Characterization of neutral lipases revealed the tissue-specific triacylglycerol hydrolytic activity in Nilaparvata lugens.

The lipid metabolism plays an essential role in the development and reproduction of insects, and lipases are important enzymes in lipid metabolism. In Nilaparvata lugens, an important insect pest on rice, triacylglycerol hydrolytic activities were different among tissues, with high activity in integument, ovary, and fat body, but low activity in intestine. To figure out the tissue-specific triacylglycerol hydrolytic activity, we identified 43 lipases in N. lugens. Of these 43 lipases, 23 belonged to neutral lipases, so this group was selected to perform further experiments on triacylglycerol hydrolysis. The complete motifs of catalytic triads, ß9 loop, and lid motif, are required for the triacylglycerol hydrolytic activity in neutral lipases, which were found in some neutral lipases with high gene expression levels in integument and ovary, but not in intestine. The recombinant proteins of 3 neutral lipases with or without 3 complete motifs were obtained, and the activity determination confirmed the importance of 3 motifs. Silencing XM_022331066.1, which is highly expressed in ovary and with 3 complete motifs, significantly decreased the egg production and hatchability of N. lugens, partially through decline of the lipid metabolism. In summary, at least one-third of important motifs were incomplete in all neutral lipases with high gene expression in intestine, which could partially explain why the lipase activity in intestine was much lower than that in other tissues. The low activity to hydrolyze triacylglycerol in N. lugens intestine might be associated with its food resource and nutrient components, and the ovary-specific neutral lipases were important for N. lugens reproduction.

A three-dimensional zinc-based coordination polymer built from 5-carboxylato-1-carboxylatomethyl-2-oxidopyridinium with a 4-connected sra topology.

A novel three-dimensional Zn(II) complex, poly[aqua(µ4-5-carboxylato-1-carboxylatomethyl-2-oxidopyridinium)zinc(II)], [Zn(C8H5NO4)(H2O)]n, has been prepared by hydrothermal assembly of Zn(CH3COO)2·2H2O and 5-carboxy-1-(carboxymethyl)pyridin-1-ium-2-olate (H2ccop). The ccop(2-) anions bridge the Zn(II) cations in a head-to-tail fashion via monodentate aromatic carboxylate and phenolate O atoms to form an extended zigzag chain which runs parallel to the [011] direction. One O atom of the aliphatic carboxylate group of the ccop(2-) ligand coordinates to the Zn(II) atom of a neighbouring chain thereby producing undulating layers which lie parallel to the (01-1) plane. A similar parallel undulating planar structure can be obtained if a path involving the other O atom of the aliphatic carboxylate group is considered. Thus, the aliphatic carboxylate group acts in a bridging bidentate mode to give extended -Zn-O-C-O-Zn- sequences running parallel to [001] which link the layers into an overall three-dimensional framework. The three-dimensional framework can be simplified as a 4-connected sra topology with a Schläfli symbol of 4(2).6(3).8 if all the Zn(II) centres and ccop(2-) anions are regarded as tetrahedral 4-connected nodes. The three-dimensional luminescence spectrum was measured at room temperature with excitation and emission wavelengths of 344-354 and 360-630 nm, respectively, at intervals of 0.15 and 2 nm, respectively.