Organic food quality: from field to fork

Abstract

UDP‐galactose mutase is a flavoenzyme that catalyzes the isomerization of UDP‐galactopyranose into UDP‐galactofuranose, a key step in the biosynthesis of important bacterial oligosaccharides. Several mechanisms for this unique ring‐contraction have been proposed, one of them involving a putative 1,4‐anhydrogalactopyranose as an intermediate in the reaction. The purpose of this study was to probe the mutase binding site with conformationally restricted analogues of its substrate. Thus, we describe the straightforward synthesis of two C‐glycosidic UDP‐galactose derivatives: analogue 1, presenting a galactose moiety locked in a bicyclic 1,4B boat conformation, and UDP‐C‐Galf 2, where the galactose residue is locked in the conformation of the mutase substrate. The two molecules were found to be inhibitors of UDP‐galactose mutase at levels depending on the redox state of the enzyme. Strong inhibition of the native enzyme, but a low one of the reduced mutase, were observed with UDP‐C‐Galf 2, whereas 1 displayed intermediate inhibition levels under both native and reducing conditions. These data provide evidence of a significant conformational difference of the mutase binding pocket in the reduced enzyme and in the native one, the enzyme switching from a low Galf‐affinity state (reduced enzyme) to a very strong one (native enzyme). It is remarkable that the mutase binds the boat‐locked analogue 1 with similar affinities in both its conformational states. These results support a mechanism involving the formation of 1,4‐anhydrogalactopyranose as a low‐energy intermediate. An alternative explanation would be that the distortion of the galactose moiety during the cycle contraction transiently brings the carbohydrate into a conformation close to a 1,4B boat.

Organic Agriculture 3.0 is innovation with research

“…For this reason, the organic sector must keep high quality standards and provide verifiable and realistic information about in which value-added categories organic food is supported by substantial research and in which categories the support is not (yet) evident. In addition to the authentication and regulation of farming practices, transparency on realistic organic benefits will safeguard organic integrity throughout the supply and consumption chain (Kahl 2012).…”

“…One of the major challenges for the organic agri-food system is to change the fieldwork-driven Organic 2.0 groundwork to an Organic 3.0 methodology that uses information from a broad sector of conducted research, consumer interest and sustainable consumption as a driver of organic growth (weeding) (Kahl et al 2010;Kahl 2012). Organic 3.0 will include information on value-added components of organic food and farming and will be supported by the rapid increase in data available to perform meta-analyses comparing levels of relevant compounds in organic and non-organic products (e.g.…”

The measurement of competitiveness of forest green food industry in Yunnan Province

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Research on organic food quality needs a system approach

“…After the great success of the first event on this topic in Prague 2011, where the different research questions and approaches on organic food quality research were brought together (see the Special Issue published in JSFA in 2012 ), the second event marked a new step towards identified major research goals.…”