Pathways enzymatic regulation

Ahn, K., McKinney, M., and Cravatt, B. (2008). Enzymatic pathways that regulate endocannabinoid signaling in the nervous system. Chem. Rea. 108, 1687-1707. 

In die metabolic pathway to an amino add several steps are involved. Each step is die result of an enzymatic activity. The key enzymatic activity (usually die first enzyme in the synthesis) is regulated by one of its products (usually die end product, eg die amino add). If die concentration of die amino add is too high die enzymatic activity is decreased by interaction of die inhibitor with the regulatory site of die enzyme (allosteric enzyme). This phenomenon is called feedback inhibition. 

Expression analysis using DNA microarrays analyzes only the transcriptome it should be mentioned that mRNA abundance in a cell often correlates poorly with the amount of protein synthesized (27). Important regulation takes place at the levels of translation and enzymatic activities. The only effect of a signal transduction pathway that is observed in a gene expression experiment is that at the endpoint of a given pathway. DNA microarrays currently have little value in determining post-translational modifications, which influence the diversity, affinity, function, cellular abundance, and transport of proteins. 

It is clear that, as understanding of the underlying principles of both iminium ion and enamine catalysis improves, the trae power of these cascade sequences will be fully exploited. It can be expected that introduction of subsequent independent catalytic cycles will add to the complexity and applicabihty of these processes and provide highly regulated cascades that mimic the power of enzymatic pathways. 

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