Mn2+-Dependent L-Ascorbate 6-Phosphate Lactonase
Published Online: 15 JUN 2012
Copyright © 2011 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Inorganic and Bioinorganic Chemistry
How to Cite
Fernandez, F. J. and Vega, M. C. 2012. Mn2+-Dependent L-Ascorbate 6-Phosphate Lactonase. Encyclopedia of Inorganic and Bioinorganic Chemistry. .
- Published Online: 15 JUN 2012
This enzyme (UlaG) catalyzes the first catabolic reaction in the ascorbate assimilation pathway, the divalent-metal-dependent hydrolytic lactone ring opening of l-ascorbate 6-phosphate into 3-keto-l-gulonate 6-phosphate. Apart from its physiologic reaction, UlaG can also cleave phosphodiester bond linkages within substrates such as cyclic nucleoside monophosphates and phosphatase-type substrates [e.g., bis(p-nitrophenylphosphate), bis-pNPP]. The crystal structures of the UlaG apoenzyme and the Mn2+ holoenzyme have revealed a novel structural paradigm for an entire new family of MBL like metalloenzymes, characterized by an RNase Z-reminiscent fold, an intricate hexameric arrangement, and a mononuclear or dinuclear metal site. This hexameric enzyme is absolutely dependent on Mn2+ or Co2+ for activity and becomes severely inhibited by Zn2+. Phylogenetic analyses show that present-day UlaG may have originated by gene duplication from an ancestral RNA-metabolizing template and evolved through extensive neofunctionalization to acquire sugar-phosphate hydrolytic activity.
- l-ascorbate metabolism;