Fatty acid-sensitive acid phosphatase activity of tubercle bacilli

In a whole cell assay system with p-nitrophenyl phosphate as substrate, strains of Mycobacterium tuberculosis and M. bovis were identical in the pH-activity pattern of acid phosphatase. It was a one-peak curve with a pH optimum at 6.2 and sharp symmetrical slopes. The enzymatic activity did not reflect the virulence. When the cells were subjected to mechanical fractionation, the major part of the enzymatic activity was found in a particulate fraction and a minor portion in supernatant and cell walls, suggesting the location of the enzyme in the membrane. Exposure of the cells to free long-chain fatty acids, especially unsaturated ones, reduced the enzymatic activity in a dose-response manner with concomitant decrease in the viability. However, no causal relationship between these two effects was suggested from the collateral experiments.