A comparative study of the synthesis of 3-substituted catechols using an enzymatic and a chemoenzymatic method

A series of cis-dihydrodiol metabolites, available from the bacterial dioxygenase-catalysed oxidation of monosubstituted benzene substrates using Pseudomonas putida UV4, have been converted to the corresponding catechols using both a heterogeneous catalyst (Pd/C) and a naphthalene cis-diol dehydrogenase enzyme present in whole cells of the recombinant strain Escherichia coli DH5 alpha(pUC129: nar B). A comparative study of the merits of both routes to 3-substituted catechols has been carried out and the two methods have been found to be complementary. A similarity in mechanism for catechol formation under both enzymatic and chemoenzymatic conditions, involving regioselective oxidation of the hydroxyl group at C-1, has been found using deuterium labelled toluene cis-dihydrodiols. The potential, of combining a biocatalytic step (dioxygenase-catalysed cis-dihydroxylation) with a chemocatalytic step (Pd/C-catalysed dehydrogenation), into a one-pot route to catechols, from the parent substituted benzene substrates, has been realised.

SOCS3 Targets Siglec 7 for Proteasomal Degradation and Blocks Siglec 7-mediated Responses

CD33-related Siglecs (sialic acid-binding immunoglobulin-like lectins) 5–11 are inhibitory receptors that contain a membrane proximal ITIM (immunoreceptor tyrosine-based inhibitory motif) (I/V/L/)XYXX(L/V), which can recruit SHP-1/2. However, little is known about the regulation of these receptors. SOCS3 (suppressor of cytokine signaling 3) is up-regulated during inflammation and competes with SHP-1/2 for binding to ITIM-like motifs on various cytokine receptors resulting in inhibition of signaling. We show that SOCS3 binds the phosphorylated ITIM of Siglec 7 and targets it for proteasomal-mediated degradation, suggesting that Siglec 7 is a novel SOCS target. Following ligation, the ECS E3 ligase is recruited by SOCS3 to target Siglec 7 for proteasomal degradation, and SOCS3 expression is decreased concomitantly. In addition, we found that SOCS3 expression blocks Siglec 7-mediated inhibition of cytokine-induced proliferation. This is the first time that a SOCS target has been reported to degrade simultaneously with the SOCS protein and that inhibitory receptors have been shown to be degraded in this way. This may be a mechanism by which the inflammatory response is potentiated during infection.