Implication of BBM lipid composition and fluidity in mitigated alkaline phosphatase activity in renal cell carcinoma

Previous study has documented reduced alkaline phosphatase (ALP) activity in brush border membrane (BBM) isolated from renal cell carcinoma (RCC). Diminished activity of ALP is associated with alteration in both increased K(m) as well as decreased V(max) of enzyme suggests that there may be a change in the conformation of enzyme as well as decreased number of ALP active molecules. The present study was conducted to find out any role of BBM lipid composition and its fluidity in diminished activity of alkaline phosphatase in renal cell carcinoma. Total phospholipids and glycolipids were significantly augmented in BBM from RCC as compared to control. Fractional analysis of total phospholipids revealed significantly increased phosphatidylethanolamine. Decreased fractions of sphingomyelin and phosphatidylinositol were observed. Cholesterol-to-total phospholipid molar ratios in tumor BBM was a significantly lower in tumor BBM. A significant reduction in polarization and microviscosity was found in BBM from RCC. Therefore, we conclude that alteration in membrane lipid composition and fluidity may play a substantial role in reduced activity of ALP in RCC.