Metabolic transformation of colchicine, III. Inhibition of phosphatases by the metabolite O10-demethylcolchicine (colchiceine) and their reactivation by divalent cations.
Colchicine and some of its metabolites and derivatives were investigated regarding their inhibitory action against alkaline phosphatases from E. coli and calf intestine, and against acid phosphatase from potato. Colchicine itself was essentially ineffective, also its metabolites O2-demethyl- and O3-demethylcolchicine. The metabolite O10-demethylcolchicine (= colchiceine) was found to be a powerful, non-competitive inhibitor for all three phosphatases with Ki in the range of 0.45-6.0mM. Amongst the derivatives of colchicine, colchiceyltaurine proved to be a non-competitive inhibitor of acid phosphatase (Ki=3.0mM); desacetylcolchiceine behaved like colchiceine. The inhbitory actions of colchiceine and desacetylcholchiceine could be completely reversed by the addition of Mg2, Ca2, or Zn2, respectively. This interaction with divalent cations demonstrates a novel type of action of the metabolite colchiceine when compared with its mother alkaloid and is possibly of major biological significance.