Topoisomerases IB are anticancer and antimicrobial targets whose inhibition by several natural and non-natural compounds has been documented. The inhibition effect by berberine and some 13-(di)phenylalkyl berberine derivatives has been tested towards human topoisomerase IB. Derivatives belonging to the 13-diphenylalkyl series display an efficient inhibition of the DNA relaxation and cleavage step, that increases upon pre-incubation with the enzyme. The religation step of the enzyme catalytic cycle is not affected by compounds and only slightly upon pre-incubation. The binding of the protein to the DNA substrate occurs also in the presence of the compounds, as monitored by a DNA shift assay, indicating that the compounds are not able to inhibit the formation of the enzyme-DNA complex but that they act as catalytic inhibitors.
Keywords: Berberine chloride; Human topoisomerase IB; Natural compound.
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