Novel prenyl-linked benzophenone substrate analogues of mycobacterial mannosyltransferases.
Biochem J
; 382(Pt 3): 905-12, 2004 Sep 15.
Article
em En
| MEDLINE
| ID: mdl-15202931
ABSTRACT
PPM (polyprenol monophosphomannose) has been shown to act as a glycosyl donor in the biosynthesis of the Man (mannose)-rich mycobacterial lipoglycans LM (lipomannan) and LAM (lipoarabinomannan). The Mycobacterium tuberculosis PPM synthase (Mt-Ppm1) catalyses the transfer of Man from GDP-Man to polyprenyl phosphates. The resulting PPM then serves as a donor of Man residues leading to the formation of an alpha(1-->6)LM intermediate through a PPM-dependent alpha(1-->6)mannosyltransferase. In the present study, we prepared a series of ten novel prenyl-related photoactivatable probes based on benzophenone with lipophilic spacers replacing several internal isoprene units. These probes were excellent substrates for the recombinant PPM synthase Mt-Ppm1/D2 and, on photoactivation, several inhibited its activity in vitro. The protection of the PPM synthase activity by a 'natural' C(75) polyprenyl acceptor during phototreatment is consistent with probe-mediated photoinhibition occurring via specific covalent modification of the enzyme active site. In addition, the unique mannosylated derivatives of the photoreactive probes were all donors of Man residues, through a PPM-dependent mycobacterial alpha(1-->6)mannosyltransferase, to a synthetic Manp(1-->6)-Manp-O-C(101) disaccharide acceptor (where Manp stands for mannopyranose). Photoactivation of probe 7 led to striking-specific inhibition of the M. smegmatis alpha(1-->6)mannosyltransferase. The present study represents the first application of photoreactive probes to the study of mycobacterial glycosyltransferases involved in LM and LAM biosynthesis. These preliminary findings suggest that the probes will prove useful in investigating the polyprenyl-dependent steps of the complex biosynthetic pathways to the mycobacterial lipoglycans, aiding in the identification of novel glycosyltransferases.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fosfatos de Poli-Isoprenil
/
Proteínas de Bactérias
/
Benzofenonas
/
Marcadores de Fotoafinidade
/
Mycobacterium smegmatis
/
Manosiltransferases
/
Mycobacterium tuberculosis
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
Biochem J
Ano de publicação:
2004
Tipo de documento:
Article
País de afiliação:
Reino Unido