Lactic acid, a central metabolic intermediate of many cells, occurs as L- and D-isomers that are interconverted by lactate racemase. This enzyme from Lactobacillus plantarum is encoded by LarA and harbors a tethered nickel-pincer nucleotide (NPN) coenzyme derived from niacin. Synthesis of the enzyme-bound cofactor requires LarB, a carboxylase/hydrolase of nicotinic acid adenine dinucleotide (NaAD); LarE, a Mg·ATP-dependent sacrificial sulfur insertase; and LarC, a CTP-dependent nickel insertase or cyclometallase. This seminar will summarize recent studies related to NPN synthesis and function.
Desguin B, T. Zhang, P. Soumillion, P. Hols, J. Hu, and R. P. Hausinger (2015) A tethered niacin-derived pincer complex with a nickel-carbon bond in lactate racemase. Science 349(6243):66–69.
Rankin, J. A., R. C. Mauban, M. Fellner, B. Desguin, J. McCracken, J. Hu, S. A. Varganov, and R. P. Hausinger. 2018. Lactate racemase nickel-pincer cofactor operates by a proton-coupled hydride transfer mechanism. Biochemistry 57:3244-3251.
Hausinger, R. P., B. Desguin, M. Fellner, J. A. Rankin, and J. Hu. 2018. Nickel-pincer nucleotide cofactor. Curr. Opin. Chem. Biol. 47:18-23.
Hausinger, R. P. 2019. New metal cofactors and recent metallocofactor insights. Curr. Opin. Struct. Biol. 59:1-8.