As Nature Catalysis starts its third year, we look back and the past 12 months.

The C-branched pentose sugar d-apiose is important for plant cell wall development. Its biosynthesis as urdine diphosphate-d-apiose (UDP-d-apiose) involves decarboxylation of the UDP-d-glucuronic acid precursor coupled with pyranosyl-to-furanosyl sugar ring contraction. This unusual multistep reaction is catalysed in a single active site by UDP-d-apiose/UDP-d-xylose synthase (UAXS). Here we decipher the UAXS catalytic mechanism on the basis of crystal structures of the enzyme (which is from Arabidopsis thaliana), molecular dynamics simulations that are expanded by hybrid quantum mechanics/molecular mechanics calculations and mutational mechanistic analyses. Our studies show how UAXS uniquely integrates a classical catalytic cycle of oxidation and reduction by a tightly bound nicotinamide co-enzyme with retroaldol/aldol chemistry for the sugar ring contraction. We further demonstrate that decarboxylation occurs only after the sugar ring opening and identify that the thiol group of Cys100 steers the sugar skeleton rearrangement by proton transfer to and from C3′. The mechanistic features of UAXS highlight the evolutionary expansion of the basic catalytic apparatus of short-chain dehydrogenases/reductases for functional versatility in sugar biosynthesis.

Bioelectrocatalysis provides access to sustainable and highly efficient technological applications. However, several limitations related either to the intrinsic properties of the biocatalyst or to technical difficulties still hamper or even prevent the integration of such devices into technologically relevant large-scale processes. In this Review, we challenge the common viewpoint suggesting biology-based catalytic systems as a promising approach for the provision of sustainable stored energy and discuss the status of bioelectrocatalytic devices developed for energy conversion. In particular, we focus on two major research areas in the field, that is, H2-powered hydrogenase-based biofuel cells and biophotoelectrodes for solar energy harvesting. We identify the main limitations that have to be addressed to gain access to applied large-scale bio-based and bio-inspired advanced energy conversion systems. Moreover, we show recent examples and milestones that are paving the way towards potential realization of these technologies by overcoming existing limiting factors.

Plastic waste is a serious matter of concern due to its disruptive impact on the environment. While disposal and reclaim strategies represent the first lines of intervention to solve this problem, upcycling options based on catalytic transformations will eventually be necessary to reconvert enormous quantities of such material.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The global average temperature has been continuously rising for over a century. Action must be taken.