Enzymes, plant introduction

As described earlier, translation of the EPSPS mRNA of plants results in the formation of a protein which has an AJ-terminal extension. The AJ-terminal extension, referred to as the chloroplast transit peptide, is necessary and sufficient for the import of the preprotein by the chloroplast. Once imported by the chloroplast, the transit peptide is cleaved releasing the mature enzyme. As expected, introduction of the EPSPS transit peptide to other protein sequences results in the importation of the fusion protein by the chloroplast. 

All of the transformations illustrated in Scheme 1 are oxidative in nature and are typical of reactions catalyzed by well-known enzyme systems found in microorganisms, plants, and mammals. Monooxygenase activation and introduction of molecular oxygen may result in the formation of carbinolamine 2, which... 

The simplest case to consider would be one where a plant had been genetically modified to make a new protein, a protein without enzyme activity, such as the introduction of the Bt toxin. In this case, the concept of equivalence is typically applied. The case is made that the chemistry of the unmodified plant and modified plant are likely to be so similar that they can be considered to be equivalent. 

Highly toxic groups will be found. They may be used to step up old nematocides or bring new ones to the fore. However, soil nematocides are contact killers and as such will be supplanted by chemotherapy. Plants will be fed materials toxic to the nematode. Such chemicals (stomach poisons) are already here, as indicated by sodium selenate. Plant parasitic nematodes can bathe in it, but unless it is absorbed by the plant and thus fed to the nematode, no injury is done. The mode of action of parathion is still uncertain. Plant parasitic nematodes placed in a saturated aqueous solution certainly survive for long periods, yet it has been found effective in the control of certain nematodes in living plants 16y 0), The next step is the introduction into the plant of nutriments to replace those taken from the plant by the nematode. The final step is the introduction into the plant of neutralizers of nemic enzymes. This may have already been done in the case of parathion, for it is said to inhibit cholinesterase formation in other animals. Chemotherapy will then have its day, but when that day is done physics may be expected to take over liie burdens of the control of plant diseases. We can expect the use of ultrasonics and radioactive fertilizers. 

There is thus some evidence for the tight binding of enzymes, especially glycosidases, to cell walls in both dicots and monocots. The nature and localization of these enzymes suggest that they may, perhaps, play a role in wall breakdown and such other processes as elongation growth. The membrane systems of plant cells are known to be involved in the transport, and introduction, of polysaccharides into the cell wall247-249 enzymes localized in the wall may also play a part in the metabolism of these polymers when they are transferred from the membrane system to the wall. 

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