Skip to Content
Merck
  • Influence of the physical state of the membrane on the enzymatic activity and energy of activation of protein kinase C alpha.

Influence of the physical state of the membrane on the enzymatic activity and energy of activation of protein kinase C alpha.

Biochemistry (1999-07-01)
A M Jiménez-Monreal, F J Aranda, V Micol, P Sánchez-Piñera, A de Godos, J C Gómez-Fernández
ABSTRACT

The activation of protein kinase C alpha was studied by using a lipid system consisting of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine (POPS) (molar ratio 4:1) and different proportions of 1-palmitoyl-2-oleoyl-sn-glycerol (POG). The phase behavior of the lipidic system was characterized by using differential scanning calorimetry and 31P NMR, and a phase diagram was elaborated. The results suggested the formation of two diacylglycerol/phospholipid complexes, one at 15 mol % of POG and the second at 30 mol % of POG. These two complexes would define the three regions of the phase diagram: in the first region (concentrations of POG lower than 15 mol %) there is gel-gel immiscibility at temperatures below that of the phase transition between C1 and pure phospholipid, and a fluid lamellar phase above of the phase transition. In the second region (between 15 and 30 mol % of POG), gel-gel immiscibility between C1 and C2 with fluid-fluid immiscibility was observed, while inverted hexagonal HII and isotropic phases were detected by 31P NMR. In the third region (concentrations of POG higher than 30 mol %), gel-gel immiscibility seemed to occur between C2 and pure POG along with fluid-fluid immiscibility, while an isotropic phase was detected by 31P NMR. When PKC alpha activity was measured, as a function of POG concentration, maximum activity was found at POG concentrations as low as 5-10 mol %; the activity slightly decreased as POG concentration was increased to 45 mol % at 32 degrees C (above Tc) whereas activity did not change with increasing concentrations of POG at 5 degrees C (below Tc). When the activity was studied as a function of temperature, at different POG concentrations, and depicted as Arrhenius plots, it was found that the activity increased with increasing temperatures, showing a discontinuity at a temperature very close to the phase transition of the system and a lower activation energy at the upper slope of the graph, indicating that the physical state of the membrane affected the interaction of PKC alpha with the membrane.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
1-Oleoyl-2-palmitoyl-sn-glycero-3-phosphocholine, ≥98% (GC), ≥99% (TLC)
SKU
Pack Size
Availability
Price
Quantity