Effects of saturation and enzyme limitation in feedforward adaptive signal transduction.

In this study, the author examines the effects of saturation and enzyme limitation in temporal and spatial signal transduction in a generic feedforward adaptive module. The feedforward module encompasses a range of temporal and spatial signal processing, and this study systematically examines the effect of enzyme limitation/saturating effects in each of the feedforward pathways, and their interplay. It is found that this saturation makes the adaptation inexact, and this effect is more pronounced for higher levels of input signals. Further, it has a very significant role in affecting the temporal dynamics of this module. In examining the role of saturation in the module response to static gradients, the author finds that in certain cases, saturation can completely alter the gradient response. The author examines various aspects of the response systematically using analytical methods and simulations. Overall the author studies a framework and basis for examining and understanding the roles of saturating effects in multiple pathways involved in adaptive responses and sheds light on the relationship and connection between exact and inexact adaptation.