scholarly journals Low immunogenicity of the common lipoamide dehydrogenase subunit (E3) of mammalian pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase multienzyme complexes

1985 ◽  
Vol 226 (2) ◽  
pp. 509-517 ◽  
Author(s):  
O L De Marcucci ◽  
A Hunter ◽  
J G Lindsay
Keyword(s):  
Rat Liver ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Sodium Dodecyl ◽  
Normal Component ◽  
Proteolytic Fragment ◽  
Multienzyme Complexes ◽  
The Common ◽  
Oxoglutarate Dehydrogenase ◽  
Lipoamide Dehydrogenase

The production of high-titre monospecific polyclonal antibodies against the purified pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase multienzyme complexes from ox heart is described. The specificity of these antisera and their precise reactivities with the individual components of the complexes were examined by immunoblotting techniques. All the subunits of the pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complexes were strongly antigenic, with the exception of the common lipoamide dehydrogenase component (E3). The titre of antibodies raised against E3 was, in both cases, less than 2% of that of the other subunits. Specific immunoprecipitation of the dissociated N-[3H]ethylmaleimide-labelled enzymes also revealed that E3 alone was absent from the final immune complexes. Strong cross-reactivity with the enzyme present in rat liver (BRL) and ox kidney (NBL-1) cell lines was observed when the antibody against ox heart pyruvate dehydrogenase was utilized to challenge crude subcellular extracts. The immunoblotting patterns again lacked the lipoamide dehydrogenase band, also revealing differences in the apparent Mr of the lipoate acetyltransferase subunit (E2) from ox kidney and rat liver. The additional 50 000-Mr polypeptide, previously found to be associated with the pyruvate dehydrogenase complex, was apparently not a proteolytic fragment of E2 or E3, since it could be detected as a normal component in boiled sodium dodecyl sulphate extracts of whole cells. The low immunogenicity of the lipoamide dehydrogenase polypeptide may be attributed to a high degree of conservation of its primary sequence and hence tertiary structure during evolution.

scholarly journals Purification of 2-oxo acid dehydrogenase multienzyme complexes from ox heart by a new method

1980 ◽  
Vol 191 (1) ◽  
pp. 147-154 ◽  
Author(s):  
C J Stanley ◽  
R N Perham
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Sodium Dodecyl ◽  
Tween 80 ◽  
New Method ◽  
Acid Dehydrogenase ◽  
Multienzyme Complexes ◽  
Oxoglutarate Dehydrogenase ◽  
Triton X ◽  
Dehydrogenase Complex

A new method is described that allows the parallel purification of the pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase multienzyme complexes from ox heart without the need for prior isolation of mitochondria. All the assayable activity of the 2-oxo acid dehydrogenase complexes in the disrupted tissue is made soluble by the inclusion of non-ionic detergents such as Triton X-100 or Tween-80 in the buffer used for the initial extraction of the enzyme complexes. The yields of the pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complexes are many times greater than those obtained by means of previous methods. In terms of specific catalytic activity, banding pattern on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, sedimentation properties and possession of the regulatory phosphokinase bound to the pyruvate dehydrogenase complex, the 2-oxo acid dehydrogenase complexes prepared by the new method closely resemble those described by previous workers. The greatly improved yield of 2-oxo acid dehydrogenase complexes occasioned by the use of Triton X-100 or Tween-80 as solubilizing agent supports the possibility that the bulk of the pyruvate dehydrogenase complex is associated in some way with the mitochondrial inner membrane and is not free in the mitochondrial matrix space.

scholarly journals Partial purification and characterization of a pyruvate dehydrogenase-complex-inactivating enzyme from rat liver

1978 ◽  
Vol 169 (2) ◽  
pp. 321-328 ◽  
Author(s):  
A Lynen ◽  
E Sedlaczek ◽  
O H Wieland
Keyword(s):  
Rat Liver ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Potassium Phosphate ◽  
Partial Purification ◽  
Acid Extraction ◽  
High Dilutions ◽  
Dehydrogenase Complex

An enzyme inactivating the pyruvate dehydrogenase complex (inactivase) was purified about 8000-fold from rat liver by differential centrifugation, acid extraction of a lysosomerich 25000 g pellet, acetone fractionation, and adsorption on calcium phosphate gel. By exclusion chromatography on Sephadex G-100 a molecular weight of 21 000 was estimated. The purified enzyme was most stable at pH 5.8 in potassium phosphate buffer, and at pH 4.5 in McIlvaine buffer. At high dilutions the enzyme was very labile and was remarkably stabilized by high salt concentrations. Enzyme activity is inhibited by native rat blood serum, iodoacetamide and leupeptin, but not by phenylmethanesulphonyl fluoride, suggesting that it belongs to the class of thiol proteinases. Among various enzymes tested, only 2-oxoglutarate dehydrogenase was attacked by the inactivase to a similar extent to the pyruvate dehydrogenase complex. Studies on the inactivation mechanism indicate that although the overall reaction is completely lost after treatment with inactivase, each individual step of the multienzyme complex retains full catalytic activity. As judged from sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, the transacetylase subunit appears to be degraded into several smaller fractions.

scholarly journals Studies on the incorporation of [32P]phosphate into pyruvate dehydrogenase in intact rat fat-cells. Effects of insulin

1980 ◽  
Vol 192 (2) ◽  
pp. 469-481 ◽  
Author(s):  
W A Hughes ◽  
R W Brownsey ◽  
R M Denton
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Subcellular Fractionation ◽  
Alpha Subunit ◽  
Fat Cells ◽  
Phosphorylated Proteins ◽  
Alpha Subunits ◽  
Dehydrogenase Complex

1. Intact rat epididymal fat-cells were incubated with 32Pi, and the intracellular proteins were separated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. One of the separated bands of phosphorylated proteins had an apparent subunit mol.wt. of 42 000, which is the same as that of the alpha-subunit of the pyruvate dehydrogenase complex. By using a combination of subcellular fractionation, immunoprecipitation with antiserum raised against pyruvate dehydrogenase complex and two-dimensional electrophoresis it was apparent that the incorporation into alpha-subunits accounted for 35–45% of the total incorporation into this band of phosphoproteins. 2. The increase in the initial activity of pyruvate dehydrogenase that follows brief exposure of fat-cells to insulin was shown to be associated with a decrease in the steady-state incorporation of 32P into the alpha-subunits of pyruvate dehydrogenase. 3. Tryptic peptide analysis of pyruvate dehydrogenase [32P]phosphate, labelled in intact fat-cells, indicated that three serine residues on the alpha-subunit were phosphorylated, corresponding to the three sites phosphorylated when purified pig heart pyruvate dehydrogenase was incubated with [gamma-32P]ATP. The relative phosphorylation of all three serine residues appeared to be similar in 32P-labelled alpha-subunits in both control and insulin-treated fat-cells.

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