OXIDATION OF INSOLUBLE PALMITIC ACID AND WATER-SOLUBLE PALMITIC ACID-METHYLATED CYCLODEXTRIN COMPLEX BY MYCOBACTERIUM-LEPRAE AND M-PHLEI

Palmitic acid could be a suitable substrate for the in vitro cultivati on of Mycobacterium leprae but being insoluble in water it cannot be u sed effectively. Recently, dimethyl-beta-cyclodextrin complexed palmit ic acid soluble in water has become available. Thus oxidation of water soluble and insoluble palmitic acid by the host-grown M. leprae and i n vitro grown M. phlei was investigated by measuring the rate of oxyge n uptake. Insoluble and soluble palmitic acid was oxidized by M. lepra e cell suspensions after a lag period of 6 and 2 h, respectively. Solu ble palmitic acid was oxidized by M. phlei without any lag period wher eas 60 min were required before insoluble palmitic acid was oxidized. The methylated-beta-cyclodextrin alone is an inert substance and it ha d no inhibitory or stimulatory effect on the oxidation of soluble palm itic acid. Oxidation of soluble palmitic acid was markedly inhibited b y some inhibitors of the respiratory chain. Results indicate that oxid ation of palmitic acid by M. leprae and M. phlei is mediated through t he electron transport chain. Compared with insoluble palmitic acid, wa ter soluble palmitic acid has many advantages. Its use is recommended for metabolic studies, as well as in culture media used for in vitro c ultivation trials of M. leprae.