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Numerous carbohydrate-processing enzymes facilitate catalysis via stabilization of positive charges near the C1, C4, C5 or C6 positions, but reactions catalyzed by these enzymes are diverse. An easy method that allows easy access to different varieties of 5-fluoro group glycosides as well as glycosyl phosphates is developed with the aim to solve the difficulties faced in introducing the 5-fluoro substituent after radical halogenation.

A four-dimensional (4-D) nuclear magnetic resonance (NMR) study of Escherichia coli-malate synthase G (MSG), a 723-residue monomeric enzyme (81.4 kDa), is described. Virtually complete backbone (super 1)HN, (super 15)N, (super 13)C, and (super 13)C(super beta) chemical shift assignments of this largely alpha-helical protein are reported, which helps in characterizing the dynamical properties of the enzyme that are likely important for function.

Structural studies of the tunnel-shaped active site of Cel6A, which is an inverting glycosidase, contains two aspartic acids, D221 and D175 and are at hydrogen-bonding distance from each other. The site-directed mutagenesis, X-ray crystallography, and enzyme kinetic studies are conducted to confirm the role of residue D221 as the catalytic acid, and it is suggested that the single-displacement mechanism of Cel6A may not directly involve a catalytic base.

The Strecker reaction, the hydrocynation of imines is one of the most widely studied reactions especially since the structurally novel metal-free catalyst system that displays high enantioselectivity is seen in this reaction. The structural and mechanistic studies that shed light on this issue and lay the foundation for rational catalyst optimization is reported.

Phytopathogens promote virulence by, for example, exploiting signaling pathways mediated by phytohormones such as abscisic acid (ABA) and jasmonate (JA). Some plants can counteract pathogen virulence by invoking a potent form of immunity called effector-triggered immunity (ETI). Here, we report that ABA and JA mediate inactivation of the immune-associated MAP kinases (MAPKs), MPK3 and MPK6, in Arabidopsis thaliana. ABA induced expression of genes encoding the protein phosphatases 2C (PP2Cs), HAI1, HAI2, and HAI3 through ABF/AREB transcription factors. These three HAI PP2Cs interacted with MPK3 and MPK6 and were required for ABA-mediated MPK3/MPK6 inactivation and immune suppression. The bacterial pathogen Pseudomonas syringae pv. tomato (Pto) DC3000 activates ABA signaling and produces a JAmimicking phytotoxin, coronatine (COR), that promotes virulence. We found that Pto DC3000 induces HAI1 through COR-mediated activation of MYC2, a master transcription factor in JA signaling. HAI1 dephosphorylated MPK3 and MPK6 in vitro and was necessary for COR-mediated suppression of MPK3/MPK6 activation and immunity. Intriguingly, upon ETI activation, A. thaliana plants overcame the HAI1-dependent virulence of COR by blocking JA signaling. Finally, we showed conservation of induction of HAI PP2Cs by ABA and JA in other Brassicaceae species. Taken together, these results suggest that ABA and JA signaling pathways, which are hijacked by the bacterial pathogen, converge on the HAI PP2Cs that suppress activation of the immune-associated MAPKs. Also, our data unveil interception of JA-signaling activation as a host counterstrategy against the bacterial suppression of MAPKs during ETI. [ABSTRACT FROM AUTHOR]