HYDROLYTIC SELECTIVITY OF PATATIN (LIPID ACYL HYDROLASE) FROM POTATO (SOLANUM TUBEROSUM L.) TUBERS TOWARD VARIOUS LIPIDS

The fatty acid and positional hydrolytic selectivity of lipid acyl hydrolase (LAH; patatin) isolated from potato tubers was determined for acylgfycerol and phospholipid substrates. LAH was about 3-fold more selective for decanoyl residues over other acyl groups of 8–18 carbons for partial glyceride substrates. For both mono- and diacylglycerols, LAH preferred substrates with primary (sn-1 (3)-) ester linkages, indicating a regiobias for these sites over sn-2-linked acyl groups. Similarly, hydrolytic activity on phospholipid substrates was 5- to 10-fold faster on sn-l-palmitoyl, sn-2-lysophospholipids than on intact phospholipids, indicating a preference for either lysophospholipids or sn-l-acyl sites, or both. LAH activity on partial glycerides was not activated by CaCl² and had a greater temperature optimum relative to LAH activity on phospholipid substrates. These differences are likely based on differences in forces and structural features conferring enzyme-substrate recognition for these substrates within a common active site.     

Robust Stabilization of Nonlinear Systems via Normalized Coprime Factor Representations

A reasonably complete theory for the synthesis of robust controllers for a broad class of nonlinear systems is now available. We use this theory to generalize the linear theory of normalized coprime factor robustness optimization to the case of affine input nonlinear systems. In particular, we show that the equilibrium controller may be characterized in terms of the stabilizing and destabilizing solutions of the Hamilton–Jacobi equation used to calculate the normalized (right) coprime factors of the plant. We also show that the optimal robustness margin of

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Abstract

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Abstract

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