[Properties and activation by lysophospholipids and fatty acid of membrane-bound guanylate cyclase in lymphocytes and erythrocytes from mouse spleen].

To clarify the properties of membrane-bound guanylate cyclase of lymphocytes and a functional role of lysophospholipids, the enzymic properties of membrane-bound guanylate cyclase and the effects of lysophospholipids and a free fatty acid with Ca2+ on the cyclase in lymphocyte and erythrocyte membrane fractions prepared from mouse splenic whole cells were examined. The membrane-bound guanylate cyclase activities of lymphocyte and erythrocyte membrane fractions from splenic whole cells were activated markedly by several lysophospholipids and linoleate. Lysophospholipids were divided into three groups according to their effects on the cyclase. 1) The first group of lysophospholipids exhibited the concentration-activity curve which was similar to that of linoleate. 2) The second group showed the curves which were markedly different in the presence and absence of Ca2+. 3) The third group had no effects on the enzyme activity. The membrane-bound guanylate cyclase activity in the erythrocyte membrane fractions was about 2 times stronger than that in the lymphocyte fractions. On the other hand, the membrane-bound guanylate cyclase activity in the erythrocyte fractions from peripheral blood was not enhanced by these substances. The marked activation of the guanylate cyclase by lysophospholipids and linoleate is considered to have important significance in the regulation of cGMP-mediated signal transduction.