An aldo-keto reductase with 2-keto-l-gulonate reductase activity functions in l-tartaric acid biosynthesis from vitamin C in Vitis vinifera

作者：Yong Jia, Crista A. Burbidge, Crystal Sweetman, Emi Kaye Schutz, Kathleen L. Soole, Colin L. D. Jenkins, Robert D. Hancock, John B. Bruning, Christopher M. Ford · 发表于：Journal of Biological Chemistry · 年份：2019 · DOI：10.1074/jbc.ra119.010196 · 被引用次数：29 · 研究领域：Microbial metabolism and enzyme function、Enzyme Structure and Function、Aldose Reductase and Taurine

Tartaric acid has high economic value as an antioxidant and flavorant in food and wine industries. l-Tartaric acid biosynthesis in wine grape ( Vitis vinifera ) uses ascorbic acid (vitamin C) as precursor, representing an unusual metabolic fate for ascorbic acid degradation. Reduction of the ascorbate breakdown product 2-keto-l-gulonic acid to l-idonic acid constitutes a critical step in this l-tartaric acid biosynthetic pathway. However, the underlying enzymatic mechanisms remain obscure. Here, we identified a V. vinifera aldo-keto reductase, Vv2KGR, with 2-keto-l-gulonic acid reductase activity. Vv2KGR belongs to the d-isomer–specific 2-hydroxyacid dehydrogenase superfamily and displayed the highest similarity to the hydroxyl pyruvate reductase isoform 2 in Arabidopsis thaliana . Enzymatic analyses revealed that Vv2KGR efficiently reduces 2-keto-l-gulonic acid to l-idonic acid and uses NADPH as preferred coenzyme. Moreover, Vv2KGR exhibited broad substrate specificity toward glyoxylate, pyruvate, and hydroxypyruvate, having the highest catalytic efficiency for glyoxylate. We further determined the X-ray crystal structure of Vv2KGR at 1.58 Å resolution. Comparison of the Vv2KGR structure with those of d-isomer–specific 2-hydroxyacid dehydrogenases from animals and microorganisms revealed several unique structural features of this plant hydroxyl pyruvate reductase. Substrate structural analysis indicated that Vv2KGR uses two modes (A and B) to bind different substrates. 2-Ket...