Inhibition of 7,8-diaminopelargonic acid aminotransferase by amiclenomycin and analogues

Abstract

Cis and trans stereoisomers of amiclenomycin, a natural L-amino acid antibiotic, have been prepared using unequivocal routes. By using 1H NMR spectroscopy, the configuration of the six-membered ring of natural amiclenomycin was shown to be cis and not trans as originally proposed. Amiclenomycin and some synthetic analogues with the cis configuration irreversibly inactivate DAPA AT (7,8-diaminopelargonic acid aminotransferase), an enzyme involved in biotin biosynthesis, by forming an aromatic PLP (pyridoxal-5′-phosphate)–inhibitor adduct that is tightly bound to the active site. The following kinetic parameters for the inactivation of Escherichia coli DAPA AT by amiclenomycin were derived: KI=2 μM and kinact=0.4 min−1. The structure of the aromatic adduct formed upon inactivation was confirmed by UV–visible spectroscopy, X-ray crystal structure determination and MS. Because Mycobacterium tuberculosis DAPA AT is a potential drug target, this enzyme was cloned, overexpressed and purified to homogeneity for biochemical characterization.