Enzymes defense-related

Shinshi, H., Wenzler, H., Neuhaus, J.M., Felix, G., Hofsteenge, J. Meins, F. (1988). Evidence for N- and C-terminal processing of a plant defense-related enzyme Primary structure of tobacco prepro-P-1,3-glucanase. Proceedings of the National Academy of Sciences (USA) 85, 5541-5. 

Yin, H., Zhao, X., and Du, Y.G. 2008c. Induction of some defense-related enzyme activity in response to oligochitosan in Brassica napus. Glycobiology 18 955-956. 

In the phenylpropanoid pathway, the first biosynthetic step leading to SA is a deamination of phenylalanine to CA which is catalyzed by phenylalanine ammonia lyase (PAL). This enzyme is induced by a range of biotic and abiotic stress conditions and is a key regulator in the phenylpropanoid pathway, which yields a variety of phenolics among others involved in structural and defense-related functions [42]. In recent years, PAL and its corresponding genes have been subject of numerous studies in various plant species [43 7]. 

Moreover, AMF may represent underground communication ways [106], also activating defense pathways before the pathogen attacks. For example, tomato plants colonized by the same AM symbiont showed increased expressimi of defense-related genes and higher levels of disease resistance enzymes in healthy receiver plants after inoculation of donor plants with a pathogen [107]. 

A key question is the extent to which any of these in vitro biochemical studies are useful for in predicting the respective GT activity and physiological functions in planta. Thus, in vivo factors which can influence GT activity in plant cells, such as cofactors, protein-protein interactions and metabolite channelling are absent in the in vitro assays. It is thus essential to examine the functional activity of GTs by altering their expression in planta, when probing the roles of these enzymes in development, metabolic or stress/defense-related pathways. 

Kim HY, Shin HY, Sohn DS, Lee IJ, Kim KU, Lee SC, Jeong HJ, Cho MS (2000) Enzyme activities and compounds related to self-defense in UV-challenged leaves of rice. Korean J Crop Sci 46 22-28... 

Little information about the mechanism of action of flavonoids is anticipated from in vivo studies. The mechanism of catechin and morin seems to be related to an increase of the activity of detoxifying enzymes like glutathione-S-transferase and NADPH quinone reductase [198, 211]. Similarly, EGCG effect at the colonic level is associated to an increase in tissue superoxide dismutase levels, suggesting that it may act through a potentiation of the antioxidative defense [210]. 

Tiedge, M., Lortz, S., Drinkgern, J. and Lenzen, S. (1997). Relation between antioxidant enzyme gene expression and antioxidative defense status of insulin-producing cells. Diabetes 46, 1733-1742. 

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