Lipase activity of guinea pig peritoneal macrophages and mycobacterial lipase inhibitor.

The interaction of mycobacterial lipase inhibitor (MLI), isolated from culture supernatant fluid of Mycobacterium tuberculosis strain H37Rv, and lipase from guinea pig peritoneal macrophages (GP-PM¢s) was investigated fluorimetrically by the modified lipase assay system which had previously been proposed. Two peaks of lipase activity were observed in the enzyme preparation from GPPM¢s. The activity of MLI against lipase from GP-PM¢s was significantly high at acidic pH less than 5. 0, and the pattern of inhibition was non-competitive. Two types of lipase were isolated from the enzyme solution prepared from GPPM¢s by an ion-exchange chromatography on a DEAE-Sepharose column. One of these acted only at pH 4. 5 and was considered to be a lysosomal acid lipase, but another showed the activity at both pH 4. 5 and 7. 0. The fomer was four times more sensitive to the activity of MLI than the latter as well as the crude enzyme preparation. the method described previously3l. 267