| Abstract: | Guinea pig and human liver homogenates transformed leukotriene A4 into leukotriene B4. In both species, the enzymatic activity was recovered in the 105000 X g supernatant, and it was found to be susceptible to heat treatment (56 degrees C, 1 h). Digestion with a proteolytic enzyme also resulted in loss of enzymatic activity. The formation of leukotriene B4 was pH-dependent, with an optimum between pH 7 and pH 8.5. In addition, two other organs from the guinea-pig, lungs and kidneys, contained leukotriene A4-hydrolase activity. The identity of leukotriene B4 was ascertained by high-performance liquid chromatography, ultraviolet spectrometry, gas chromatography-mass spectrometry and bioassay. We have recently demonstrated the presence of leukotriene A4-hydrolase activity in mammalian plasma (Fitzpatrick et al. (1983) Proc. Natl. Acad. Sci. USA 80, 5425-5429). The results of the present study suggest several possible origins of this plasma leukotriene A4 hydrolase. |
