Metabolic studies on mycobacteria. IV. Assay of isocitrate lyase and malate synthase activity in M. leprae.

Cell free extracts from M. tuberculosis H37 Rv, M. smegmatis armadillo derived M. leprae and normal armadillo liver homogenates were assayed for the presence of isocitrate lyase and malate synthase activity. It was observed that significant amount of isocitrate lyase and malate synthase activity was present in M. tuberculosis H37 Rv, M. smegmatis and armadillo derived M. leprae. No such activity was demonstrable in cell free extracts of normal armadillo liver. It is concluded that M. leprae like other mycobacteria has the capability to metabolise via glyoxylate bypass of TCA cycle. These findings may be relevant for understanding the energy metabolism of M. leprae under stress conditions and possibly the 'persister' stage.

Metabolic studies on mycobacteria--II. Glyoxylate by-pass (TCA cycle) enzymes of slow and fast growing mycobacteria.

Glyoxylate by-pass of tricarboxylic acid cycle (TCA) comes into prominence during survival of microorganisms under oxygen limitations and study of these enzymes may contribute to understanding of physiology of 'persisters' in various mycobacterial diseases. The enzymes of glyoxylate by-pass have been assayed in the extracts of various mycobacterial species, namely, M. tuberculosis H37Rv, M. tuberculosis H37Ra, M. flavescens, M. vaccae, M. smegmatis and Mycobacteria strain w (M.w.). M.w. has been included because of its close antigenic resemblance to M. leprae. It has been found that all of the above investigated species possess isocitrate lyase and malate synthetase, the key enzymes of glyoxylate by-pass. The presence of the enzymes is being reported for the first time in M. flavescens, M. vaccae and M.w. whereas these were earlier shown to be present in M. tuberculosis and M. smegmatis. It was also demonstrated in M.w. where acetate alone could not serve as sole source of carbon, but in the presence of glycerol stimulates the activity of glyoxylate pathway enzymes. The importance of these findings has been discussed.