Axenic incorporation of [U-14C]palmitic acid into the phenolic glycolipid-I of Mycobacterium leprae

Franzblau, S

doi:10.1016/0378-1097(87)90084-x

Cited by 5 publications

(6 citation statements)

References 5 publications

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“…[14C]palmitate (a 16-carbon fatty acid) is incorporated into phenolic glycolipid I (PGL-I) (a characteristic capsular lipid [7]), is catabolized to 14CO2 (6,31), and is elongated to longer-chain fatty acids (32). Therefore, in the present work, the first study of phospholipase activity in M. leprae, the phospholipases sought are those which hydrolyze the ester bond between the glycerol and fatty acyl moiety of phospholipids to release fatty acids (Fig.…”

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confidence: 99%

Phospholipase activity of Mycobacterium leprae harvested from experimentally infected armadillo tissue

Wheeler

Ratledge

1991

Infect Immun

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Three types of phospholipase activity--phospholipase A1, A2, and lysophospholipase--were detected in Mycobacterium leprae harvested from armadillo tissue at about 25% of the specific activity found in a slowly growing mycobacterium, Mycobacterium microti, which was grown in medium to optimize its phospholipase activity. The highest activity found was lysophospholipase, which released fatty acid from 2-lyso-phosphatidylcholine. Phospholipase activity was detected by using phosphatidylcholine and phosphatidylethanolamine. Differences in relative activities with these three types of substrate distinguished phospholipase activity in M. leprae extracts from armadillo liver extracts. Furthermore, retention of activity in M. leprae after NaOH treatment showed that the activity associated with M. leprae was not host derived. The specific activity of phospholipase was 20 times higher in extracts of M. leprae than in intact M. leprae organisms. Diazotization, a treatment which abolishes activities of surface enzymes exposed to the environment by the formation of covalent azide bonds with exposed amino groups, did not affect M. leprae's phospholipase activity, with one exception: release of arachidonic acid from phosphatidylcholine, which was partially inhibited. Phenolic glycolipid I, the major excreted amphipathic lipid of M. leprae, inhibited phospholipase activity, including release of arachidonic acid, for both M. leprae- and armadillo-derived activity.

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confidence: 99%

Phospholipase activity of Mycobacterium leprae harvested from experimentally infected armadillo tissue

Wheeler

Ratledge

1991

Infect Immun

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“…Therefore, a number of in vitro systems have been developed which rely on the inhibition of metabolic activity as an indicator of drug activity (8,10,11,13,14,17,19,25). We have demonstrated the potent direct activity of erythromycin against M. leprae as determined by measurement of intracellular ATP (11), radiorespirometric assay of palmitate oxidation (8), and measurement of the rate of phenolic glycolipid I synthesis (E. B. Harris, S. G. Franzblau, and R. C. Hastings, Int.…”

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confidence: 99%

In vitro and in vivo activities of macrolides against Mycobacterium leprae

Franzblau

Hastings

1988

Antimicrob Agents Chemother

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We previously demonstrated the potent in vitro activity of erythromycin against Mycobacterium leprae as determined by its effect on ATP pools and rates of palmitate oxidation and phenolic glycolipid I synthesis. In the present study, the relative in vitro activities of a number of new macrolides with superior pharmacokinetic properties were assessed. In addition, for the most active compounds, concentrations in serum were determined by bioassay during continuous administration in the feed of mice, and in vivo activity against M. leprae was assessed by the kinetic mouse footpad technique. Both clarithromycin and roxithromycin were more potent than erythromycin in vitro, with the former showing the highest activity in accelerating rates of ATP decay and reducing rates of palmitate oxidation. In mice, concentrations of clarithromycin in serum were higher than those of roxithromycin and erythromycin, with the latter undetectable even when administered at 0.1% (wt/wt) in the diet. When administered at 0.01% (wt/wt) in the diet, erythromycin and roxithromycin were unable to inhibit growth of M. leprae in mouse footpads whereas clarithromycin demonstrated bactericidal-type activity. On the basis of these data and other properties of macrolides, a clinical trial of clarithromycin in leprosy is warranted.The existing armamentarium of antileprosy drugs is limited in number, and only one, rifampin, is rapidly bactericidal. In addition, drug-resistant strains of Mycobacterium leprae have been reported to the most commonly used agents (15). These factors among others have led to an ongoing search for new antileprosy agents.Because of the inability to cultivate the leprosy bacillus, primary drug screening has relied on the use of the mouse footpad system (MFP), which has, because of cost, time requirement, need for relatively large amounts of test drug, and necessity for favorable pharmacokinetic properties in mice, limited the number of drugs that can be evaluated. Therefore, a number of in vitro systems have been developed which rely on the inhibition of metabolic activity as an indicator of drug activity (8,10,11,13,14,17,19,25). We have demonstrated the potent direct activity of erythromycin against M. leprae as determined by measurement of intracellular ATP (11), radiorespirometric assay of palmitate oxidation (8), and measurement of the rate of phenolic glycolipid I synthesis (E. B. Harris, S. G. Franzblau, and R. C. Hastings, Int. J. Lepr., in press). We hypothesized that the failure of erythromycin to inhibit growth in the MFP (R. Gelber, personal communication) may be due to poor pharmacokinetics when the drug is administered in the feed of mice. Recently, a number of semisynthetic macrolides which have superior acid stability and serum half-lives compared with erythromycin have been developed (2,3,6,7,24). In this paper, we assess the in vitro and in vivo activities of some of these compounds against the leprosy bacillus. MATERIALS AND METHODSInoculum preparation. M. Ieprae suspensions were prepared from the footpad...

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“…To our knowledge, this study, along with our previous report (11), represents the first determination of biophysical optima for any metabolic activity of M. leprae. ATP concentration is generally considered to be a good index of overall metabolic status.…”

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confidence: 63%

Biophysical optima for metabolism of Mycobacterium leprae

Franzblau

Harris

1988

J Clin Microbiol

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The metabolic response of freshly harvested, nude-mouse-derived Mycobacterium leprae to biophysical parameters was studied to facilitate an understanding of axenic culture requirements. Quantitation of intracellular ATP and the rate of [U-14C]palmitic acid incorporation into phenolic glycolipid I (PGL-I) were used as metabolic indicators after axenic incubation in modified Dubos medium under various biophysical conditions. PGL-I synthesis was optimal at 33°C, whereas ATP was optimally maintained at .330C. Both metabolic indices showed sharp reductions at 37°C. After 5 days of incubation, PGL-I synthesis and ATP maintenance showed pH optima of 5.1 to 5.6, with the higher value appearing optimal for ATP maintenance after extended incubation. Metabolic activity was negatively affected by strong reducing agents, and ATP maintenance was optimal when the gaseous environment was maintained at 2.5 to 10% oxygen. The results may partially explain the failure to cultivate the leprosy bacillus in vitro.

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Axenic incorporation of [U-14C]palmitic acid into the phenolic glycolipid-I of Mycobacterium leprae

Cited by 5 publications

References 5 publications

Phospholipase activity of Mycobacterium leprae harvested from experimentally infected armadillo tissue

Phospholipase activity of Mycobacterium leprae harvested from experimentally infected armadillo tissue

In vitro and in vivo activities of macrolides against Mycobacterium leprae

Biophysical optima for metabolism of Mycobacterium leprae

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