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Lysine acetylation regulates many eukaryotic cellular processes, but its function in prokaryotes is largely unknown. We demonstrated that central metabolism enzymes in Salmonella were acetylated extensively and differentially in response to different carbon sources, concomitantly with changes in cell growth and metabolic flux. The relative activities of key enzymes controlling the direction of glycolysis versus gluconeogenesis and the branching between citrate cycle and glyoxylate bypass were all regulated by acetylation. This modulation is mainly controlled by a pair of lysine acetyltransferase and deacetylase, whose expressions are coordinated with growth status. Reversible acetylation of metabolic enzymes ensure that cells respond environmental changes via promptly sensing cellular energy status and flexibly altering reaction rates or directions. It represents a metabolic regulatory mechanism conserved from bacteria to mammals. 10.1126/science.1179687

The binuclear copper enzyme tyrosinase activates [O.sub.2] to form a μ-[η.sup.2]:[η.sup.2]-peroxodicopper(II) complex, which oxidizes phenols to catechols. Here, a synthetic μ-[η.sup.2]:[η.sup.2]-peroxodicopper(II) complex, with an absorption spectrum similar to that of the enzymatic active oxidant, is reported to rapidly hydroxylate phenolates at -80°C. Upon phenolate addition at extreme temperature in solution (-120°C), a reactive intermediate consistent with a bis-μ-oxodicopper(III)-phenolate complex, with the O-O bond fully cleaved, is observed experimentally. The subsequent hydroxy[ation step has the hallmarks of an electrophilic aromatic substitution mechanism, similar to tyrosinase. Overall, the evidence for sequential O-O bond cleavage and C-O bond formation in this synthetic complex suggests an alternative intimate mechanism to the concerted or late stage O-O bond scission generally accepted for the phenol hydroxylation reaction performed by tyrosinase., Tyrosinase is a ubiquitous binuclear copper enzyme, found in fungi, plants, and animals, that catatyzes the hydroxylation of phenots to catechols and the oxidation of catechols to quinones (1). The [...]