Inhibition of 7,8-diaminopelargonic acid aminotransferase from Mycobacterium tuberculosis by chiral and achiral anologs of its substrate: biological implications.
7,8-Diaminopelargonic acid aminotransferase (DAPA AT), a potential drug target in Mycobacterium tuberculosis, transforms 8-amino-7-oxononanoic acid (KAPA) into DAPA. We have designed an analytical method to measure the enantiomeric excess of KAPA, based on the derivatization of its amine function, by ortho-phtalaldehyde and N-acetyl-l-cysteine, followed by high pressure liquid chromatography separation. Using this methodology and enantiopure samples of KAPA it appeared that racemization of KAPA occurs rapidly (half-lives from 1 to 8 h) not only in 4 M HCl but more importantly in the usual pH range, from 7 to 9. Furthermore, we showed that racemic KAPA, and not enantiopure KAPA, was used in all previous studies. The only valid enantioselective synthesis of KAPA is that reported by Lucet et al. (1996) Tetrahedron: Asymmetry 7, 985-988. KAPA is produced as a pure (S)-enantiomer by KAPA synthase and by microbial production and DAPA AT only uses (S)-KAPA as substrate. However, (R)-KAPA is an inhibitor of this enzyme. It binds to the pyridoxal 5'-phosphate form (K(i1) = 5.9 +/- 0.2 microM) and to the pyridoxamine 5'-phosphate form (K(i2) = 1.7 +/- 0.2 microM) of M. tuberculosis DAPA AT. Molecular modeling showed that (R)-KAPA forms specific hydrogen bonds with T309 and the phosphate group of the cofactor of DAPA AT. Desmethyl-KAPA (8-amino-7-oxooctanoic acid), an achiral analog of KAPA, is also a potent inhibitor of M. tuberculosis DAPA AT. This molecule binds to the enzyme in a similar way than (R)-KAPA with the following constants: K(i1) = 4.2 +/- 0.2 microM, and K(i2) = 0.9 +/- 0.2 microM. These findings pave the way to the design of new antimycobacterial drugs.
Biochimie des microorganismes, UMR 7223, ENSCP, Paris, France.
Stéphane
S
Mann
Lionel
L
Colliandre
Gilles
G
Labesse
Olivier
O
Ploux
D000217:Acyltransferases / Q000737:chemistry; D000596:Amino Acids / Q000737:chemistry* / Q000494:pharmacology; D000599:Amino Acids, Diamino / Q000737:chemistry; D000995:Antitubercular Agents / Q000737:chemistry* / Q000494:pharmacology; D001710:Biotin / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D013379:Substrate Specificity; D000637:Transaminases / Q000037:antagonists & inhibitors*
C542925:8-amino-7-oxooctanoic acid; D000596:Amino Acids; D000599:Amino Acids, Diamino; D000995:Antitubercular Agents; D004791:Enzyme Inhibitors; C004720:7,8-diaminopelargonic acid; C001502:7-keto-8-aminopelargonic acid; D001710:Biotin; D000217:Acyltransferases; C021929:8-amino-7-oxononanoate synthase; C020029:7,8-diaminopelargonic acid aminotransferase; D000637:Transaminases