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O Ben-Zeev

Publications and source records attributed to O Ben-Zeev.

22 records · Page 2Linked to original sources
PubMed1983

Lipoprotein lipase: size of the functional unit determined by radiation inactivation.

Radiation inactivation was used to determine the functional molecular weight of lipoprotein lipase (LPL) in rat heart and adipose tissues. This technique reveals the size of the smallest unit required to carry out the enzyme function. Supernatant fractions of the tissue homogenates were exposed to high energy electrons at -135 degrees C. LPL activity showed a simple exponential decay in all samples tested. Because changes in nutritional state shift the distribution of LPL between the capillary endothelial and parenchymal cells within heart and adipose tissues, fasted and refed rats were used for the radiation studies. The functional molecular weight was calculated to be 127,000 +/- 15,000 (mean +/- SD) daltons for heart and adipose. Thus, the smallest unit required for enzyme function was the same in both of these tissues and did not vary with nutritional state. The data suggest that, compared with LPL monomer sizes reported in the range 55,000 to 72,000, this active unit constitutes a dimer.

Adipose Tissue↗
PubMed1981

Heparin-releasable and nonreleasable lipoprotein lipase in the perfused rat heart.

Lipoprotein lipase released from the rat heart during a 30-s perfusion with heparin was compared to the lipase remaining in the heart tissue. The perfusate, containing the heparin-releasable enzyme, as well as the heart tissue extract ("residue"), was purified on heparin-Sepharose affinity columns. Both purified fractions showed pronounced inhibition by 1 M NaCl and by antiserum to heart lipoprotein lipase, thus displaying mainly lipoprotein lipase activities. However, their apparent Km values for triglyceride differed significantly (perfusate, 0.4 mM; residue, 4.0 mM). Also, the pattern of the immunotitration curves for the two fractions differed, the perfusate being more susceptible to antibody inhibition than the residue. Addition of heparin (0.5 unit/ml) inhibited the perfusate activity up to 60%, whereas the residual activity was actually stimulated by 15%. Based on these findings, we propose that the heart tissue contains a less active, low affinity enzyme form, possibly representing the precursor of the high affinity, functional, endothelial-bound lipoprotein lipase.

Animals↗