Screening of inhibitors against glucose and acetate utilization in Mycobacterium

Hew, Chaw Sen (2006) Screening of inhibitors against glucose and acetate utilization in Mycobacterium. Masters thesis, Universiti Malaysia Sabah.


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Tuberculosis is an infectious disease of human that is caused by Mycobacterium tuberculosis. TB still leads in mortality rate worldwide. One of the reasons is due to the ability of M. tuberculosis to persist slow replication and produce disease when the human immune system becomes weak. During the persistent phase, fatty acid might be used as carbon source and the two pathways involved are β-oxidation and glyoxylate cycle. Therefore the enzymes, isocitrate lyase (ICL) and malate synthase (MS) in glyoxylate cycle have become new drug targets, particularly for latent infection. The focus of this study was to isolate new strains of actinomycetes from soils of Sabah. They were then screened for inhibitors against ICL and MS which were detected by growth inhibition of M. smegmatis on acetate but non-inhibition on glucose media. Three sampling sites were chosen: Long Pasia, Melalap and Lower Segama. Thirty-three soil samples were collected and eighty-nine isolates of actinomycetes were obtained using selective media. Then crude microbial extracts were made from the 89 isolates plus other crude extracts available in the laboratory (557 of actinomycetes and 163 of fungi) were screened. One Streptomyces isolate, H11383 from Melalap showed similar inhibition to H7763 (potential ICL inhibitor from previous study) with wide partial inhibition zone on acetate medium accompanied by small inner total inhibition zones on both glucose and acetate media against M. smegmatis. Thirty-five isolates of actinomycetes and one fungus showed toxicity against M. smegmatis. This study also focuses on isolation of the active fractions from inhibitory crude extract of H7763. H7763 was found to produce 2 active fractions: Org 7 and Aq 14. Org 7 can be extracted by ethyl acetate and strongly inhibited M. smegmatis when grown on glucose or acetate. Aq 14 was water soluble and gave wide partial inhibition zone only on acetate plate. Test to detect the presence of itaconic acid (a known ICL inhibitor) in H7763 was performed using HPLC analysis and no itaconic acid was detected. The ICL enzymatic assay results showed that Aq 14 did not inhibit ICL of B. stearothermophilus with the concentration 2 mg/ml but inhibited malate synthase of M. tuberculosis. Org 7 inhibited ICL of B. stearothermophilus only at high concentration, 1.7 mg/ml.

Item Type: Thesis (Masters)
Keyword: Mycobacterium tuberculosis, human immune system, disease, isocitrate lyase (ICL), malate synthase (MS), infection
Subjects: Q Science > QH Natural history > QH301-705.5 Biology (General)
Department: SCHOOL > School of Science and Technology
Date Deposited: 23 Jun 2014 13:23
Last Modified: 30 Oct 2017 09:56

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