Inhibitors of bacterial cystathionine beta-lyase: leads for new antimicrobial agents and probes of enzyme structure and function.

Linda J Ejim, Jan E Blanchard, Kalinka P Koteva, Rachael Sumerfield, Nadine H Elowe, Jonathan D Chechetto, Eric D Brown, Murray S Junop, Gerard D Wright

Index: J. Med. Chem. 50 , 755-64, (2007)

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Abstract

The biosynthesis of methionine is an attractive antibiotic target given its importance in protein and DNA metabolism and its absence in mammals. We have performed a high-throughput screen of the methionine biosynthesis enzyme cystathionine beta-lyase (CBL) against a library of 50 000 small molecules and have identified several compounds that inhibit CBL enzyme activity in vitro. These hit molecules were of two classes: those that blocked CBL activity with mixed steady-state inhibition and those that covalently interacted with the enzyme at the active site pyridoxal phosphate cofactor with slow-binding inhibition kinetics. We determined the crystal structure of one of the slow-binding inhibitors in complex with CBL and used this structure as a guide in the synthesis of a small, focused library of analogues, some of which had improved enzyme inhibition properties. These studies provide the first lead molecules for antimicrobial agents that target cystathionine beta-lyase in methionine biosynthesis.