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When Tetrahymena thermophila was incubated with taurolipid A isolated from T. pyriformis NT-1, the exogenously added taurolipid A was deacylated rapidly, and taurolipid B content in the cells was increased. The deacylated taurolipid A (lysotaurolipid A) content reached a maximum early on during incubation, and then declined. Taurolipid B and lysotaurolipid B contents in the cells were increased continuously during the incubation. These observations suggest that lysotaurolipid A was an intermediate for taurolipid B formation. When cells were incubated with lysotaurolipid A, newly formed lysotaurolipid B and taurolipid B were observed. Furthermore, when cells were incubated with lysotaurolipid B, only taurolipid B was newly formed. In contrast, newly formed lysotaurolipid B was observed when cells were incubated with exogenous taurolipid B. From the results, we have postulated the biosynthetic pathway of taurolipid B from exogenous taurolipid A in cells of Thermophila.

The second taurine-containing lipid (taurolipid B) was found in cells of Tetrahymena thermophila . The lipid accounted for about 1.4% of the total lipids of the cells. The lipid was subjected to mild alkaline and methanolic hydrochloric acid hydrolyses, and the structures of the hydrolysis products were identified by mass and nuclear magnetic resonance spectrometry, as taurine, 2,3,7,13- tetrahydroxystearic acid and non-hydroxy fatty acids. By spin-decoupling analysis in nuclear magnetic resonance spectrometry, the structure of the taurolipid B was identified as 2-(3-acyloxy-2,7,13-trihydroxyoctadecanoyl)aminoethane-sulfonic acid. This structure shows that taurolipid B is a homologue of the first taurine-containing lipid (taurolipid A).

Effects of novel taurolipid A and B localized in Tetrahymena lysosomes on the activities of lysosomal enzymes purified from Tetrahymena were investigated. Both taurolipids activated acid phosphatase, while they did not affect α-glucosidase and β-hexosaminidase. The acid phosphatase activity was activated approximately 3-fold by both taurolipids A and B, with the half-maximum activations for taurolipid A and B being at approximately 1.03·10 −4 and 0.72·10 −4 M, respectively. When the purified acid phosphatase was incubated at 37°C in citrate-phosphate buffer (pH 5.0) its activity was rapidly inactivated, but the inactivation was prevented to a remarkable extent by the addition of taurolipids to the incubation medium. These results thus suggest that the taurolipids may be involved in activating and stabilizing acid phosphatase in Tetrahymena lysosomes.