrolysis. The kinetic data for labeling of each sugar over the time course of the experiment were fit to first-order rate equations and the half times (t 1 2) to linear labeling were calculated. The t 1 2 values were essentially the same, 5-8 min, for galactose in all three complex sugar structures and for chain glucuronic acid in chondroitin sulfate, while that for xylitol in chondroitin sulfate, 15.8 min, was significantly longer. Thus, oligosaccharide synthesis is concomitant with chondroitin sulfate chain synthesis; the addition of the chondroitin sulfate linkage galactose occurs at or nearly at the same time as chain elongation while the addition of linkage xylose residues to the core protein may precede chain synthesis by up to 8 min. Since the intracellular t 1 2 of the core protein precursor for these cells is 45 to 90 min, the data strongly suggest that the addition of xylose is not completed to any significant extent while the polypeptide is still nascent or shortly after its release into the rough endoplasmic reticulum. It is proposed that the addition of xylose to the core protein precursor is a late endoplasmic reticulum or early Golgi event. The analytical data were consistent with the presence of ester phosphate on about 80% of the xylose residues of the newly synthesized proteoglycan.
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| 6. |
- Sabharwal, Hemant, et al.
(författare)
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Oligosaccharides from feces of preterm infants fed on breast milk
- 1988
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Ingår i: Archives of Biochemistry and Biophysics. - : Elsevier BV. - 0003-9861. ; 265:2, s. 390-406
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Tidskriftsartikel (refereegranskat)abstract
- Nine neutral and five acidic oligosaccharides were isolated from feces of a preterm (30th postmenstrual week) blood group A nonsecretor infant fed on pooled breast milk. Structural analyses were carried out using sugar and methylation analyses, fast atom bombardment mass spectrometry, and 1H NMR. The acidic oligosaccharides are well-known components of human milk. The neutral oligosaccharides are characteristic of nonsecretor milk. Surprisingly, no secretor gene-dependent oligosaccharides were present in the feces. Another preterm (27th postmenstrual week) blood group A, secretor infant fed on pooled breast milk showed the same fecal oligosaccharide pattern as above during the first week after birth, despite being a secretor individual. Also notable was the absence of blood group A-active oligosaccharides in this sample. Another sample of feces collected 8 weeks later from the latter infant contained the expected blood group A-active oligosaccharides. Furthermore, free sialic acid was present at the cost of the sialyl oligosaccharides seen earlier. Thus, infants born prematurely do not show the same degree of development of oligosaccharide metabolism as their more mature counterparts.
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