The efficacy of β-lactam antibiotics is threatened by the emergence and global spread of metallo-β-lactamase-(MBL) mediated resistance, specifically New Delhi-Metallo-β-lactamase-1 (NDM-1). Utilizing fragment-based drug discovery (FBDD), a new class of inhibitors for NDM-1 and two related β-lactamases, IMP-1 and VIM-2, was identified. Based on 2,6-dipicolinic acid (DPA), several libraries were synthesized for structure-activity relationship (SAR) analysis. Inhibitor 36 (IC50 = 80 nM) was identified to be highly selective for MBLs when compared to other Zn(II) metalloenzymes. While DPA displayed a propensity to chelate metal ions from NDM-1, 36 formed a stable NDM-1:Zn(II):inhibitor ternary complex, as demonstrated by 1H NMR, electron paramagnetic resonance (EPR) spectroscopy, equilibrium dialysis, intrinsic tryptophan fluorescence emission, and UV-Vis spectroscopy. When co-administered with 36 (at concentrations non-toxic to mammalian cells), the minimum inhibitory concentration (MIC) of imipenem against clinical isolates of Eschericia coli and Klebsiella pneumoniae harboring NDM-1 were reduced to susceptible levels.

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Adaptive thermogenesis has attracted much attention because of its ability to raise systemic energy expenditure and counter obesity and diabetes 1,2,3 . Recent data have indicated that thermogenic fat cells utilize creatine to stimulate futile substrate cycling, dissipating chemical energy as heat 4,5 . This model was based on the super-stoichiometric relationship between creatine added to mitochondria and O 2 consumed. Here we provide direct evidence for the molecular basis of this futile creatine cycling (FCC) activity. Thermogenic fat cells contain robust phosphocreatine phosphatase activity, attributable to tissue-nonspecific alkaline phosphatase (TNAP). TNAP hydrolyzes phosphocreatine to initiate a futile cycle of creatine dephosphorylation and phosphorylation. Remarkably, unlike in other cells, TNAP is localized to mitochondria of thermogenic fat cells, where FCC occurs. TNAP expression is powerfully induced when animals are subjected to cold exposure. Moreover, the essential role of TNAP in the FCC is illustrated by the loss of this cycle when TNAP is inhibited in isolated mitochondria. Finally, genetic ablation of TNAP in adipocytes reduces whole body energy expenditure and causes rapid-onset obesity, with Reprints and permissions information is available at www.nature.com/reprints.