Ethylene releasing enzyme

Employing the compressibility principle whereby hydrostatic pressure selectively ejects integral membrane protein (including the putative ethylene-forming enzyme and/or ethylene receptor) from fluid phospholipid domains, isolated liquid crystalline pea foliage microsomal membranes were subjected to 1500 bar pressurization in a French Press for 20 min in the presence or absence of 10 ppm indoleacetic acid (lAA). Ethylene production of the protein-depleted membranes was compared to that of non-pressurized membranes. Ca release to the supernatant after pressurization was determined with tetramurexide. 

The main advantage is that the entrapment conditions are dictated by the entrapped enzymes, but not the process. This includes such important denaturing factors as the solution pH, the temperature and the organic solvent released in the course of precursor hydrolysis. The immobilization by THEOS is performed at a pH and temperature that are optimal for encapsulated biomaterial [55,56]. The jellification processes are accomplished by the separation of ethylene glycol that possesses improved biocompatibility in comparison with alcohols. 

Modifications designed to enhance the enzyme resistance and prolong the activity of SS derivatives have been quite successful. The use of D-amino acids instead of the normal L-enantiomers (e.g., in Trp ), or replacement of the disulfide link by a nonreducible ethylene bridge, leads to an increased duration of activity, approaching 3 hours. Several analogs show a greatly increased effect, like the [D-Ala, D-Trp ]somatostatin, which has 20 times the activity of SS on growth hormone release. The NH-terminal outside the cyclic dodecapeptide is not essential for activity. Selectivity of action results from... 

Dolch and Tscharntke (2000) studied the effects of artificial defoliation of alder trees on subsequent herbivory by alder leaf beetle (Agelastica alni). After defoliation, herbivory by A. alni was significantly lower in the defoliated trees and its neighbors compared with trees distant from the manipulated trees. Laboratory studies confirmed that resistance was induced not only in defoliated alders but also in their undamaged neighbors (Dolch and Tscharntke, 2000). Follow-up work showed that alder leaves respond to herbivory by A. alni with the release of ethylene and of a blend of volatile mono-, sesqui-, and homoterpenes. This herbivory also increased the activity of oxidative enzymes and proteinase inhibitors (Tscharntke et al., 2001). 

The electrochemical transformation of a molybdenum nitrosyl complex [Mo(NO)(dttd)J [dttd = 1,2-bis(2-mercaptophenylthio)ethane] (30) is rather interesting (119). Ethylene is released from the backbone of the sulfur ligand upon electrochemical reduction. The resulting nitrosyl bis(dithiolene) complex reacts with O2 to give free nitrite and a Mo-oxo complex. Multielectron reduction of 30 in the presence of protons releases ethylene and the NO bond is cleaved, forming ammonia and a Mo-oxo complex (Scheme 15). The proposed reaction mechanism involves successive proton-coupled electron-transfer steps reminiscent of schemes proposed for Mo enzymes (120). 

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