Quantitation of plasma membrane fatty acid-binding protein by enzyme dilution and monoclonal antibody based immunoassay |
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Authors: | Sheng-Li Zhou Barry J Potter Decherd Stump Dario Sorrentino Paul D Berk |
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Affiliation: | (1) Departments of Medicine (Division of Liver Diseases) in Biochemistry, Mount Sinai School of Medicine of the City University of New York, 10029 New York, NY, USA;(2) Division of Liver Diseases, Mount Sinai School of Medicine, 1 Gustave L. Levy Place, Box 1079, 10029 New York, NY, USA |
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Abstract: | Summary A plasma membrane fatty acid-binding protein (h-FABPPm) has been isolated from rat hepatocytes. Analogous proteins have also been identified in adipocytes, jejunal enterocytes and cardiac myocytes, all cells with high transmembrane fluxes of fatty acids. These 43 kDa, highly basic (pl = 9.1) FABPpm 's appear unrelated to the smaller, cytosolic FABP's (designated FABP's) identified previously in the same tissues. h-FABPpm appears closely related to the mitochondrial isoform of glutamic-oxaloacetic transaminase (mGOT), and both the purified protein and liver cell plasma membranes (LPM) possess GOT enzymatic activity. From their relative GOT specific activities it is estimated that h-FABPpm constitutes approximately 2% of LPM protein, or about 0.7 × 107 sites per cell. A monoclonal antibody-based competitive inhibition enzyme immunoassay (CIEIA) for h-FABPpm is described; it yields an estimate of 3.4 x 107 h-FABPpm sites per hepatocyte. Quantitated by either method, h-FABPPm appears to be a highly abundant protein constituent of LPM. |
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Keywords: | fatty acids fatty acid-binding protein(s) hepatocyte immunoassay plasma membranes transport |
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