Prostaglandin E1 binds to Z protein of rat liver

Abstract
Z protein or fatty‐acid‐binding protein is abundant in the cytosol of many cell types including liver cells. It is considered to play an important role in intracellular transport and metabolism of long‐chain fatty acids and other organic anions. We studied the role of Z protein in the metabolism of prostaglandin E1 (PGE1). Binding of tritiated prostaglandin E1 to this fatty‐acid‐binding protein (Z protein) purified from rat liver was determined. The binding of [3H]prostaglandin E1 to Z protein is rapid, saturable and reversible. Scatchard analysis of [3H]PGE1 binding to Z protein showed a single class of binding sites with a dissociation constant (Kd) of 37 nM. The binding capacity is 110 nmol/mg Z protein. Optimal [3H]PGE1 binding occurred at pH 7.4. The presence of 3 mM MgCl2 stimulated the prostaglandin E1 binding to Z protein. Competition experiments show that the binding of this autacoid to Z protein is highly specific. It could not be displaced by other prostaglandins (PGA1, PGA2, PGE2, PGB1, PGI2, PGD2, PGF, and 6‐ketoPGF). Z protein might be involved in the metabolism of prostaglandins in the cytosol.

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